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Re: [ccd-newastro] Re: Best Camera to use with new Meade 20" RCX??

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  • Yahoo - Wodaski
    You make a good point - the choices you make ultimately depend on your objectives. By the way, there is a simple (but not cheap!) way to deal with most of
    Message 1 of 16 , Jan 3, 2007
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      You make a good point - the choices you make ultimately depend on your
      objectives.

      By the way, there is a simple (but not cheap!) way to deal with most of
      those seeing fluctuations: build your observatory 10 meters up!

      Ron Wodaski

      Mark de Regt wrote:
      > There is a limiting factor that I'm not sure has been discussed, related to
      > Jason's point. Simply stated, I don't like taking exposures longer than
      > about 30 minutes. In a typical set of data, I will toss a significant
      > portion of the images I take (especially at home; but even from New Mexico,
      > there are images significantly worse that most of them, which get tossed).
      > To some extent, I think that this is a function of transient bad seeing.
      > Heck, spend some time (as I have, and as I'm sure you have) looking at the
      > NMS seeing graph, and you'll see that there are always periods of better and
      > worse seeing, even where you live (not to mention where you used to live
      > <g>). I'd rather toss a few 20 minute images than a few 90 minute images.
      >
      > Also, to the extent that one cares about getting color in stars, the longer
      > you expose, the less color you'll get in fewer stars.
      >
      > As you've noted, it's a complicated situation.
      >
      > --Mark
      >
      >
      >> -----Original Message-----
      >> From: ccd-newastro@yahoogroups.com
      >> [mailto:ccd-newastro@yahoogroups.com]On Behalf Of Yahoo - Wodaski
      >> Sent: Wednesday, January 03, 2007 9:20 AM
      >> To: ccd-newastro@yahoogroups.com
      >> Subject: Re: [ccd-newastro] Re: Best Camera to use with new Meade 20"
      >> RCX??
      >>
      >>
      >> Still, you have to do the math to see if those additional sub-frames are
      >> going to help you enough. If the read noise is high enough, even a lot
      >> of additional sub-frames may not be enough to overcome the read noise.
      >>
      >> The greater the read noise contribution, the slower the rate at which
      >> additional sub-frames improve your overall S/N using combining. I have
      >> created some graphs to compare (sorry, none of this available anywhere
      >> on the net yet), and you would be quite surprised at how much read noise
      >> affects the rate of improvement as read noise increases. Worse, the rate
      >> of improvement tends to get quite flat at some point as you increase the
      >> number of sub-frames while holding noise constant.
      >>
      >> I've used both cameras on my 20" RC, and no question I can go deeper
      >> with less hassle and less time using the lower QE camera due to the
      >> non-QE factors involved.
      >>
      >> And that's my point. Don't assume that a higher QE automatically gives
      >> you more efficiency under all conditions. Take everything that
      >> contributes to both signal and noise into account in order to know how
      >> deep you can go.
      >>
      >> I've said this many times: signal to noise is NOT intuitive. You can't
      >> apply our everyday experience to know what to expect in the realm of
      >> noise effects. In the end, the only way to know what happens (or to
      >> explain when odd things happen) is to do the math.
      >>
      >> Ron Wodaski
      >>
      >> galaxy_jason wrote:
      >>
      >>> --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...>
      >>> wrote:
      >>>
      >>>
      >>>> With the 6303, however, in many (if not most) cases, you
      >>>> are going to cut the exposure time down to avoid excessive blooming.
      >>>>
      >>>>
      >>> But you can take many more subframes!
      >>>
      >>> -Jason Ware
      >>> galaxyphoto.com
      >>>
      >>>
      >>>
      >>> Yahoo! Groups Links
      >>>
      >>>
      >>>
      >>>
      >>>
      >> Yahoo! Groups Links
      >>
      >>
      >>
      >>
      >
      >
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
    • Mark de Regt
      I ll ask Mike to raise our dome a mere 10 meters. I m sure our neighbors (particularly Rob) won t mind giving up a bit of their sky for our benefit. Your
      Message 2 of 16 , Jan 3, 2007
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        I'll ask Mike to raise our dome a mere 10 meters. I'm sure our neighbors
        (particularly Rob) won't mind giving up a bit of their sky for our benefit.
        <g>

        Your dome isn't 10 meters up, but it is raised. Does that help?

        > -----Original Message-----
        > From: ccd-newastro@yahoogroups.com
        > [mailto:ccd-newastro@yahoogroups.com]On Behalf Of Yahoo - Wodaski
        > Sent: Wednesday, January 03, 2007 10:42 AM
        > To: ccd-newastro@yahoogroups.com
        > Subject: Re: [ccd-newastro] Re: Best Camera to use with new Meade 20"
        > RCX??
        >
        >
        > You make a good point - the choices you make ultimately depend on your
        > objectives.
        >
        > By the way, there is a simple (but not cheap!) way to deal with most of
        > those seeing fluctuations: build your observatory 10 meters up!
        >
        > Ron Wodaski
        >
        > Mark de Regt wrote:
        > > There is a limiting factor that I'm not sure has been
        > discussed, related to
        > > Jason's point. Simply stated, I don't like taking exposures longer than
        > > about 30 minutes. In a typical set of data, I will toss a significant
        > > portion of the images I take (especially at home; but even from
        > New Mexico,
        > > there are images significantly worse that most of them, which
        > get tossed).
        > > To some extent, I think that this is a function of transient bad seeing.
        > > Heck, spend some time (as I have, and as I'm sure you have)
        > looking at the
        > > NMS seeing graph, and you'll see that there are always periods
        > of better and
        > > worse seeing, even where you live (not to mention where you used to live
        > > <g>). I'd rather toss a few 20 minute images than a few 90
        > minute images.
        > >
        > > Also, to the extent that one cares about getting color in
        > stars, the longer
        > > you expose, the less color you'll get in fewer stars.
        > >
        > > As you've noted, it's a complicated situation.
        > >
        > > --Mark
        > >
        > >
        > >> -----Original Message-----
        > >> From: ccd-newastro@yahoogroups.com
        > >> [mailto:ccd-newastro@yahoogroups.com]On Behalf Of Yahoo - Wodaski
        > >> Sent: Wednesday, January 03, 2007 9:20 AM
        > >> To: ccd-newastro@yahoogroups.com
        > >> Subject: Re: [ccd-newastro] Re: Best Camera to use with new Meade 20"
        > >> RCX??
        > >>
        > >>
        > >> Still, you have to do the math to see if those additional
        > sub-frames are
        > >> going to help you enough. If the read noise is high enough, even a lot
        > >> of additional sub-frames may not be enough to overcome the read noise.
        > >>
        > >> The greater the read noise contribution, the slower the rate at which
        > >> additional sub-frames improve your overall S/N using combining. I have
        > >> created some graphs to compare (sorry, none of this available anywhere
        > >> on the net yet), and you would be quite surprised at how much
        > read noise
        > >> affects the rate of improvement as read noise increases.
        > Worse, the rate
        > >> of improvement tends to get quite flat at some point as you
        > increase the
        > >> number of sub-frames while holding noise constant.
        > >>
        > >> I've used both cameras on my 20" RC, and no question I can go deeper
        > >> with less hassle and less time using the lower QE camera due to the
        > >> non-QE factors involved.
        > >>
        > >> And that's my point. Don't assume that a higher QE automatically gives
        > >> you more efficiency under all conditions. Take everything that
        > >> contributes to both signal and noise into account in order to know how
        > >> deep you can go.
        > >>
        > >> I've said this many times: signal to noise is NOT intuitive. You can't
        > >> apply our everyday experience to know what to expect in the realm of
        > >> noise effects. In the end, the only way to know what happens (or to
        > >> explain when odd things happen) is to do the math.
        > >>
        > >> Ron Wodaski
        > >>
        > >> galaxy_jason wrote:
        > >>
        > >>> --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...>
        > >>> wrote:
        > >>>
        > >>>
        > >>>> With the 6303, however, in many (if not most) cases, you
        > >>>> are going to cut the exposure time down to avoid excessive blooming.
        > >>>>
        > >>>>
        > >>> But you can take many more subframes!
        > >>>
        > >>> -Jason Ware
        > >>> galaxyphoto.com
        > >>>
        > >>>
        > >>>
        > >>> Yahoo! Groups Links
        > >>>
        > >>>
        > >>>
        > >>>
        > >>>
        > >> Yahoo! Groups Links
        > >>
        > >>
        > >>
        > >>
        > >
        > >
        > >
        > > Yahoo! Groups Links
        > >
        > >
        > >
        > >
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
      • Yahoo - Wodaski
        Mine is raised, but is surrounded by trees and building. So not a big benefit. But Chris Traher s/Randy Nulman s dome is up about 7 meters (across the valley
        Message 3 of 16 , Jan 3, 2007
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          Mine is raised, but is surrounded by trees and building. So not a big
          benefit. But Chris Traher's/Randy Nulman's dome is up about 7 meters
          (across the valley from you), and with proper heat and airflow
          management, we can better the ground-level seeing by half an arcsecond,
          sometimes a little more.

          Ron Wodaski

          Mark de Regt wrote:
          > I'll ask Mike to raise our dome a mere 10 meters. I'm sure our neighbors
          > (particularly Rob) won't mind giving up a bit of their sky for our benefit.
          > <g>
          >
          > Your dome isn't 10 meters up, but it is raised. Does that help?
          >
          >
          >> -----Original Message-----
          >> From: ccd-newastro@yahoogroups.com
          >> [mailto:ccd-newastro@yahoogroups.com]On Behalf Of Yahoo - Wodaski
          >> Sent: Wednesday, January 03, 2007 10:42 AM
          >> To: ccd-newastro@yahoogroups.com
          >> Subject: Re: [ccd-newastro] Re: Best Camera to use with new Meade 20"
          >> RCX??
          >>
          >>
          >> You make a good point - the choices you make ultimately depend on your
          >> objectives.
          >>
          >> By the way, there is a simple (but not cheap!) way to deal with most of
          >> those seeing fluctuations: build your observatory 10 meters up!
          >>
          >> Ron Wodaski
          >>
          >> Mark de Regt wrote:
          >>
          >>> There is a limiting factor that I'm not sure has been
          >>>
          >> discussed, related to
          >>
          >>> Jason's point. Simply stated, I don't like taking exposures longer than
          >>> about 30 minutes. In a typical set of data, I will toss a significant
          >>> portion of the images I take (especially at home; but even from
          >>>
          >> New Mexico,
          >>
          >>> there are images significantly worse that most of them, which
          >>>
          >> get tossed).
          >>
          >>> To some extent, I think that this is a function of transient bad seeing.
          >>> Heck, spend some time (as I have, and as I'm sure you have)
          >>>
          >> looking at the
          >>
          >>> NMS seeing graph, and you'll see that there are always periods
          >>>
          >> of better and
          >>
          >>> worse seeing, even where you live (not to mention where you used to live
          >>> <g>). I'd rather toss a few 20 minute images than a few 90
          >>>
          >> minute images.
          >>
          >>> Also, to the extent that one cares about getting color in
          >>>
          >> stars, the longer
          >>
          >>> you expose, the less color you'll get in fewer stars.
          >>>
          >>> As you've noted, it's a complicated situation.
          >>>
          >>> --Mark
          >>>
          >>>
          >>>
          >>>> -----Original Message-----
          >>>> From: ccd-newastro@yahoogroups.com
          >>>> [mailto:ccd-newastro@yahoogroups.com]On Behalf Of Yahoo - Wodaski
          >>>> Sent: Wednesday, January 03, 2007 9:20 AM
          >>>> To: ccd-newastro@yahoogroups.com
          >>>> Subject: Re: [ccd-newastro] Re: Best Camera to use with new Meade 20"
          >>>> RCX??
          >>>>
          >>>>
          >>>> Still, you have to do the math to see if those additional
          >>>>
          >> sub-frames are
          >>
          >>>> going to help you enough. If the read noise is high enough, even a lot
          >>>> of additional sub-frames may not be enough to overcome the read noise.
          >>>>
          >>>> The greater the read noise contribution, the slower the rate at which
          >>>> additional sub-frames improve your overall S/N using combining. I have
          >>>> created some graphs to compare (sorry, none of this available anywhere
          >>>> on the net yet), and you would be quite surprised at how much
          >>>>
          >> read noise
          >>
          >>>> affects the rate of improvement as read noise increases.
          >>>>
          >> Worse, the rate
          >>
          >>>> of improvement tends to get quite flat at some point as you
          >>>>
          >> increase the
          >>
          >>>> number of sub-frames while holding noise constant.
          >>>>
          >>>> I've used both cameras on my 20" RC, and no question I can go deeper
          >>>> with less hassle and less time using the lower QE camera due to the
          >>>> non-QE factors involved.
          >>>>
          >>>> And that's my point. Don't assume that a higher QE automatically gives
          >>>> you more efficiency under all conditions. Take everything that
          >>>> contributes to both signal and noise into account in order to know how
          >>>> deep you can go.
          >>>>
          >>>> I've said this many times: signal to noise is NOT intuitive. You can't
          >>>> apply our everyday experience to know what to expect in the realm of
          >>>> noise effects. In the end, the only way to know what happens (or to
          >>>> explain when odd things happen) is to do the math.
          >>>>
          >>>> Ron Wodaski
          >>>>
          >>>> galaxy_jason wrote:
          >>>>
          >>>>
          >>>>> --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...>
          >>>>> wrote:
          >>>>>
          >>>>>
          >>>>>
          >>>>>> With the 6303, however, in many (if not most) cases, you
          >>>>>> are going to cut the exposure time down to avoid excessive blooming.
          >>>>>>
          >>>>>>
          >>>>>>
          >>>>> But you can take many more subframes!
          >>>>>
          >>>>> -Jason Ware
          >>>>> galaxyphoto.com
          >>>>>
          >>>>>
          >>>>>
          >>>>> Yahoo! Groups Links
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>>>
          >>>> Yahoo! Groups Links
          >>>>
          >>>>
          >>>>
          >>>>
          >>>>
          >>>
          >>> Yahoo! Groups Links
          >>>
          >>>
          >>>
          >>>
          >>>
          >> Yahoo! Groups Links
          >>
          >>
          >>
          >>
          >
          >
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
        • howsoft_paul
          I don t understand the reasoning here. Are you talking about luminance washing out the RGB? Or just doing longer RGB results in washed out color in the
          Message 4 of 16 , Jan 3, 2007
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            I don't understand the reasoning here. Are you talking about
            luminance washing out the RGB? Or just doing longer RGB results in
            washed out color in the stars?

            Thanx,

            Paul Howard

            >
            > Also, to the extent that one cares about getting color in stars, the
            longer
            > you expose, the less color you'll get in fewer stars.
            >
          • Mark de Regt
            Paul, The longer you expose, the more pixels in stars will be saturated. Saturated stars in the luminance layer aren t friendly to color coming through from
            Message 5 of 16 , Jan 3, 2007
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              Paul,

              The longer you expose, the more pixels in stars will be saturated.
              Saturated stars in the luminance layer aren't friendly to color coming
              through from the RGB layer. So if you have a lot of saturated stars, you
              will have a lot of white stars. That's not bad; just not what some people
              want.

              --Mark

              > -----Original Message-----
              > From: ccd-newastro@yahoogroups.com
              > [mailto:ccd-newastro@yahoogroups.com]On Behalf Of howsoft_paul
              > Sent: Wednesday, January 03, 2007 9:16 PM
              > To: ccd-newastro@yahoogroups.com
              > Subject: [ccd-newastro] Re: Best Camera to use with new Meade 20" RCX??
              >
              >
              > I don't understand the reasoning here. Are you talking about
              > luminance washing out the RGB? Or just doing longer RGB results in
              > washed out color in the stars?
              >
              > Thanx,
              >
              > Paul Howard
              >
              > >
              > > Also, to the extent that one cares about getting color in stars, the
              > longer
              > > you expose, the less color you'll get in fewer stars.
              > >
              >
              >
              >
              >
              > Yahoo! Groups Links
              >
              >
              >
            • drgert1
              Hi, I highly recommend Ron s deblooming software. The best I ve seen so far. I am using a KAF (blooming) chip and other than attempting 10min subs of M42 with
              Message 6 of 16 , Jan 4, 2007
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                Hi,

                I highly recommend Ron's deblooming software. The best I've seen so
                far. I am using a KAF (blooming) chip and other than attempting 10min
                subs of M42 with the trapezium in the field I've been very happy with
                Ron's product.

                Thanks to Ron! & Clear Skies,

                Gert

                --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...> wrote:
                >
                > Here's an interesting twist on the STL-11000/STL-6303 efficiency.
                >
                > Under dark skies, it's actually possible for the STL-11000 to go
                > _deeper_ than the 6303 if your goal is pretty pictures. Yes, you read
                > that right. Before you panic, read on.
                >
                > Keep in mind that the goal is _always_ to get the best possible signal
                > to noise ratio. One does this by taking long enough individual
                exposures
                > to minimize the read noise with respect to the shot noise (a large
                > subject that I am not going to deal with here).
                >
                > Under dark skies, one needs to take long individual exposures to
                achieve
                > this goal. for the STL-11000, you are free to take really long
                > individual exposures because it is an anti-blooming camera. (Because of
                > dark skies, it would take you maybe an hour and a half to minimize the
                > read noise.) With the 6303, however, in many (if not most) cases, you
                > are going to cut the exposure time down to avoid excessive blooming. So
                > the read noise might (and often will) be greater by a significant
                amount
                > compared to the read noise contribution in the long STL011k image.
                >
                > So you think to yourself - I will take a larger number of these shorter
                > exposures and combine them to drive down the read noise contribution. A
                > good approach - but it only is useful if your individual exposure times
                > are long enough to give you a reasonably small read noise
                contribution.
                > Due to cutting the exposure time short to avoid blooming, however, one
                > can easily allow a surprisingly large read noise component, and even
                > dozens of individual images will still have surprisingly large read
                noise.
                >
                > So you may have to allow significantly more radical blooming than you
                > would like in order to get low enough read noise to go deep with an
                > STL-6303 under dark skies!
                >
                > And of course you have to spend the time cleaning them up by whatever
                > means (and that time will be longer for more extreme blooms...)
                >
                > So you can, under the right conditions, save yourself some time by
                > getting a camera with lower QE!
                >
                > For the record, you need really dark skies (such as we enjoy in the
                > rural New Mexico mountains) in order to be "plagued" by this problem.
                > <G> But ti does demonstrate that it's not a slam dunk to assume that a
                > higher QE camera is really more efficient; you have to take all
                > contributions to S/N into account to know what will be most efficient
                > overall.
                >
                > Ron Wodaski
                >
                > Mark de Regt wrote:
                > > Assuming you want to make pretty pictures, I suspect that you
                could use any
                > > camera you wanted. Sky & Telescope found that a 12" RCX400
                illuminated a
                > > full-frame CCD without coma, so there's no reason why a 20"
                wouldn't do as
                > > well, I think.
                > >
                > > If I were spending that much on scope and mount, I would be
                getting an SBIG
                > > STL11000 (or perhaps an STL6303 for its higher efficiency).
                > >
                > > --Mark
                > >
                > >
                > >> -----Original Message-----
                > >> From: ccd-newastro@yahoogroups.com
                > >> [mailto:ccd-newastro@yahoogroups.com]On Behalf Of John
                > >> Sent: Saturday, December 30, 2006 4:45 PM
                > >> To: ccd-newastro@yahoogroups.com
                > >> Subject: [ccd-newastro] Best Camera to use with new Meade 20" RCX??
                > >>
                > >>
                > >> Hi group,
                > >> Looking for suggestions.
                > >> Thanks
                > >> John
                > >>
                > >>
                > >>
                > >> Yahoo! Groups Links
                > >>
                > >>
                > >>
                > >>
                > >
                > >
                > >
                > > Yahoo! Groups Links
                > >
                > >
                > >
                > >
                >
              • howsoft_paul
                Mark, Thanx, Paul
                Message 7 of 16 , Jan 4, 2007
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                  Mark,

                  Thanx,

                  Paul
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