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Re: [ccd-newastro] Re: Cleaning my CCD camera

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  • Mark Striebeck
    Hi, This is a flat: http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg. My camera is a
    Message 1 of 20 , Mar 30, 2013
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      Hi,

      This is a flat:
      http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
      My camera is a starlight xpress H694.

      Sorry, I didn't mean to perform open heart surgery. I just want to clean
      the surfaces of the camera, lenses...

      MarkS


      On Sat, Mar 30, 2013 at 9:22 AM, Stan <stan_ccd@...> wrote:

      > **
      >
      >
      > (continued)
      >
      > For astro cameras the most difficult part of cleaning is the disassembly
      > and reassembly of the camera. It may require removing the shutter and it
      > definitely requires breaching the cold chamber, which will have to be
      > purged. If the cleaning environment is contaminated then you risk sealing
      > dust into the chamber and having it settle shortly afterwards. I've created
      > a make-shift clean room from a bathroom with the shower running (for some
      > time beforehand). The running water spray and humidity will remove a lot of
      > dust and de-ionize the environment. But of course the cold chamber and PC
      > boards can acquire water and require significant desiccation afterwards
      > (maybe 2 rounds of desiccation over a few days).
      >
      > Cleaning an astro CCD is a significant undertaking and should be put off
      > until truly necessary. Good flats can forestall the need for quite some
      > time.
      >
      > Stan
      >
      >
      >


      [Non-text portions of this message have been removed]
    • Terry Platt
      Hi Mark, Most of the particles appear to be on the outside surface of the front camera window. A gentle clean with a lens brush and air cannon should be all
      Message 2 of 20 , Mar 31, 2013
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        Hi Mark,

        Most of the particles appear to be on the outside surface of the front camera window. A gentle clean with a lens brush and air cannon should be all that it needs.

        Regards,
        Terry

        From: Mark Striebeck
        Sent: Sunday, March 31, 2013 7:51 AM
        To: ccd-newastro@yahoogroups.com
        Subject: Re: [ccd-newastro] Re: Cleaning my CCD camera


        Hi,

        This is a flat:
        http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
        My camera is a starlight xpress H694.

        Sorry, I didn't mean to perform open heart surgery. I just want to clean
        the surfaces of the camera, lenses...

        MarkS

        On Sat, Mar 30, 2013 at 9:22 AM, Stan <mailto:stan_ccd%40yahoo.com> wrote:

        > **
        >
        >
        > (continued)
        >
        > For astro cameras the most difficult part of cleaning is the disassembly
        > and reassembly of the camera. It may require removing the shutter and it
        > definitely requires breaching the cold chamber, which will have to be
        > purged. If the cleaning environment is contaminated then you risk sealing
        > dust into the chamber and having it settle shortly afterwards. I've created
        > a make-shift clean room from a bathroom with the shower running (for some
        > time beforehand). The running water spray and humidity will remove a lot of
        > dust and de-ionize the environment. But of course the cold chamber and PC
        > boards can acquire water and require significant desiccation afterwards
        > (maybe 2 rounds of desiccation over a few days).
        >
        > Cleaning an astro CCD is a significant undertaking and should be put off
        > until truly necessary. Good flats can forestall the need for quite some
        > time.
        >
        > Stan
        >
        >
        >

        [Non-text portions of this message have been removed]





        [Non-text portions of this message have been removed]
      • Roger Hamlett
        ... You need to be looking at a raw image (directly from the CCD). This is a clipped part, and possibly rescaled, so little use . Then count how many pixels
        Message 3 of 20 , Mar 31, 2013
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          > Hi,
          >
          > This is a flat:
          > http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
          > My camera is a starlight xpress H694.
          >
          > Sorry, I didn't mean to perform open heart surgery. I just want to clean
          > the surfaces of the camera, lenses...
          >
          > MarkS
          You need to be looking at a raw image (directly from the CCD). This is a
          clipped part, and possibly rescaled, so 'little use'.
          Then count how many pixels wide the blobs are. If you look there are a
          couple of very small ones, then a few slightly larger, and the rest are
          all about the same size. The big ones are about 130 pixels across
          (assuming you have not resized the image), the medium ones about 30
          pixels, and the smallest about 22 pixels. Now pixels on the H694, are
          4.54um across, so 99um, 136um, and 590um. Now a typical speck of dust is
          as small as a pixel, so 'straight away', the dust is not immediately on
          the CCD. How far away, depends on the f ratio of your scope. Assuming
          f/10, then the small specs are about 10mm away (I'd say the camera front
          window glass) Then the next lot a little further (have you got something
          like an IR blocker in the front of the camera?). Then the main number
          are a couple of inches from the CCD. The filters....

          Best Wishes
        • Stan
          ... Nearly all of those spots are outside the CCD chamber. The CCD itself looks very clean and you do not need to open the camera. But it wouldn t hurt to
          Message 4 of 20 , Mar 31, 2013
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            --- Mark Striebeck <mark.striebeck@...> wrote:
            > http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.

            Nearly all of those spots are outside the CCD chamber. The CCD itself looks very clean and you do not need to open the camera. But it wouldn't hurt to clean the camera window and filters, reducer, etc.

            Flats have very high S/N that reveals subtle contrasts not seen in normal light images. Most of those spots are probably barely visible or invisible in an unflatted light frame unless your sky pollution is substantial. A good flat should remove >98% of those effects from the light frame.

            Stan
          • echesak@flash.net
            Mark, Looking at your flat indicates to me that the majority of the particles are away from the CCD sensor. Only the very small patterns are on or near the
            Message 5 of 20 , Mar 31, 2013
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              Mark,

              Looking at your flat indicates to me that the majority of the particles are away from the CCD sensor. Only the very small patterns are on or near the level of the CCD sensor.

              You should have a look at this site, which will help you determine the distance from the sensor, where your particles lie.

              http://www.ccdware.com/resources/dust.cfm

              Without knowing your system, I'd suspect the filters or the mirror/corrector plate. The halo's that you are seeing are far too large for the majority of these to be on the sensor.

              Eric


              --- In ccd-newastro@yahoogroups.com, Mark Striebeck <mark.striebeck@...> wrote:
              >
              > Hi,
              >
              > This is a flat:
              > http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
              > My camera is a starlight xpress H694.
              >
              > Sorry, I didn't mean to perform open heart surgery. I just want to clean
              > the surfaces of the camera, lenses...
              >
              > MarkS
              >
              >
              > On Sat, Mar 30, 2013 at 9:22 AM, Stan <stan_ccd@...> wrote:
              >
              > > **
              > >
              > >
              > > (continued)
              > >
              > > For astro cameras the most difficult part of cleaning is the disassembly
              > > and reassembly of the camera. It may require removing the shutter and it
              > > definitely requires breaching the cold chamber, which will have to be
              > > purged. If the cleaning environment is contaminated then you risk sealing
              > > dust into the chamber and having it settle shortly afterwards. I've created
              > > a make-shift clean room from a bathroom with the shower running (for some
              > > time beforehand). The running water spray and humidity will remove a lot of
              > > dust and de-ionize the environment. But of course the cold chamber and PC
              > > boards can acquire water and require significant desiccation afterwards
              > > (maybe 2 rounds of desiccation over a few days).
              > >
              > > Cleaning an astro CCD is a significant undertaking and should be put off
              > > until truly necessary. Good flats can forestall the need for quite some
              > > time.
              > >
              > > Stan
              > >
              > >
              > >
              >
              >
              > [Non-text portions of this message have been removed]
              >
            • Mark Striebeck
              Eric, Thanks for that link - this will help a lot! MarkS ... [Non-text portions of this message have been removed]
              Message 6 of 20 , Mar 31, 2013
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                Eric,

                Thanks for that link - this will help a lot!

                MarkS


                On Sun, Mar 31, 2013 at 1:38 PM, echesak@... <echesak@...>wrote:

                > **
                >
                >
                >
                > Mark,
                >
                > Looking at your flat indicates to me that the majority of the particles
                > are away from the CCD sensor. Only the very small patterns are on or near
                > the level of the CCD sensor.
                >
                > You should have a look at this site, which will help you determine the
                > distance from the sensor, where your particles lie.
                >
                > http://www.ccdware.com/resources/dust.cfm
                >
                > Without knowing your system, I'd suspect the filters or the
                > mirror/corrector plate. The halo's that you are seeing are far too large
                > for the majority of these to be on the sensor.
                >
                > Eric
                >
                >
                > --- In ccd-newastro@yahoogroups.com, Mark Striebeck <mark.striebeck@...>
                > wrote:
                > >
                > > Hi,
                > >
                > > This is a flat:
                > >
                > http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
                > > My camera is a starlight xpress H694.
                > >
                > > Sorry, I didn't mean to perform open heart surgery. I just want to clean
                > > the surfaces of the camera, lenses...
                > >
                > > MarkS
                > >
                > >
                > > On Sat, Mar 30, 2013 at 9:22 AM, Stan <stan_ccd@...> wrote:
                > >
                > > > **
                >
                > > >
                > > >
                > > > (continued)
                > > >
                > > > For astro cameras the most difficult part of cleaning is the
                > disassembly
                > > > and reassembly of the camera. It may require removing the shutter and
                > it
                > > > definitely requires breaching the cold chamber, which will have to be
                > > > purged. If the cleaning environment is contaminated then you risk
                > sealing
                > > > dust into the chamber and having it settle shortly afterwards. I've
                > created
                > > > a make-shift clean room from a bathroom with the shower running (for
                > some
                > > > time beforehand). The running water spray and humidity will remove a
                > lot of
                > > > dust and de-ionize the environment. But of course the cold chamber and
                > PC
                > > > boards can acquire water and require significant desiccation afterwards
                > > > (maybe 2 rounds of desiccation over a few days).
                > > >
                > > > Cleaning an astro CCD is a significant undertaking and should be put
                > off
                > > > until truly necessary. Good flats can forestall the need for quite some
                > > > time.
                > > >
                > > > Stan
                > > >
                > > >
                > > >
                > >
                > >
                > > [Non-text portions of this message have been removed]
                > >
                >
                >
                >


                [Non-text portions of this message have been removed]
              • Mark Striebeck
                Putting in my values: 4.54 microns, 6.3 focal length, 200 pixels leads to 2.8 mm distance to ccd chip. I guess that means that most of these will be on the
                Message 7 of 20 , Mar 31, 2013
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                  Putting in my values: 4.54 microns, 6.3 focal length, 200 pixels leads to
                  2.8 mm distance to ccd chip. I guess that means that most of these will be
                  on the camera itself, right?

                  MarkS


                  On Sun, Mar 31, 2013 at 7:25 PM, Mark Striebeck <mark.striebeck@...>wrote:

                  > Eric,
                  >
                  > Thanks for that link - this will help a lot!
                  >
                  > MarkS
                  >
                  >
                  > On Sun, Mar 31, 2013 at 1:38 PM, echesak@... <echesak@...>wrote:
                  >
                  >> **
                  >>
                  >>
                  >>
                  >> Mark,
                  >>
                  >> Looking at your flat indicates to me that the majority of the particles
                  >> are away from the CCD sensor. Only the very small patterns are on or near
                  >> the level of the CCD sensor.
                  >>
                  >> You should have a look at this site, which will help you determine the
                  >> distance from the sensor, where your particles lie.
                  >>
                  >> http://www.ccdware.com/resources/dust.cfm
                  >>
                  >> Without knowing your system, I'd suspect the filters or the
                  >> mirror/corrector plate. The halo's that you are seeing are far too large
                  >> for the majority of these to be on the sensor.
                  >>
                  >> Eric
                  >>
                  >>
                  >> --- In ccd-newastro@yahoogroups.com, Mark Striebeck <mark.striebeck@...>
                  >> wrote:
                  >> >
                  >> > Hi,
                  >> >
                  >> > This is a flat:
                  >> >
                  >> http://4.bp.blogspot.com/-Io1SpMUp58M/USAU_1Nt4RI/AAAAAAAAhF8/00RMuLMFiWk/s1600/Flat+Master+-+luminescence+bin1x1.jpg.
                  >> > My camera is a starlight xpress H694.
                  >> >
                  >> > Sorry, I didn't mean to perform open heart surgery. I just want to clean
                  >> > the surfaces of the camera, lenses...
                  >> >
                  >> > MarkS
                  >> >
                  >> >
                  >> > On Sat, Mar 30, 2013 at 9:22 AM, Stan <stan_ccd@...> wrote:
                  >> >
                  >> > > **
                  >>
                  >> > >
                  >> > >
                  >> > > (continued)
                  >> > >
                  >> > > For astro cameras the most difficult part of cleaning is the
                  >> disassembly
                  >> > > and reassembly of the camera. It may require removing the shutter and
                  >> it
                  >> > > definitely requires breaching the cold chamber, which will have to be
                  >> > > purged. If the cleaning environment is contaminated then you risk
                  >> sealing
                  >> > > dust into the chamber and having it settle shortly afterwards. I've
                  >> created
                  >> > > a make-shift clean room from a bathroom with the shower running (for
                  >> some
                  >> > > time beforehand). The running water spray and humidity will remove a
                  >> lot of
                  >> > > dust and de-ionize the environment. But of course the cold chamber
                  >> and PC
                  >> > > boards can acquire water and require significant desiccation
                  >> afterwards
                  >> > > (maybe 2 rounds of desiccation over a few days).
                  >> > >
                  >> > > Cleaning an astro CCD is a significant undertaking and should be put
                  >> off
                  >> > > until truly necessary. Good flats can forestall the need for quite
                  >> some
                  >> > > time.
                  >> > >
                  >> > > Stan
                  >> > >
                  >> > >
                  >> > >
                  >> >
                  >> >
                  >> > [Non-text portions of this message have been removed]
                  >> >
                  >>
                  >>
                  >>
                  >
                  >


                  [Non-text portions of this message have been removed]
                • Stan
                  ... I don t see how (I ll talk to the creator of that calculator). Assuming the dust mote s actual diameter is insignificant then the distance should equal the
                  Message 8 of 20 , Apr 1, 2013
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                    --- Mark Striebeck <mark.striebeck@...> wrote:
                    > Putting in my values: 4.54 microns, 6.3 focal length,
                    > 200 pixels leads to 2.8 mm distance to ccd chip.

                    I don't see how (I'll talk to the creator of that calculator).

                    Assuming the dust mote's actual diameter is insignificant then the distance should equal the shadow diameter times the f-ratio, right? (simple geometry)

                    diam = 4.54u*200 = 0.9mm
                    distance = 0.9*6.3 = 5.7mm

                    BTW, here is another calculator:
                    http://www.wilmslowastro.com/software/formulae.htm#Dust

                    But 6mm is pretty close-in and may be inside the camera but is too far to be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is not reduced?

                    Try to find a build diagram of the camera to see what might be at that distance. Is there an internal filter wheel? Otherwise just assume that most of the dust is on the window and clean it.

                    Stan
                  • Mark Striebeck
                    Hi Stan, Thanks for the reply. Yes, thinking of it, it s hard to see how a small dust particle almost in front of the CCD camera could blow up so much. With
                    Message 9 of 20 , Apr 1, 2013
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                      Hi Stan,

                      Thanks for the reply. Yes, thinking of it, it's hard to see how a small
                      dust particle almost in front of the CCD camera could blow up so much. With
                      this other calculator I get a distance of 5.72mm - still small. But
                      couldn't this be on the optical window of the camera which is in front of
                      the chip?

                      I measured the diameter on a 1x1 binned raw image (i.e. no processing or
                      such) - I uploaded it here:
                      https://dl.dropbox.com/u/71789253/00012610.A.FlatField.fit.

                      My camera is a Starlight Xpress H694, the closest surface outside of the
                      camera is the filter in the filter wheel which is ~30mm from the chip.

                      MarkS


                      On Mon, Apr 1, 2013 at 8:45 AM, Stan <stan_ccd@...> wrote:

                      > **
                      >
                      >
                      > --- Mark Striebeck <mark.striebeck@...> wrote:
                      > > Putting in my values: 4.54 microns, 6.3 focal length,
                      > > 200 pixels leads to 2.8 mm distance to ccd chip.
                      >
                      > I don't see how (I'll talk to the creator of that calculator).
                      >
                      > Assuming the dust mote's actual diameter is insignificant then the
                      > distance should equal the shadow diameter times the f-ratio, right? (simple
                      > geometry)
                      >
                      > diam = 4.54u*200 = 0.9mm
                      > distance = 0.9*6.3 = 5.7mm
                      >
                      > BTW, here is another calculator:
                      > http://www.wilmslowastro.com/software/formulae.htm#Dust
                      >
                      > But 6mm is pretty close-in and may be inside the camera but is too far to
                      > be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is
                      > not reduced?
                      >
                      > Try to find a build diagram of the camera to see what might be at that
                      > distance. Is there an internal filter wheel? Otherwise just assume that
                      > most of the dust is on the window and clean it.
                      >
                      > Stan
                      >
                      >
                      >


                      [Non-text portions of this message have been removed]
                    • Terry Platt
                      Hi Stan & Mark, That’s about the distance between the CCD and the front window. I think that you will find that they are nearly all on the outer surface of
                      Message 10 of 20 , Apr 1, 2013
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                        Hi Stan & Mark,

                        That’s about the distance between the CCD and the front window. I think that you will find that they are nearly all on the outer surface of the camera window.

                        Regards,
                        Terry (SX Ltd)

                        From: Stan
                        Sent: Monday, April 01, 2013 4:45 PM
                        To: ccd-newastro@yahoogroups.com
                        Subject: [ccd-newastro] Re: Cleaning my CCD camera


                        --- Mark Striebeck <mark.striebeck@...> wrote:
                        > Putting in my values: 4.54 microns, 6.3 focal length,
                        > 200 pixels leads to 2.8 mm distance to ccd chip.

                        I don't see how (I'll talk to the creator of that calculator).

                        Assuming the dust mote's actual diameter is insignificant then the distance should equal the shadow diameter times the f-ratio, right? (simple geometry)

                        diam = 4.54u*200 = 0.9mm
                        distance = 0.9*6.3 = 5.7mm

                        BTW, here is another calculator:
                        http://www.wilmslowastro.com/software/formulae.htm#Dust

                        But 6mm is pretty close-in and may be inside the camera but is too far to be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is not reduced?

                        Try to find a build diagram of the camera to see what might be at that distance. Is there an internal filter wheel? Otherwise just assume that most of the dust is on the window and clean it.

                        Stan





                        [Non-text portions of this message have been removed]
                      • Mark Striebeck
                        Thanks Terry - that s what I figured. What is your (starlight xpress) recommended way to clean that window? I found contradicting recommendations: some say to
                        Message 11 of 20 , Apr 1, 2013
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                          Thanks Terry - that's what I figured.

                          What is your (starlight xpress) recommended way to clean that window? I
                          found contradicting recommendations: some say to clean with a (super) soft
                          brush (I have one that I use for cleaning my DSLR sensor that I keep sealed
                          at all times), others say that you should do it with (low) pressure air.

                          MarkS


                          On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <tplatt@...-uk.net>wrote:

                          > **
                          >
                          >
                          > Hi Stan & Mark,
                          >
                          > That�s about the distance between the CCD and the front window. I think
                          > that you will find that they are nearly all on the outer surface of the
                          > camera window.
                          >
                          > Regards,
                          > Terry (SX Ltd)
                          >
                          > From: Stan
                          > Sent: Monday, April 01, 2013 4:45 PM
                          > To: ccd-newastro@yahoogroups.com
                          > Subject: [ccd-newastro] Re: Cleaning my CCD camera
                          >
                          >
                          > --- Mark Striebeck <mark.striebeck@...> wrote:
                          > > Putting in my values: 4.54 microns, 6.3 focal length,
                          > > 200 pixels leads to 2.8 mm distance to ccd chip.
                          >
                          > I don't see how (I'll talk to the creator of that calculator).
                          >
                          > Assuming the dust mote's actual diameter is insignificant then the
                          > distance should equal the shadow diameter times the f-ratio, right? (simple
                          > geometry)
                          >
                          > diam = 4.54u*200 = 0.9mm
                          > distance = 0.9*6.3 = 5.7mm
                          >
                          > BTW, here is another calculator:
                          > http://www.wilmslowastro.com/software/formulae.htm#Dust
                          >
                          > But 6mm is pretty close-in and may be inside the camera but is too far to
                          > be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is
                          > not reduced?
                          >
                          > Try to find a build diagram of the camera to see what might be at that
                          > distance. Is there an internal filter wheel? Otherwise just assume that
                          > most of the dust is on the window and clean it.
                          >
                          > Stan
                          >
                          > [Non-text portions of this message have been removed]
                          >
                          >
                          >


                          [Non-text portions of this message have been removed]
                        • Ron Wodaski
                          The best way to clean any optical surface is wet. For the front window of just about any CCD camera (unless it leaks liquids badly), any pro-quality lens
                          Message 12 of 20 , Apr 1, 2013
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                            The best way to clean any optical surface is wet.

                            For the front window of just about any CCD camera (unless it leaks liquids badly), any pro-quality lens cleaning kit should do the job adequately.

                            By 'pro' in this context I mean a professional photographer; a professional astronomer would be more likely to use dangerous chemicals, such as acetone, to clean a flat surface. That's how we do it at the Tzec Maun Observatory. We also use industrial (not medical) grade gloves - they come quite a bit thicker than most medical gloves, which makes them safer for handling objects with metal edges, and are just as clean out of the box. Avoid gloves with various kinds of 'improvements' such as talc.

                            For optical surfaces, the key problems are various forms of adhesion - chemical bonding, electrostatic forces being the two most common you run into.

                            Chemical bonding occurs when dust or other particles get on the surface, and then the surface gets wet. It takes force to remove such dirt; a liquid facilitates removal both by helping to break the chemical bonds, and to lubricate the surface against scratches once stuff does get loose. Liquid also reduces/sliminates static charge.

                            it can be surprisingly hard to remove dust particles when static charge is present. I recall cleaning a sensor's cover plate once. It took me about 15 minutes; I was finally successful when I imagined my little brush to be a broom, and I carefully swept up the dust into a tiny tiny little pile, and then mechanically forced it against a second brush which acted as my 'dust pan'. <g> Otherwise, there are situations where you can brush and brush and brush and nothing ever seems to leave the surface. I've even watched through a magnifying glass as the material I brushed off the top of a cover slip jumped back onto the surface (from the brush, and from the side of the casing) as I lifted the brush.

                            Thus: wet cleaning is always the best approach. Still, you need to obtain the right materials (able to break those bonds, won't damage seals, etc.) and develop good techniques (gloves, disposal, etc.)

                            Ron Wodaski



                            On Apr 1, 2013, at 10:26 AM, Mark Striebeck <mark.striebeck@...> wrote:

                            > Thanks Terry - that's what I figured.
                            >
                            > What is your (starlight xpress) recommended way to clean that window? I
                            > found contradicting recommendations: some say to clean with a (super) soft
                            > brush (I have one that I use for cleaning my DSLR sensor that I keep sealed
                            > at all times), others say that you should do it with (low) pressure air.
                            >
                            > MarkS
                            >
                            >
                            > On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <tplatt@...-uk.net>wrote:
                            >
                            >> **
                            >>
                            >>
                            >> Hi Stan & Mark,
                            >>
                            >> That’s about the distance between the CCD and the front window. I think
                            >> that you will find that they are nearly all on the outer surface of the
                            >> camera window.
                            >>
                            >> Regards,
                            >> Terry (SX Ltd)
                            >>
                            >> From: Stan
                            >> Sent: Monday, April 01, 2013 4:45 PM
                            >> To: ccd-newastro@yahoogroups.com
                            >> Subject: [ccd-newastro] Re: Cleaning my CCD camera
                            >>
                            >>
                            >> --- Mark Striebeck <mark.striebeck@...> wrote:
                            >>> Putting in my values: 4.54 microns, 6.3 focal length,
                            >>> 200 pixels leads to 2.8 mm distance to ccd chip.
                            >>
                            >> I don't see how (I'll talk to the creator of that calculator).
                            >>
                            >> Assuming the dust mote's actual diameter is insignificant then the
                            >> distance should equal the shadow diameter times the f-ratio, right? (simple
                            >> geometry)
                            >>
                            >> diam = 4.54u*200 = 0.9mm
                            >> distance = 0.9*6.3 = 5.7mm
                            >>
                            >> BTW, here is another calculator:
                            >> http://www.wilmslowastro.com/software/formulae.htm#Dust
                            >>
                            >> But 6mm is pretty close-in and may be inside the camera but is too far to
                            >> be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is
                            >> not reduced?
                            >>
                            >> Try to find a build diagram of the camera to see what might be at that
                            >> distance. Is there an internal filter wheel? Otherwise just assume that
                            >> most of the dust is on the window and clean it.
                            >>
                            >> Stan
                            >>
                            >> [Non-text portions of this message have been removed]
                            >>
                            >>
                            >>
                            >
                            >
                            > [Non-text portions of this message have been removed]
                            >
                            >
                            >
                            > ------------------------------------
                            >
                            >
                            >
                            >
                          • Mark Striebeck
                            Hmmm, I found so many sources who warn from exactly this and recommend only dusting (e.g. http://www.arksky.org/asoclean.htm . And only revert to (liquid)
                            Message 13 of 20 , Apr 1, 2013
                            • 0 Attachment
                              Hmmm, I found so many sources who warn from exactly this and recommend only
                              dusting (e.g. http://www.arksky.org/asoclean.htm . And only revert to
                              (liquid) cleaning if absolutely necessary.


                              On Mon, Apr 1, 2013 at 10:43 AM, Ron Wodaski <yahoo@...> wrote:

                              > The best way to clean any optical surface is wet.
                              >
                              > For the front window of just about any CCD camera (unless it leaks liquids
                              > badly), any pro-quality lens cleaning kit should do the job adequately.
                              >
                              > By 'pro' in this context I mean a professional photographer; a
                              > professional astronomer would be more likely to use dangerous chemicals,
                              > such as acetone, to clean a flat surface. That's how we do it at the Tzec
                              > Maun Observatory. We also use industrial (not medical) grade gloves - they
                              > come quite a bit thicker than most medical gloves, which makes them safer
                              > for handling objects with metal edges, and are just as clean out of the
                              > box. Avoid gloves with various kinds of 'improvements' such as talc.
                              >
                              > For optical surfaces, the key problems are various forms of adhesion -
                              > chemical bonding, electrostatic forces being the two most common you run
                              > into.
                              >
                              > Chemical bonding occurs when dust or other particles get on the surface,
                              > and then the surface gets wet. It takes force to remove such dirt; a liquid
                              > facilitates removal both by helping to break the chemical bonds, and to
                              > lubricate the surface against scratches once stuff does get loose. Liquid
                              > also reduces/sliminates static charge.
                              >
                              > it can be surprisingly hard to remove dust particles when static charge is
                              > present. I recall cleaning a sensor's cover plate once. It took me about 15
                              > minutes; I was finally successful when I imagined my little brush to be a
                              > broom, and I carefully swept up the dust into a tiny tiny little pile, and
                              > then mechanically forced it against a second brush which acted as my 'dust
                              > pan'. <g> Otherwise, there are situations where you can brush and brush and
                              > brush and nothing ever seems to leave the surface. I've even watched
                              > through a magnifying glass as the material I brushed off the top of a cover
                              > slip jumped back onto the surface (from the brush, and from the side of the
                              > casing) as I lifted the brush.
                              >
                              > Thus: wet cleaning is always the best approach. Still, you need to obtain
                              > the right materials (able to break those bonds, won't damage seals, etc.)
                              > and develop good techniques (gloves, disposal, etc.)
                              >
                              > Ron Wodaski
                              >
                              >
                              >
                              > On Apr 1, 2013, at 10:26 AM, Mark Striebeck <mark.striebeck@...>
                              > wrote:
                              >
                              > > Thanks Terry - that's what I figured.
                              > >
                              > > What is your (starlight xpress) recommended way to clean that window? I
                              > > found contradicting recommendations: some say to clean with a (super)
                              > soft
                              > > brush (I have one that I use for cleaning my DSLR sensor that I keep
                              > sealed
                              > > at all times), others say that you should do it with (low) pressure air.
                              > >
                              > > MarkS
                              > >
                              > >
                              > > On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <
                              > tplatt@...-uk.net>wrote:
                              > >
                              > >> **
                              > >>
                              > >>
                              > >> Hi Stan & Mark,
                              > >>
                              > >> That�s about the distance between the CCD and the front window. I think
                              > >> that you will find that they are nearly all on the outer surface of the
                              > >> camera window.
                              > >>
                              > >> Regards,
                              > >> Terry (SX Ltd)
                              > >>
                              > >> From: Stan
                              > >> Sent: Monday, April 01, 2013 4:45 PM
                              > >> To: ccd-newastro@yahoogroups.com
                              > >> Subject: [ccd-newastro] Re: Cleaning my CCD camera
                              > >>
                              > >>
                              > >> --- Mark Striebeck <mark.striebeck@...> wrote:
                              > >>> Putting in my values: 4.54 microns, 6.3 focal length,
                              > >>> 200 pixels leads to 2.8 mm distance to ccd chip.
                              > >>
                              > >> I don't see how (I'll talk to the creator of that calculator).
                              > >>
                              > >> Assuming the dust mote's actual diameter is insignificant then the
                              > >> distance should equal the shadow diameter times the f-ratio, right?
                              > (simple
                              > >> geometry)
                              > >>
                              > >> diam = 4.54u*200 = 0.9mm
                              > >> distance = 0.9*6.3 = 5.7mm
                              > >>
                              > >> BTW, here is another calculator:
                              > >> http://www.wilmslowastro.com/software/formulae.htm#Dust
                              > >>
                              > >> But 6mm is pretty close-in and may be inside the camera but is too far
                              > to
                              > >> be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG
                              > is
                              > >> not reduced?
                              > >>
                              > >> Try to find a build diagram of the camera to see what might be at that
                              > >> distance. Is there an internal filter wheel? Otherwise just assume that
                              > >> most of the dust is on the window and clean it.
                              > >>
                              > >> Stan
                              > >>
                              > >> [Non-text portions of this message have been removed]
                              > >>
                              > >>
                              > >>
                              > >
                              > >
                              > > [Non-text portions of this message have been removed]
                              > >
                              > >
                              > >
                              > > ------------------------------------
                              > >
                              > >
                              > >
                              > >
                              >
                              >
                              >
                              > ------------------------------------
                              >
                              >
                              >
                              >
                              >


                              [Non-text portions of this message have been removed]
                            • Ron Wodaski
                              I didn t find anything on that link that is opposed to what I was saying. Their remonstrance about dusting is really only saying: if there is stuff that is not
                              Message 14 of 20 , Apr 1, 2013
                              • 0 Attachment
                                I didn't find anything on that link that is opposed to what I was saying. Their remonstrance about dusting is really only saying: if there is stuff that is not chemically bonded, yeah, go ahead and remove that first.

                                I certainly wasn't suggesting you should clean when it's not necessary. <g>

                                Ron Wodaski



                                On Apr 1, 2013, at 10:58 AM, Mark Striebeck <mark.striebeck@...> wrote:

                                > Hmmm, I found so many sources who warn from exactly this and recommend only
                                > dusting (e.g. http://www.arksky.org/asoclean.htm . And only revert to
                                > (liquid) cleaning if absolutely necessary.
                                >
                                >
                                > On Mon, Apr 1, 2013 at 10:43 AM, Ron Wodaski <yahoo@...> wrote:
                                >
                                >> The best way to clean any optical surface is wet.
                                >>
                                >> For the front window of just about any CCD camera (unless it leaks liquids
                                >> badly), any pro-quality lens cleaning kit should do the job adequately.
                                >>
                                >> By 'pro' in this context I mean a professional photographer; a
                                >> professional astronomer would be more likely to use dangerous chemicals,
                                >> such as acetone, to clean a flat surface. That's how we do it at the Tzec
                                >> Maun Observatory. We also use industrial (not medical) grade gloves - they
                                >> come quite a bit thicker than most medical gloves, which makes them safer
                                >> for handling objects with metal edges, and are just as clean out of the
                                >> box. Avoid gloves with various kinds of 'improvements' such as talc.
                                >>
                                >> For optical surfaces, the key problems are various forms of adhesion -
                                >> chemical bonding, electrostatic forces being the two most common you run
                                >> into.
                                >>
                                >> Chemical bonding occurs when dust or other particles get on the surface,
                                >> and then the surface gets wet. It takes force to remove such dirt; a liquid
                                >> facilitates removal both by helping to break the chemical bonds, and to
                                >> lubricate the surface against scratches once stuff does get loose. Liquid
                                >> also reduces/sliminates static charge.
                                >>
                                >> it can be surprisingly hard to remove dust particles when static charge is
                                >> present. I recall cleaning a sensor's cover plate once. It took me about 15
                                >> minutes; I was finally successful when I imagined my little brush to be a
                                >> broom, and I carefully swept up the dust into a tiny tiny little pile, and
                                >> then mechanically forced it against a second brush which acted as my 'dust
                                >> pan'. <g> Otherwise, there are situations where you can brush and brush and
                                >> brush and nothing ever seems to leave the surface. I've even watched
                                >> through a magnifying glass as the material I brushed off the top of a cover
                                >> slip jumped back onto the surface (from the brush, and from the side of the
                                >> casing) as I lifted the brush.
                                >>
                                >> Thus: wet cleaning is always the best approach. Still, you need to obtain
                                >> the right materials (able to break those bonds, won't damage seals, etc.)
                                >> and develop good techniques (gloves, disposal, etc.)
                                >>
                                >> Ron Wodaski
                                >>
                                >>
                                >>
                                >> On Apr 1, 2013, at 10:26 AM, Mark Striebeck <mark.striebeck@...>
                                >> wrote:
                                >>
                                >>> Thanks Terry - that's what I figured.
                                >>>
                                >>> What is your (starlight xpress) recommended way to clean that window? I
                                >>> found contradicting recommendations: some say to clean with a (super)
                                >> soft
                                >>> brush (I have one that I use for cleaning my DSLR sensor that I keep
                                >> sealed
                                >>> at all times), others say that you should do it with (low) pressure air.
                                >>>
                                >>> MarkS
                                >>>
                                >>>
                                >>> On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <
                                >> tplatt@...-uk.net>wrote:
                                >>>
                                >>>> **
                                >>>>
                                >>>>
                                >>>> Hi Stan & Mark,
                                >>>>
                                >>>> That’s about the distance between the CCD and the front window. I think
                                >>>> that you will find that they are nearly all on the outer surface of the
                                >>>> camera window.
                                >>>>
                                >>>> Regards,
                                >>>> Terry (SX Ltd)
                                >>>>
                                >>>> From: Stan
                                >>>> Sent: Monday, April 01, 2013 4:45 PM
                                >>>> To: ccd-newastro@yahoogroups.com
                                >>>> Subject: [ccd-newastro] Re: Cleaning my CCD camera
                                >>>>
                                >>>>
                                >>>> --- Mark Striebeck <mark.striebeck@...> wrote:
                                >>>>> Putting in my values: 4.54 microns, 6.3 focal length,
                                >>>>> 200 pixels leads to 2.8 mm distance to ccd chip.
                                >>>>
                                >>>> I don't see how (I'll talk to the creator of that calculator).
                                >>>>
                                >>>> Assuming the dust mote's actual diameter is insignificant then the
                                >>>> distance should equal the shadow diameter times the f-ratio, right?
                                >> (simple
                                >>>> geometry)
                                >>>>
                                >>>> diam = 4.54u*200 = 0.9mm
                                >>>> distance = 0.9*6.3 = 5.7mm
                                >>>>
                                >>>> BTW, here is another calculator:
                                >>>> http://www.wilmslowastro.com/software/formulae.htm#Dust
                                >>>>
                                >>>> But 6mm is pretty close-in and may be inside the camera but is too far
                                >> to
                                >>>> be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG
                                >> is
                                >>>> not reduced?
                                >>>>
                                >>>> Try to find a build diagram of the camera to see what might be at that
                                >>>> distance. Is there an internal filter wheel? Otherwise just assume that
                                >>>> most of the dust is on the window and clean it.
                                >>>>
                                >>>> Stan
                                >>>>
                                >>>> [Non-text portions of this message have been removed]
                                >>>>
                                >>>>
                                >>>>
                                >>>
                                >>>
                                >>> [Non-text portions of this message have been removed]
                                >>>
                                >>>
                                >>>
                                >>> ------------------------------------
                                >>>
                                >>>
                                >>>
                                >>>
                                >>
                                >>
                                >>
                                >> ------------------------------------
                                >>
                                >>
                                >>
                                >>
                                >>
                                >
                                >
                                > [Non-text portions of this message have been removed]
                                >
                                >
                                >
                                > ------------------------------------
                                >
                                >
                                >
                                >
                              • phils67
                                Many many years ago, when I was doing my own B/W photo printing, I had a special dust brush for cleaning off negatives. Static would normally cause the dust
                                Message 15 of 20 , Apr 2, 2013
                                • 0 Attachment
                                  Many many years ago, when I was doing my own B/W photo printing, I had a special dust brush for cleaning off negatives. Static would normally cause the dust particles to return to the negative so the brush had a radioactive emitter strip that eliminated static charges as you wiped off the dust. The strip had a life of only a few years and was an alpha particle emitter. It worked very well.

                                  Phil

                                  --- In ccd-newastro@yahoogroups.com, Ron Wodaski <yahoo@...> wrote:
                                  >
                                  > The best way to clean any optical surface is wet.
                                  >
                                  > For the front window of just about any CCD camera (unless it leaks liquids badly), any pro-quality lens cleaning kit should do the job adequately.
                                  >
                                  > By 'pro' in this context I mean a professional photographer; a professional astronomer would be more likely to use dangerous chemicals, such as acetone, to clean a flat surface. That's how we do it at the Tzec Maun Observatory. We also use industrial (not medical) grade gloves - they come quite a bit thicker than most medical gloves, which makes them safer for handling objects with metal edges, and are just as clean out of the box. Avoid gloves with various kinds of 'improvements' such as talc.
                                  >
                                  > For optical surfaces, the key problems are various forms of adhesion - chemical bonding, electrostatic forces being the two most common you run into.
                                  >
                                  > Chemical bonding occurs when dust or other particles get on the surface, and then the surface gets wet. It takes force to remove such dirt; a liquid facilitates removal both by helping to break the chemical bonds, and to lubricate the surface against scratches once stuff does get loose. Liquid also reduces/sliminates static charge.
                                  >
                                  > it can be surprisingly hard to remove dust particles when static charge is present. I recall cleaning a sensor's cover plate once. It took me about 15 minutes; I was finally successful when I imagined my little brush to be a broom, and I carefully swept up the dust into a tiny tiny little pile, and then mechanically forced it against a second brush which acted as my 'dust pan'. <g> Otherwise, there are situations where you can brush and brush and brush and nothing ever seems to leave the surface. I've even watched through a magnifying glass as the material I brushed off the top of a cover slip jumped back onto the surface (from the brush, and from the side of the casing) as I lifted the brush.
                                  >
                                  > Thus: wet cleaning is always the best approach. Still, you need to obtain the right materials (able to break those bonds, won't damage seals, etc.) and develop good techniques (gloves, disposal, etc.)
                                  >
                                  > Ron Wodaski
                                  >
                                  >
                                  >
                                  > On Apr 1, 2013, at 10:26 AM, Mark Striebeck <mark.striebeck@...> wrote:
                                  >
                                  > > Thanks Terry - that's what I figured.
                                  > >
                                  > > What is your (starlight xpress) recommended way to clean that window? I
                                  > > found contradicting recommendations: some say to clean with a (super) soft
                                  > > brush (I have one that I use for cleaning my DSLR sensor that I keep sealed
                                  > > at all times), others say that you should do it with (low) pressure air.
                                  > >
                                  > > MarkS
                                  > >
                                  > >
                                  > > On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <tplatt@...>wrote:
                                  > >
                                  > >> **
                                  > >>
                                  > >>
                                  > >> Hi Stan & Mark,
                                  > >>
                                  > >> That's about the distance between the CCD and the front window. I think
                                  > >> that you will find that they are nearly all on the outer surface of the
                                  > >> camera window.
                                  > >>
                                  > >> Regards,
                                  > >> Terry (SX Ltd)
                                  > >>
                                  > >> From: Stan
                                  > >> Sent: Monday, April 01, 2013 4:45 PM
                                  > >> To: ccd-newastro@yahoogroups.com
                                  > >> Subject: [ccd-newastro] Re: Cleaning my CCD camera
                                  > >>
                                  > >>
                                  > >> --- Mark Striebeck <mark.striebeck@> wrote:
                                  > >>> Putting in my values: 4.54 microns, 6.3 focal length,
                                  > >>> 200 pixels leads to 2.8 mm distance to ccd chip.
                                  > >>
                                  > >> I don't see how (I'll talk to the creator of that calculator).
                                  > >>
                                  > >> Assuming the dust mote's actual diameter is insignificant then the
                                  > >> distance should equal the shadow diameter times the f-ratio, right? (simple
                                  > >> geometry)
                                  > >>
                                  > >> diam = 4.54u*200 = 0.9mm
                                  > >> distance = 0.9*6.3 = 5.7mm
                                  > >>
                                  > >> BTW, here is another calculator:
                                  > >> http://www.wilmslowastro.com/software/formulae.htm#Dust
                                  > >>
                                  > >> But 6mm is pretty close-in and may be inside the camera but is too far to
                                  > >> be on the coverslip. Are you sure that flat is binned 1x1 and that JPEG is
                                  > >> not reduced?
                                  > >>
                                  > >> Try to find a build diagram of the camera to see what might be at that
                                  > >> distance. Is there an internal filter wheel? Otherwise just assume that
                                  > >> most of the dust is on the window and clean it.
                                  > >>
                                  > >> Stan
                                  > >>
                                  > >> [Non-text portions of this message have been removed]
                                  > >>
                                  > >>
                                  > >>
                                  > >
                                  > >
                                  > > [Non-text portions of this message have been removed]
                                  > >
                                  > >
                                  > >
                                  > > ------------------------------------
                                  > >
                                  > >
                                  > >
                                  > >
                                  >
                                • Mark Striebeck
                                  So, all I did was to clean the camera window with some air (not compressed, but with a little bellows that I normally use for my DSLR) and then with a DSLR
                                  Message 16 of 20 , Apr 6, 2013
                                  • 0 Attachment
                                    So, all I did was to clean the camera window with some air (not compressed,
                                    but with a little bellows that I normally use for my DSLR) and then with a
                                    DSLR cleaning brush (which I always keep sealed). And now my flats look
                                    like this:
                                    http://3.bp.blogspot.com/-2LOuEM_EUYo/UWD5yTIFzkI/AAAAAAAAinM/huB9RuJGF1Y/s320/00013383.jpg

                                    I wish all problems would be so easy to fix ...

                                    Thanks for all the advice.

                                    MarkS


                                    On Tue, Apr 2, 2013 at 6:48 AM, phils67 <plsherman@...> wrote:

                                    > **
                                    >
                                    >
                                    > Many many years ago, when I was doing my own B/W photo printing, I had a
                                    > special dust brush for cleaning off negatives. Static would normally cause
                                    > the dust particles to return to the negative so the brush had a radioactive
                                    > emitter strip that eliminated static charges as you wiped off the dust. The
                                    > strip had a life of only a few years and was an alpha particle emitter. It
                                    > worked very well.
                                    >
                                    > Phil
                                    >
                                    >
                                    > --- In ccd-newastro@yahoogroups.com, Ron Wodaski <yahoo@...> wrote:
                                    > >
                                    > > The best way to clean any optical surface is wet.
                                    > >
                                    > > For the front window of just about any CCD camera (unless it leaks
                                    > liquids badly), any pro-quality lens cleaning kit should do the job
                                    > adequately.
                                    > >
                                    > > By 'pro' in this context I mean a professional photographer; a
                                    > professional astronomer would be more likely to use dangerous chemicals,
                                    > such as acetone, to clean a flat surface. That's how we do it at the Tzec
                                    > Maun Observatory. We also use industrial (not medical) grade gloves - they
                                    > come quite a bit thicker than most medical gloves, which makes them safer
                                    > for handling objects with metal edges, and are just as clean out of the
                                    > box. Avoid gloves with various kinds of 'improvements' such as talc.
                                    > >
                                    > > For optical surfaces, the key problems are various forms of adhesion -
                                    > chemical bonding, electrostatic forces being the two most common you run
                                    > into.
                                    > >
                                    > > Chemical bonding occurs when dust or other particles get on the surface,
                                    > and then the surface gets wet. It takes force to remove such dirt; a liquid
                                    > facilitates removal both by helping to break the chemical bonds, and to
                                    > lubricate the surface against scratches once stuff does get loose. Liquid
                                    > also reduces/sliminates static charge.
                                    > >
                                    > > it can be surprisingly hard to remove dust particles when static charge
                                    > is present. I recall cleaning a sensor's cover plate once. It took me about
                                    > 15 minutes; I was finally successful when I imagined my little brush to be
                                    > a broom, and I carefully swept up the dust into a tiny tiny little pile,
                                    > and then mechanically forced it against a second brush which acted as my
                                    > 'dust pan'. <g> Otherwise, there are situations where you can brush and
                                    > brush and brush and nothing ever seems to leave the surface. I've even
                                    > watched through a magnifying glass as the material I brushed off the top of
                                    > a cover slip jumped back onto the surface (from the brush, and from the
                                    > side of the casing) as I lifted the brush.
                                    > >
                                    > > Thus: wet cleaning is always the best approach. Still, you need to
                                    > obtain the right materials (able to break those bonds, won't damage seals,
                                    > etc.) and develop good techniques (gloves, disposal, etc.)
                                    > >
                                    > > Ron Wodaski
                                    > >
                                    > >
                                    > >
                                    > > On Apr 1, 2013, at 10:26 AM, Mark Striebeck <mark.striebeck@...> wrote:
                                    > >
                                    > > > Thanks Terry - that's what I figured.
                                    > > >
                                    > > > What is your (starlight xpress) recommended way to clean that window? I
                                    > > > found contradicting recommendations: some say to clean with a (super)
                                    > soft
                                    > > > brush (I have one that I use for cleaning my DSLR sensor that I keep
                                    > sealed
                                    > > > at all times), others say that you should do it with (low) pressure
                                    > air.
                                    > > >
                                    > > > MarkS
                                    > > >
                                    > > >
                                    > > > On Mon, Apr 1, 2013 at 10:14 AM, Terry Platt <tplatt@...>wrote:
                                    >
                                    > > >
                                    > > >> **
                                    > > >>
                                    > > >>
                                    > > >> Hi Stan & Mark,
                                    > > >>
                                    > > >> That's about the distance between the CCD and the front window. I
                                    > think
                                    > > >> that you will find that they are nearly all on the outer surface of
                                    > the
                                    > > >> camera window.
                                    > > >>
                                    > > >> Regards,
                                    > > >> Terry (SX Ltd)
                                    > > >>
                                    > > >> From: Stan
                                    > > >> Sent: Monday, April 01, 2013 4:45 PM
                                    > > >> To: ccd-newastro@yahoogroups.com
                                    > > >> Subject: [ccd-newastro] Re: Cleaning my CCD camera
                                    > > >>
                                    > > >>
                                    > > >> --- Mark Striebeck <mark.striebeck@> wrote:
                                    > > >>> Putting in my values: 4.54 microns, 6.3 focal length,
                                    > > >>> 200 pixels leads to 2.8 mm distance to ccd chip.
                                    > > >>
                                    > > >> I don't see how (I'll talk to the creator of that calculator).
                                    > > >>
                                    > > >> Assuming the dust mote's actual diameter is insignificant then the
                                    > > >> distance should equal the shadow diameter times the f-ratio, right?
                                    > (simple
                                    > > >> geometry)
                                    > > >>
                                    > > >> diam = 4.54u*200 = 0.9mm
                                    > > >> distance = 0.9*6.3 = 5.7mm
                                    > > >>
                                    > > >> BTW, here is another calculator:
                                    > > >> http://www.wilmslowastro.com/software/formulae.htm#Dust
                                    > > >>
                                    > > >> But 6mm is pretty close-in and may be inside the camera but is too
                                    > far to
                                    > > >> be on the coverslip. Are you sure that flat is binned 1x1 and that
                                    > JPEG is
                                    > > >> not reduced?
                                    > > >>
                                    > > >> Try to find a build diagram of the camera to see what might be at that
                                    > > >> distance. Is there an internal filter wheel? Otherwise just assume
                                    > that
                                    > > >> most of the dust is on the window and clean it.
                                    > > >>
                                    > > >> Stan
                                    > > >>
                                    > > >> [Non-text portions of this message have been removed]
                                    > > >>
                                    > > >>
                                    > > >>
                                    > > >
                                    > > >
                                    > > > [Non-text portions of this message have been removed]
                                    > > >
                                    > > >
                                    > > >
                                    > > > ------------------------------------
                                    > > >
                                    > > >
                                    > > >
                                    > > >
                                    > >
                                    >
                                    >
                                    >


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