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Re: [ccd-newastro] New to CCD Astrophotography: Master Dark/Master Bias?

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  • jfmiller7@comcast.net
    Would not a dark frame already have bias data in it? regards , Jim ... From: Douglas B. George To: ccd-newastro@ yahoogroups .com Sent:
    Message 1 of 17 , Oct 25, 2010
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      Would not a dark frame already have bias data in it?



      regards ,



      Jim
      ----- Original Message -----
      From: "Douglas B. George" < dg @...>
      To: ccd-newastro@ yahoogroups .com
      Sent: Monday, October 25, 2010 2:26:47 PM
      Subject: Re: [ccd-newastro] New to CCD Astrophotography : Master Dark/Master Bias?

       




      On 2010-10-25 11:43 AM, Neil Fleming wrote:

      > * The sources I've read suggest subtracting the bias frame from each dark
      > sub-frame before combining them. But couldn't I combine, then subtract just
      > once? Or is there a quirk of the algorithm that makes that a bad idea?

      That's a REALLY bad idea. Not because of any quirk, but because MaxIm DL
      handles that automatically. Doing it manually will probably result in it being
      done TWICE, which would be bad.

      The Set Calibration command is designed to handle everything automatically.
      Just dump in all of your calibration frames and let it figure out the details.

      Doug

      --

      Doug George
      dgeorge @...

      Diffraction Limited
      Makers of Cyanogen Imaging Products
      http :// www .cyanogen.com/

      100 Craig Henry Dr., Suite 202
      Ottawa, Ontario,
      Canada, K2G 5W3

      Phone: (613) 225-2732
      Fax: (613) 225-9688



      [Non-text portions of this message have been removed]
    • Mike
      Hi Group, I have a 12 SCT with a ST10XME camera at F/6.7 and, mounted piggyback on that scope, a 102mm F/6.9 refractor with an ST2000XM camera attached to it.
      Message 2 of 17 , Nov 2, 2010
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        Hi Group,



        I have a 12" SCT with a ST10XME camera at F/6.7 and, mounted piggyback on that scope, a 102mm F/6.9 refractor with an ST2000XM camera attached to it. I want to use the refractor as a guide scope. According to my calculations (from Ron's CCD Calculator), the pixel scales for each optical configuration are:



        1.38 arcsecs/pixel for the SCT (with 2x binning)

        4.33 arcsecs/pixel for the refractor (with 2x binning)



        I have been having at best mediocre results guiding with the refractor. I'm using MaximDL for imaging/guiding.



        For me to achieve the best guider corrections, should I make any changes to the above configuration? Should I not use 2x binning with the guide scope (and thus have about 2.16 arcsecs per pixel? What is the ideal configuration given the pixel scale of the main scope?





        Thanks,

        -Mike Renzi



        [Non-text portions of this message have been removed]
      • Ron Wodaski
        Most likely, you have run into the primary issue with an external guider: differential flexure. All optical systems flex as you slew the scope. And an SCT can
        Message 3 of 17 , Nov 2, 2010
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          Most likely, you have run into the primary issue with an external guider: differential flexure.

          All optical systems flex as you slew the scope. And an SCT can be especially problematic, since the primary mirror floats on its support, and is therefore not fixed.

          The problem is that each optical system has it's own reaction to the changing direction of gravity, and will flex in different ways, at different rates.

          You can secure each optical system better to get improvement. However, if a scope has internal flexure - such as most SCTs do - you may not be able to get rid of the differential flexure easily, and sometimes not at all.

          Ron Wodaski



          On Nov 2, 2010, at 12:06 PM, Mike wrote:

          > Hi Group,
          >
          >
          >
          > I have a 12" SCT with a ST10XME camera at F/6.7 and, mounted piggyback on that scope, a 102mm F/6.9 refractor with an ST2000XM camera attached to it. I want to use the refractor as a guide scope. According to my calculations (from Ron's CCD Calculator), the pixel scales for each optical configuration are:
          >
          >
          >
          > 1.38 arcsecs/pixel for the SCT (with 2x binning)
          >
          > 4.33 arcsecs/pixel for the refractor (with 2x binning)
          >
          >
          >
          > I have been having at best mediocre results guiding with the refractor. I'm using MaximDL for imaging/guiding.
          >
          >
          >
          > For me to achieve the best guider corrections, should I make any changes to the above configuration? Should I not use 2x binning with the guide scope (and thus have about 2.16 arcsecs per pixel? What is the ideal configuration given the pixel scale of the main scope?
          >
          >
          >
          >
          >
          > Thanks,
          >
          > -Mike Renzi
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
          >
          >
          > ------------------------------------
          >
          >
          >
          >
        • evwark
          It would! But that s the problem. You don t want to take a new dark frame with every picture you take, so it s better to just take a master dark that you use
          Message 4 of 17 , Nov 2, 2010
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            It would! But that's the problem. You don't want to take a new dark frame with every picture you take, so it's better to just take a master dark that you use again and again. But since light exposures aren't always all the same duration, you need to scale the dark frame (10m dark, 5m light? Just divide the dark pixel values in half!). But bias data doesn't scale, and if you leave it in, you can't scale the dark. Hence the subtraction.

            Of course, as I've learned, Maxim DL does all of that automatically. I'm just blown away by this software. It really does absolutely everything...

            --- In ccd-newastro@yahoogroups.com, jfmiller7@... wrote:
            >
            >
            >
            > Would not a dark frame already have bias data in it?
            >
            >
            >
            > regards ,
            >
            >
            >
            > Jim
            > ----- Original Message -----
            > From: "Douglas B. George" < dg @...>
            > To: ccd-newastro@ yahoogroups .com
            > Sent: Monday, October 25, 2010 2:26:47 PM
            > Subject: Re: [ccd-newastro] New to CCD Astrophotography : Master Dark/Master Bias?
            >
            >  
            >
            >
            >
            >
            > On 2010-10-25 11:43 AM, Neil Fleming wrote:
            >
            > > * The sources I've read suggest subtracting the bias frame from each dark
            > > sub-frame before combining them. But couldn't I combine, then subtract just
            > > once? Or is there a quirk of the algorithm that makes that a bad idea?
            >
            > That's a REALLY bad idea. Not because of any quirk, but because MaxIm DL
            > handles that automatically. Doing it manually will probably result in it being
            > done TWICE, which would be bad.
            >
            > The Set Calibration command is designed to handle everything automatically.
            > Just dump in all of your calibration frames and let it figure out the details.
            >
            > Doug
            >
            > --
            >
            > Doug George
            > dgeorge @...
            >
            > Diffraction Limited
            > Makers of Cyanogen Imaging Products
            > http :// www .cyanogen.com/
            >
            > 100 Craig Henry Dr., Suite 202
            > Ottawa, Ontario,
            > Canada, K2G 5W3
            >
            > Phone: (613) 225-2732
            > Fax: (613) 225-9688
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • dmwmpd
            Hi Mike, The mirror flop tendency with SCT scopes makes using a separate guide scope almost impossible. Using an Off Axis Guider (OAG) is the general
            Message 5 of 17 , Nov 2, 2010
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              Hi Mike,

              The mirror flop tendency with SCT scopes makes using a separate guide scope almost impossible. Using an Off Axis Guider (OAG) is the general recommended solution because the guider is looking through the same scope optics as the image camera. Using an OAG isn't as easy as a separate guide scope, but will solve your flexure problem.

              Don

              --- In ccd-newastro@yahoogroups.com, Ron Wodaski <yahoo@...> wrote:
              >
              > Most likely, you have run into the primary issue with an external guider: differential flexure.
              >
              > All optical systems flex as you slew the scope. And an SCT can be especially problematic, since the primary mirror floats on its support, and is therefore not fixed.
              >
              > The problem is that each optical system has it's own reaction to the changing direction of gravity, and will flex in different ways, at different rates.
              >
              > You can secure each optical system better to get improvement. However, if a scope has internal flexure - such as most SCTs do - you may not be able to get rid of the differential flexure easily, and sometimes not at all.
              >
              > Ron Wodaski
              >
              >
              >
              > On Nov 2, 2010, at 12:06 PM, Mike wrote:
              >
              > > Hi Group,
              > >
              > >
              > >
              > > I have a 12" SCT with a ST10XME camera at F/6.7 and, mounted piggyback on that scope, a 102mm F/6.9 refractor with an ST2000XM camera attached to it. I want to use the refractor as a guide scope. According to my calculations (from Ron's CCD Calculator), the pixel scales for each optical configuration are:
              > >
              > >
              > >
              > > 1.38 arcsecs/pixel for the SCT (with 2x binning)
              > >
              > > 4.33 arcsecs/pixel for the refractor (with 2x binning)
              > >
              > >
              > >
              > > I have been having at best mediocre results guiding with the refractor. I'm using MaximDL for imaging/guiding.
              > >
              > >
              > >
              > > For me to achieve the best guider corrections, should I make any changes to the above configuration? Should I not use 2x binning with the guide scope (and thus have about 2.16 arcsecs per pixel? What is the ideal configuration given the pixel scale of the main scope?
              > >
              > >
              > >
              > >
              > >
              > > Thanks,
              > >
              > > -Mike Renzi
              > >
              > >
              > >
              > > [Non-text portions of this message have been removed]
              > >
              > >
              > >
              > > ------------------------------------
              > >
              > >
              > >
              > >
              >
            • Ron Wodaski
              Here s yet another way to look at it. A bias frame records the value in every pixel at the start of an exposure. A dark frame records the value in every pixel
              Message 6 of 17 , Nov 2, 2010
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                Here's yet another way to look at it.

                A bias frame records the value in every pixel at the start of an exposure.

                A dark frame records the value in every pixel at the end of an exposure.

                To scale what happened during the exposure, you must subtract the starting values from the final values.

                Ron Wodaski



                On Nov 2, 2010, at 2:15 PM, evwark wrote:

                > It would! But that's the problem. You don't want to take a new dark frame with every picture you take, so it's better to just take a master dark that you use again and again. But since light exposures aren't always all the same duration, you need to scale the dark frame (10m dark, 5m light? Just divide the dark pixel values in half!). But bias data doesn't scale, and if you leave it in, you can't scale the dark. Hence the subtraction.
                >
                > Of course, as I've learned, Maxim DL does all of that automatically. I'm just blown away by this software. It really does absolutely everything...
                >
                > --- In ccd-newastro@yahoogroups.com, jfmiller7@... wrote:
                >>
                >>
                >>
                >> Would not a dark frame already have bias data in it?
                >>
                >>
                >>
                >> regards ,
                >>
                >>
                >>
                >> Jim
                >> ----- Original Message -----
                >> From: "Douglas B. George" < dg @...>
                >> To: ccd-newastro@ yahoogroups .com
                >> Sent: Monday, October 25, 2010 2:26:47 PM
                >> Subject: Re: [ccd-newastro] New to CCD Astrophotography : Master Dark/Master Bias?
                >>
                >> Â
                >>
                >>
                >>
                >>
                >> On 2010-10-25 11:43 AM, Neil Fleming wrote:
                >>
                >>> * The sources I've read suggest subtracting the bias frame from each dark
                >>> sub-frame before combining them. But couldn't I combine, then subtract just
                >>> once? Or is there a quirk of the algorithm that makes that a bad idea?
                >>
                >> That's a REALLY bad idea. Not because of any quirk, but because MaxIm DL
                >> handles that automatically. Doing it manually will probably result in it being
                >> done TWICE, which would be bad.
                >>
                >> The Set Calibration command is designed to handle everything automatically.
                >> Just dump in all of your calibration frames and let it figure out the details.
                >>
                >> Doug
                >>
                >> --
                >>
                >> Doug George
                >> dgeorge @...
                >>
                >> Diffraction Limited
                >> Makers of Cyanogen Imaging Products
                >> http :// www .cyanogen.com/
                >>
                >> 100 Craig Henry Dr., Suite 202
                >> Ottawa, Ontario,
                >> Canada, K2G 5W3
                >>
                >> Phone: (613) 225-2732
                >> Fax: (613) 225-9688
                >>
                >>
                >>
                >> [Non-text portions of this message have been removed]
                >>
                >
                >
                >
                >
                > ------------------------------------
                >
                >
                >
                >
              • Michael Sherick
                Hello Folks,   It has been a quite a while since I last posted anything to the Groups.  Here is a collection of recent images from my Sagrada Observatory
                Message 7 of 17 , Nov 2, 2010
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                  Hello Folks,
                   
                  It has been a quite a while since I last posted anything to the Groups.  Here is a collection of recent images from my Sagrada Observatory here in Las Cruces, New Mexico.  All data acquired with CCD Commander, imaged with a TMB152 APO and ST10xme, Astrodon GenI filters, external guiding with ST402.
                   
                  Galaxy Images:
                  http://imagingtheheavens.com/?page_id=15
                  The ngc253 image was 70 x 300 sec Luminance, multiple iterations of deconvolution applied.  M33 is an LRGB result.  M81 was 40 x 300 sec Luminance.
                   
                  Nebulae Images (False Color Narrowband):
                  http://imagingtheheavens.com/?page_id=21
                  All these images used 3nm Ha, SII, and OIII filters.
                   
                  Star Cluster Images:
                  http://imagingtheheavens.com/?page_id=24
                  RGB image result.
                   
                  I hope you enjoy the image results. 
                   
                  Clear Skies,
                  Mike Sherick
                   
                   




                  [Non-text portions of this message have been removed]
                • glen youman
                  Excellent images. On the Nebulae images, the nebula you identify as IC 1805 is IC 1795. This can be confirmed with the STScI Digitized Sky Survey, U2000, Seds
                  Message 8 of 17 , Nov 2, 2010
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                    Excellent images.

                    On the Nebulae images, the nebula you identify as IC 1805 is IC 1795.
                    This can be confirmed with the STScI Digitized Sky Survey, U2000, Seds
                    Interactive NGC catalog, etc. IC 1795 is sometimes referred to as the
                    Northern Bear.

                    Clear skies -

                    GYouman

                    On 11/2/2010 3:10 PM, Michael Sherick wrote:
                    > Hello Folks,
                    >
                    > It has been a quite a while since I last posted anything to the Groups. Here is a collection of recent images from my Sagrada Observatory here in Las Cruces, New Mexico. All data acquired with CCD Commander, imaged with a TMB152 APO and ST10xme, Astrodon GenI filters, external guiding with ST402.
                    >
                    > Galaxy Images:
                    > http://imagingtheheavens.com/?page_id=15
                    > The ngc253 image was 70 x 300 sec Luminance, multiple iterations of deconvolution applied. M33 is an LRGB result. M81 was 40 x 300 sec Luminance.
                    >
                    > Nebulae Images (False Color Narrowband):
                    > http://imagingtheheavens.com/?page_id=21
                    > All these images used 3nm Ha, SII, and OIII filters.
                    >
                    > Star Cluster Images:
                    > http://imagingtheheavens.com/?page_id=24
                    > RGB image result.
                    >
                    > I hope you enjoy the image results.
                    >
                    > Clear Skies,
                    > Mike Sherick
                    >
                    >
                    >
                    >
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    >
                    >
                    >
                    >
                  • Michael Sherick
                    Hello Folks,   I added color to the ngc253 data.  Also, I processed M74 in RGB.  Here are the revised results: http://imagingtheheavens.com/?page_id=15  
                    Message 9 of 17 , Nov 3, 2010
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                      Hello Folks,
                       
                      I added color to the ngc253 data.  Also, I processed M74 in RGB.  Here are the revised results:
                      http://imagingtheheavens.com/?page_id=15
                       
                      Clear Skies,
                      Mike
                      ---------------------------------------------------

                      --- On Tue, 11/2/10, Michael Sherick <michaelsherick@...> wrote:


                      From: Michael Sherick <michaelsherick@...>
                      Subject: [ccd-newastro] Recent Image results from Sagrada...
                      To: ccd-newastro@yahoogroups.com
                      Date: Tuesday, November 2, 2010, 3:10 PM


                       



                      Hello Folks,
                       
                      It has been a quite a while since I last posted anything to the Groups.  Here is a collection of recent images from my Sagrada Observatory here in Las Cruces, New Mexico.  All data acquired with CCD Commander, imaged with a TMB152 APO and ST10xme, Astrodon GenI filters, external guiding with ST402.
                       
                      Galaxy Images:
                      http://imagingtheheavens.com/?page_id=15
                      The ngc253 image was 70 x 300 sec Luminance, multiple iterations of deconvolution applied.  M33 is an LRGB result.  M81 was 40 x 300 sec Luminance.
                       
                      Nebulae Images (False Color Narrowband):
                      http://imagingtheheavens.com/?page_id=21
                      All these images used 3nm Ha, SII, and OIII filters.
                       
                      Star Cluster Images:
                      http://imagingtheheavens.com/?page_id=24
                      RGB image result.
                       
                      I hope you enjoy the image results. 
                       
                      Clear Skies,
                      Mike Sherick
                       
                       

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











                      [Non-text portions of this message have been removed]
                    • CurtisC
                      Just speaking about my own experience, M74 has been a very difficult subject. I ve shot it probably eight times in monochrome in the past two years. It seems
                      Message 10 of 17 , Nov 3, 2010
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                        Just speaking about my own experience, M74 has been a very difficult subject. I've shot it probably eight times in monochrome in the past two years. It seems like it should be easy. It's bright, with lots of detail. But there's something about that part of the sky that is brighter than I would expect, with lots of noise that needs to be suppressed. It doesn't help that seeing at this time of year in my area (so.Calif.) is often bad. NGC 772, not far away, has been a piece of cake. I like your picture a lot, Mike. There are some dark spots that look like debris on the camera window or chip that you might want to spot out.

                        --- In ccd-newastro@yahoogroups.com, Michael Sherick <michaelsherick@...> wrote:
                        >
                        > Hello Folks,
                        >  
                        > I added color to the ngc253 data.  Also, I processed M74 in RGB.  Here are the revised results:
                        > http://imagingtheheavens.com/?page_id=15
                        >  
                        > Clear Skies,
                        > Mike
                        > ---------------------------------------------------
                        >
                        > --- On Tue, 11/2/10, Michael Sherick <michaelsherick@...> wrote:
                        >
                        >
                        > From: Michael Sherick <michaelsherick@...>
                        > Subject: [ccd-newastro] Recent Image results from Sagrada...
                        > To: ccd-newastro@yahoogroups.com
                        > Date: Tuesday, November 2, 2010, 3:10 PM
                        >
                        >
                        >  
                        >
                        >
                        >
                        > Hello Folks,
                        >  
                        > It has been a quite a while since I last posted anything to the Groups.  Here is a collection of recent images from my Sagrada Observatory here in Las Cruces, New Mexico.  All data acquired with CCD Commander, imaged with a TMB152 APO and ST10xme, Astrodon GenI filters, external guiding with ST402.
                        >  
                        > Galaxy Images:
                        > http://imagingtheheavens.com/?page_id=15
                        > The ngc253 image was 70 x 300 sec Luminance, multiple iterations of deconvolution applied.  M33 is an LRGB result.  M81 was 40 x 300 sec Luminance.
                        >  
                        > Nebulae Images (False Color Narrowband):
                        > http://imagingtheheavens.com/?page_id=21
                        > All these images used 3nm Ha, SII, and OIII filters.
                        >  
                        > Star Cluster Images:
                        > http://imagingtheheavens.com/?page_id=24
                        > RGB image result.
                        >  
                        > I hope you enjoy the image results. 
                        >  
                        > Clear Skies,
                        > Mike Sherick
                        >  
                        >  
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > [Non-text portions of this message have been removed]
                        >
                      • Bill Snyder
                        Nice Images Mike Bill
                        Message 11 of 17 , Nov 5, 2010
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                          Nice Images Mike
                          Bill

                          --- In ccd-newastro@yahoogroups.com, Michael Sherick <michaelsherick@...> wrote:
                          >
                          > Hello Folks,
                          >  
                          > It has been a quite a while since I last posted anything to the Groups.  Here is a collection of recent images from my Sagrada Observatory here in Las Cruces, New Mexico.  All data acquired with CCD Commander, imaged with a TMB152 APO and ST10xme, Astrodon GenI filters, external guiding with ST402.
                          >  
                          > Galaxy Images:
                          > http://imagingtheheavens.com/?page_id=15
                          > The ngc253 image was 70 x 300 sec Luminance, multiple iterations of deconvolution applied.  M33 is an LRGB result.  M81 was 40 x 300 sec Luminance.
                          >  
                          > Nebulae Images (False Color Narrowband):
                          > http://imagingtheheavens.com/?page_id=21
                          > All these images used 3nm Ha, SII, and OIII filters.
                          >  
                          > Star Cluster Images:
                          > http://imagingtheheavens.com/?page_id=24
                          > RGB image result.
                          >  
                          > I hope you enjoy the image results. 
                          >  
                          > Clear Skies,
                          > Mike Sherick
                          >  
                          >  
                          >
                          >
                          >
                          >
                          > [Non-text portions of this message have been removed]
                          >
                        • Michael Sherick
                          Hello Folks,   Here are a couple of color narrowband images of ic410 and ic405 imaged from my Sagrada Observatory here in Las Cruces, NM.  I hope you enjoy
                          Message 12 of 17 , Nov 16, 2010
                          • 0 Attachment
                            Hello Folks,
                             
                            Here are a couple of color narrowband images of ic410 and ic405 imaged from my Sagrada Observatory here in Las Cruces, NM.  I hope you enjoy the results.
                             
                            http://imagingtheheavens.com/?page_id=21
                             
                            Clear Skies,
                            Mike Sherick
                             
                             




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