Optimal Exposure and Noise Calculator

[joseph.mcgee at sbcglobal.net]

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 at 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 at 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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