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List: kstars-devel
Subject: Re: Optimal Exposure and Noise Calculator
From: "joseph.mcgee () sbcglobal ! net" <joseph ! mcgee () sbcglobal ! net>
Date: 2023-03-05 18:52:57
Message-ID: 1452914e-fb69-9187-3d36-0769d5e9942b () sbcglobal ! net
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Thanks Warren,
I will review the link and try again. Stay safe in Tahoe, it looks like
another big storm in approaching.
On 3/5/23 08:50, Warren wrote:
> Hey Joseph, you may inadvertently be getting some light into your bias
> frames. Make sure you cap the camera like you’d do for dark frames.
>
> Here’s a more explicit, complete process for measuring read noise from
> bias images. I don’t have access to an astro camera at the moment (I’m
> snowed in at Lake Tahoe, boo hoo) to verify this process, but I can
> try it myself in a couple days.
>
> http://astro.physics.uiowa.edu/~kaaret/2013f_29c137/Lab03_noise.html#:~:text=The%20read%20noise%20of%20the,removing%20hot%20and%20dead%20pixels).
>
> In regards to subexposure length, I’m not personally against the
> calculator, but maybe it should have a disclaimer. I think it’s true
> that almost everyone using recent CMOS cameras should just use, say,
> two minutes by default. This consistency really simplifies workflow.
>
> If you have trouble with tracking, periodic error, tracking, fast high
> clouds, wind gusts, polar alignment, etc. then you can switch to 30-
> or 60-second subs with almost no effect other than using more disk
> space and more CPU time.
>
> There may be people using older CCD cameras with KStars / Ekos though!
>
> - W
>
> On Sat, Mar 4, 2023 at 10:38 PM Wolfgang Reissenberger
> <sterne-jaeger@openfuture.de> wrote:
>
> Joseph,
> I’m not sure what type of function we are talking here. Is your
> intention to calculate the optimal exposure time for a single
> frame or for the target? If its the first one, I have the same
> questions as Hy. For the latter, I’m happy to learn more about it.
>
> Wolfgang
> —
> Wolfgang Reissenberger
>
> www.sterne-jaeger.de <http://www.sterne-jaeger.de>
> TSA-120 + FSQ-85 + epsilon-160 | Avalon Linear + M-zero | ASI
> 1600mm pro + 6200mm pro
>
> > Am 05.03.2023 um 06:06 schrieb joseph.mcgee@sbcglobal.net:
> >
> > Hi All,
> >
> > Let me explain my reasoning for developing the optimal exposure
> > calculator and noise calculator. I started fairly recently in
> > this A.P. hobby (mid 2019), and had no mentor. Most of the online
> > resources seemed to provide information and suggestions that were
> > geared toward imaging in very dark skies with more advanced
> > equipment than a beginner would own. The typical recommended
> > exposure times I read about were on the order of a many minutes.
> >
> > But when I was experimenting with and learning to use my gear, I
> > typically did so in my own backyard (SQM 19.63). I initially
> > spent quite a few frustrating nights trying to find exposure
> > settings that would produce a decent image. As I acquired
> > filters, I had to repeat the learning process. Then when I had
> > the opportunity to travel to a darker site 90 miles from my home,
> > (SQM 21.65), I again had to repeat the learning process. The
> > difference in the exposure times at these two sites was pretty
> > shocking to me.
> >
> > I fully grasp that you all have considerable experience with A.P.
> > but this tool is really not intended to provide benefit to folks
> > that have such experience. The target audience for this tool is
> > the newcomer to this hobby (like me three years ago). I would
> > have been thrilled to have tool that says when I'm in my backyard
> > shooting with gain at 100, and no filter, that my exposure time
> > should only be around 45 seconds.
> >
> > Now, back to the topic...
> >
> > Warren,
> >
> > You raised a suggestion that bias frames could be used to
> > determine sensor read noise. I must be missing some knowledge in
> > this area. I just ran a test with my planetary camera (ASI-178),
> > where I captured a set of bias frames incrementing the gain from
> > 0 to 400 in steps of 50, with an exposure time 32us, (I believe
> > that is the lower limit for the ASI-178). I then used a tool
> > that can assess noise in the image. The noise measured in each
> > image increased as the gain increased; so this did not match the
> > downward trend I expected from the ZWO read-noise graph.
> >
> > Perhaps the tool I used for noise assessment was not the best choice.
> >
> > Can you explain further how I might be able to analyze bias
> > frames to determine read noise?
> >
> > Thanks
> >
> >
> >
>
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<p>Thanks Warren, <br>
</p>
<p>I will review the link and try again. Stay safe in Tahoe, it
looks like another big storm in approaching.<br>
</p>
<div class="moz-cite-prefix">On 3/5/23 08:50, Warren wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CALeJgM804ozPW6=4GwCMVxtAOu5GaEJ0g9opk9LL2YPRegcMdw@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="auto">Hey Joseph, you may inadvertently be getting some
light into your bias frames. Make sure you cap the camera like
you'd do for dark frames.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Here's a more explicit, complete process for
measuring read noise from bias images. I don't have access to an
astro camera at the moment (I'm snowed in at Lake Tahoe, boo
hoo) to verify this process, but I can try it myself in a couple
days.</div>
<div dir="auto"><br>
</div>
<div dir="auto">
<div><a
href="http://astro.physics.uiowa.edu/~kaaret/2013f_29c137/Lab03_noise.html#:~:text=The%20read%20noise%20of%20the,removing%20hot%20and%20dead%20pixels"
moz-do-not-send="true" \
class="moz-txt-link-freetext">http://astro.physics.uiowa.edu/~kaaret/2013f_29c137/Lab0 \
3_noise.html#:~:text=The%20read%20noise%20of%20the,removing%20hot%20and%20dead%20pixels</a>).</div>
<br>
</div>
<div dir="auto">In regards to subexposure length, I'm not
personally against the calculator, but maybe it should have a
disclaimer. I think it's true that almost everyone using recent
CMOS cameras should just use, say, two minutes by default. This
consistency really simplifies workflow.</div>
<div dir="auto"><br>
</div>
<div dir="auto">If you have trouble with tracking, periodic error,
tracking, fast high clouds, wind gusts, polar alignment, etc.
then you can switch to 30- or 60-second subs with almost no
effect other than using more disk space and more CPU time.</div>
<div dir="auto"><br>
</div>
<div dir="auto">There may be people using older CCD cameras with
KStars / Ekos though!</div>
<div dir="auto"><br>
</div>
<div dir="auto">- W</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Mar 4, 2023 at 10:38
PM Wolfgang Reissenberger <<a
href="mailto:sterne-jaeger@openfuture.de"
moz-do-not-send="true" \
class="moz-txt-link-freetext">sterne-jaeger@openfuture.de</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div style="line-break:after-white-space">Joseph,
<div>I'm not sure what type of function we are talking
here. Is your intention to calculate the optimal
exposure time for a single frame or for the target? If
its the first one, I have the same questions as Hy. For
the latter, I'm happy to learn more about it.</div>
<div><br>
</div>
<div>Wolfgang<br>
<div>
<div dir="auto"
style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;whit \
e-space:normal;word-spacing:0px;text-decoration:none;line-break:after-white-space;color:rgb(0,0,0)">
<div dir="auto"
style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;whit \
e-space:normal;word-spacing:0px;text-decoration:none;line-break:after-white-space;color:rgb(0,0,0)">
<div dir="auto"
style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;whit \
e-space:normal;word-spacing:0px;text-decoration:none;line-break:after-white-space;color:rgb(0,0,0)">
<div dir="auto"
style="line-break:after-white-space">
<div
style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal \
;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transf \
orm:none;white-space:normal;word-spacing:0px;text-decoration:none;color:rgb(0,0,0)">â</div>
<div
style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal \
;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transf \
orm:none;white-space:normal;word-spacing:0px;text-decoration:none;color:rgb(0,0,0)">Wolfgang
Reissenberger<br>
<br>
</div>
<div
style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal \
;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transf \
orm:none;white-space:normal;word-spacing:0px;text-decoration:none;color:rgb(0,0,0)"><a
href="http://www.sterne-jaeger.de"
target="_blank"
style="font-family:Helvetica"
moz-do-not-send="true">www.sterne-jaeger.de</a><br>
TSA-120 + FSQ-85 + epsilon-160 | Avalon
Linear + M-zero | ASI 1600mm pro + 6200mm
pro</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<div style="line-break:after-white-space">
<div>
<div><br>
<blockquote type="cite">
<div>Am 05.03.2023 um 06:06 schrieb <a
href="mailto:joseph.mcgee@sbcglobal.net"
target="_blank" moz-do-not-send="true"
\
class="moz-txt-link-freetext">joseph.mcgee@sbcglobal.net</a>:</div> <br>
<div>
<div>Hi All,<br>
<br>
Let me explain my reasoning for developing the
optimal exposure calculator and noise
calculator. I started fairly recently in this
A.P. hobby (mid 2019), and had no mentor. Most
of the online resources seemed to provide
information and suggestions that were geared
toward imaging in very dark skies with more
advanced equipment than a beginner would own.
The typical recommended exposure times I read
about were on the order of a many minutes.<br>
<br>
But when I was experimenting with and learning
to use my gear, I typically did so in my own
backyard (SQM 19.63). I initially spent quite a
few frustrating nights trying to find exposure
settings that would produce a decent image. As
I acquired filters, I had to repeat the learning
process. Then when I had the opportunity to
travel to a darker site 90 miles from my home,
(SQM 21.65), I again had to repeat the learning
process. The difference in the exposure times
at these two sites was pretty shocking to me.<br>
<br>
I fully grasp that you all have considerable
experience with A.P. but this tool is really not
intended to provide benefit to folks that have
such experience. The target audience for this
tool is the newcomer to this hobby (like me
three years ago). I would have been thrilled to
have tool that says when I'm in my backyard
shooting with gain at 100, and no filter, that
my exposure time should only be around 45
seconds.<br>
<br>
Now, back to the topic...<br>
<br>
Warren,<br>
<br>
You raised a suggestion that bias frames could
be used to determine sensor read noise. I must
be missing some knowledge in this area. I just
ran a test with my planetary camera (ASI-178),
where I captured a set of bias frames
incrementing the gain from 0 to 400 in steps of
50, with an exposure time 32us, (I believe that
is the lower limit for the ASI-178). I then
used a tool that can assess noise in the image.
The noise measured in each image increased as
the gain increased; so this did not match the
downward trend I expected from the ZWO
read-noise graph.<br>
<br>
Perhaps the tool I used for noise assessment was
not the best choice.<br>
<br>
Can you explain further how I might be able to
analyze bias frames to determine read noise?<br>
<br>
Thanks<br>
<br>
<br>
<br>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</div>
</blockquote>
</div>
</div>
</blockquote>
</body>
</html>
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