Optimal Exposure and Noise Calculator

Sat Mar 4 19:19:43 GMT 2023

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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