Optimal Exposure and Noise Calculator

Sat Mar 4 20:31:42 GMT 2023

Hey, Hy!! Long time, no see!

I agree with you, most people would be better off just sticking to a single
reasonable sub length, often 2-4 minutes. It eliminates the complexity of a
dark library, etc.

See Lee Pullen’s Point 4 here:
https://urbanastrophotography.com/index.php/2021/06/14/how-to-get-long-integration-times/

On Sat, Mar 4, 2023 at 11:53 AM Joseph McGee <joseph.mcgee at sbcglobal.net>
wrote:

> Oh, that's very interesting.  We could potentially build a noise profile
> for any camera.
>
> But need to learn how to translate data from a bias frame into a value.
>
> On Mar 4, 2023 at 11:19 AM, Warren <warren.craddock at gmail.com> wrote:
>
> Hey all, I believe you can directly measure read noise from a series of
> bias frames, which are taken at the shortest possible exposure duration.
> That eliminates dark current and photon shot noise, leaving only the read
> noise.
>
> I don’t think it’s necessary to make a database of popular cameras. :)
>
> On Sat, Mar 4, 2023 at 10:16 AM joseph.mcgee at sbcglobal.net <
> joseph.mcgee at sbcglobal.net> wrote:
>
>> Hi Jasem,
>>
>> I don't believe that we would be able to measure (or distinguish) the
>> read noise from an image. My understanding of read noise is that it is
>> introduced during the process where the analog to digital converter is
>> reading the pixel values on the sensor when the exposure is completed and
>> the data is being prepared in a buffer for transmission over the USB
>> connection.
>>
>> I'd used a graph from the ZWO website for the gain to read noise values
>> on my camera.  But I just looked at the QHY website and see some similar
>> graphs. The QHY graph is actually more detailed than what I've seen on ZWO
>> site.
>>
>> So it would be a bit tedious to transcribe these values from the graphs
>> for every possible camera.  Maybe I can contact ZWO and QHY to see if they
>> will provide raw data for their cameras.
>>
>>
>> On 3/4/23 09:19, Jasem Mutlaq wrote:
>>
>> Hello Joseph,
>>
>> You can use QtCreator which is easier for UI Qt designs. But you can use
>> any IDE you feel comfortable with. Is the sensor gain to read noise ratio
>> something that can be measured from FITS Viewer by perhaps capturing a few
>> imagers with different gains + exposure values?
>>
>> --
>> Best Regards,
>> Jasem Mutlaq
>>
>>
>>
>> On Sat, Mar 4, 2023 at 8:01 PM joseph.mcgee at sbcglobal.net <
>> joseph.mcgee at sbcglobal.net> wrote:
>>
>>> Thank you Jasem,
>>>
>>> I have not yet setup a dev environment for KStars; I normally use
>>> Eclipse, but I will install one of the recommended IDEs. For most of the
>>> last 20 years of my career I was developing middle tier code, no recent
>>> user interface work. So I'll need to ramp back up on UI development.  A few
>>> folks have offered to mentor me on integrating this into KStars.  So I'll
>>> get rolling on this shortly.
>>>
>>> I did not realize that I could get SQM from Indi/Ekos, that solves a big
>>> concern for me!
>>>
>>> There is another dependency for the calculation. My code has a small
>>> reference table that relates the imaging sensor gain value to a sensor read
>>> noise value. I've only built one table so far; for my ZWO ASI-071. So I'll
>>> need to work on building tables for other cameras, (but it might be better
>>> if I built a curve-fitted functions for this because the tables limit the
>>> gain selection to specific values).
>>>
>>> Would you happen to have list of the most commonly used cameras?
>>>
>>>
>>>
>>> On 3/4/23 00:12, Jasem Mutlaq wrote:
>>>
>>> Hello Joseph,
>>>
>>> This would be an *outstanding* feature to add to KStars! Thank you for
>>> working on it. It would require an interface and also proper
>>> integration with the rest of KStars & INDI infrastructure, for example, the
>>> filters used..etc.
>>>
>>> Would this be better suited for FITS Viewer integration?
>>>
>>> SQM & F-Ratios can be retrieved from INDI/Ekos, we probably need to add
>>> a field for the filter band-pass in the equipment manager.
>>>
>>> Do you have a development environment ready as per the instructions in
>>> KStars Gitlab? https://invent.kde.org/education/kstars
>>>
>>> --
>>> Best Regards,
>>> Jasem Mutlaq
>>>
>>>
>>>
>>> On Fri, Mar 3, 2023 at 8:16 PM joseph.mcgee at sbcglobal.net <
>>> joseph.mcgee at sbcglobal.net> wrote:
>>>
>>>> Hi All,
>>>>
>>>> I'm a retired software developer (mostly Java, C, and some C++).  I've
>>>> been using KStars on a Raspberry Pi (Ubuntu), since I got interested in AP,
>>>> (around 2020).  Back in late 2021 I wrote an optimal exposure time
>>>> calculator (in Java), based on the work of Dr Glover.  I just got to
>>>> thinking that it might be a nice addition to KStars, and today I found a
>>>> request for it:
>>>> https://indilib.org/forum/wish-list/5300-exposure-calulator.html?start=12
>>>>
>>>> My current code is pretty simple but has no user interface.  It uses a
>>>> few classes for configuration, a table of sensor gain to read noise,
>>>> observation site location SQM value, optics F ratio data, and
>>>> (experimentally) a filter bandpass table.  The code just iterates through
>>>> all the combinations of the inputs to output tab delimited data to the
>>>> console, that I copy into a spreadsheet.
>>>>
>>>> Keep in mind that the exposure time calculations are optimal (per Dr
>>>> Glover), but not necessarily practical.  I've seen a slow optic, with a
>>>> filter, in very dark skies,  produce a optimal sub exposure time
>>>> calculation that exceeded 3 hours.
>>>>
>>>> If this were integrated into KStars, we would obviously need to provide
>>>> a means for a user to input some of their own configuration information.
>>>>
>>>> Please let me know if you'd like to consider integrating this into
>>>> KStars, (I would need coaching/help if I were to take this on).
>>>>
>>>> Example output:
>>>>
>>>> I have my code configured for the read noise for my main imaging
>>>> camera, (a ZWO ASI-071 Color), SQM data for four observation sites.  F
>>>> ratios for four optics, and bandpass info for two filters.  And I'm using
>>>> an allowable noise increase of 5%.
>>>>
>>>> A small section of the output provides this information for a given
>>>> site, optic, and sensor gain selection:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *Site Name:*
>>>>
>>>> Chuchupate
>>>>
>>>>
>>>> *Sky Quality:*
>>>>
>>>> 21.65
>>>>
>>>> magnitude per arc-second2
>>>>
>>>> *Light Pollution Base Rate:*
>>>>
>>>> 19.6
>>>>
>>>> e per second
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *Optic Name:*
>>>>
>>>> Esprit 100
>>>>
>>>>
>>>> *Light Pollution Rate:*
>>>>
>>>> 0.65
>>>>
>>>> e per second for f/5.5 optic
>>>>
>>>>
>>>>
>>>> *Camera Sensor Gain:*
>>>>
>>>> 50
>>>>
>>>> *Read Noise:*
>>>>
>>>> 2.78
>>>>
>>>>
>>>>
>>>> *Filter*
>>>>
>>>> *Optimal Sub-exposure (sec)*
>>>>
>>>> *Shot pollution electrons*
>>>>
>>>> *Exposure shot noise*
>>>>
>>>> *Exposure total noise*
>>>>
>>>> No Filter
>>>>
>>>> 349.1
>>>>
>>>> 226.2
>>>>
>>>> 15
>>>>
>>>> 15.3
>>>>
>>>> Optolong l-Pro
>>>>
>>>> 634.8
>>>>
>>>> 411.3
>>>>
>>>> 20.3
>>>>
>>>> 20.5
>>>>
>>>> Optolong l-Enhance
>>>>
>>>> 3174
>>>>
>>>> 2056.3
>>>>
>>>> 45.3
>>>>
>>>> 45.4
>>>>
>>>> And accumulated data for imaging sessions of 1 to 5 hours:
>>>>
>>>>
>>>>
>>>> *3,600.00 seconds*
>>>>
>>>> *7,200.00 seconds*
>>>>
>>>> *10,800.00 seconds*
>>>>
>>>> *14,400.00 seconds*
>>>>
>>>> *18,000.00 seconds*
>>>>
>>>> *Filter*
>>>>
>>>> *Exposure Count*
>>>>
>>>> *Stack Total Time*
>>>>
>>>> *Stack total noise*
>>>>
>>>> *Exposure Count*
>>>>
>>>> *Stack Total Time*
>>>>
>>>> *Stack total noise*
>>>>
>>>> *Exposure Count*
>>>>
>>>> *Stack Total Time*
>>>>
>>>> *Stack total noise*
>>>>
>>>> *Exposure Count*
>>>>
>>>> *Stack Total Time*
>>>>
>>>> *Stack total noise*
>>>>
>>>> *Exposure Count*
>>>>
>>>> *Stack Total Time*
>>>>
>>>> *Stack total noise*
>>>>
>>>> No Filter
>>>>
>>>> 10
>>>>
>>>> 3491.44
>>>>
>>>> 48.37
>>>>
>>>> 21
>>>>
>>>> 7332.03
>>>>
>>>> 70.09
>>>>
>>>> 31
>>>>
>>>> 10823.47
>>>>
>>>> 85.16
>>>>
>>>> 41
>>>>
>>>> 14314.92
>>>>
>>>> 97.93
>>>>
>>>> 52
>>>>
>>>> 18155.51
>>>>
>>>> 110.29
>>>>
>>>> Optolong l-Pro
>>>>
>>>> 6
>>>>
>>>> 3808.85
>>>>
>>>> 50.14
>>>>
>>>> 11
>>>>
>>>> 6982.89
>>>>
>>>> 67.89
>>>>
>>>> 17
>>>>
>>>> 10791.73
>>>>
>>>> 84.4
>>>>
>>>> 23
>>>>
>>>> 14600.58
>>>>
>>>> 98.17
>>>>
>>>> 28
>>>>
>>>> 17774.62
>>>>
>>>> 108.31
>>>>
>>>> Optolong l-Enhance
>>>>
>>>> 1
>>>>
>>>> 3174.04
>>>>
>>>> 45.43
>>>>
>>>> 2
>>>>
>>>> 6348.08
>>>>
>>>> 64.25
>>>>
>>>> 3
>>>>
>>>> 9522.12
>>>>
>>>> 78.69
>>>>
>>>> 5
>>>>
>>>> 15870.2
>>>>
>>>> 101.59
>>>>
>>>> 6
>>>>
>>>> 19044.24
>>>>
>>>> 111.29
>>>>
>>>>
>>>>
>>>>
>
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