Optimal Exposure and Noise Calculator

[joseph.mcgee at sbcglobal.net]

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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