Hi Alex,
what binning configuration did you have set up? If you had 'averaging' binning, which is default, your e/ADU for the 2x binning will be 4 times larger than the raw value of 0.25, which I think would account for the difference. Testing unbinned would help remove any confusion regarding how the binning works.
cheers,
Robin
Picking the correct exposure for Deep Sky
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Re: Picking the correct exposure for Deep Sky
Hi, Robin
I overlooked the binning. Thank you.
By the way, how do other basic sensor parameters change when binning is changed?
I think Full Well does not change,
Dark current increases proportionally to the square of binning,
Read Noise increases proportionally to the square root of the number of binned pixels.
Does SharpCap calculate all these parameters for different binning when analyzing the camera sensor?
Alex
I overlooked the binning. Thank you.
By the way, how do other basic sensor parameters change when binning is changed?
I think Full Well does not change,
Dark current increases proportionally to the square of binning,
Read Noise increases proportionally to the square root of the number of binned pixels.
Does SharpCap calculate all these parameters for different binning when analyzing the camera sensor?
Alex
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Re: Picking the correct exposure for Deep Sky
Hi Alex,
in terms of the suggested exposure times, because CMOS cameras only ever do binning *after* analog-to-digital conversion, the choice of binning has no effect on the suggestions or the correct exposure/gain settings. This is different for CCD cameras where the binning happens by adding the charge from the binned pixels before ADC conversion.
Going back to the results after binning for CMOS cameras, the end result is the signal to noise ratio will improve by the square root of the number of pixels being binned - whether the noise is reduced or the signal is increased to achieve this depends on whether you use averaging or additive binning.
cheers,
Robin
in terms of the suggested exposure times, because CMOS cameras only ever do binning *after* analog-to-digital conversion, the choice of binning has no effect on the suggestions or the correct exposure/gain settings. This is different for CCD cameras where the binning happens by adding the charge from the binned pixels before ADC conversion.
Going back to the results after binning for CMOS cameras, the end result is the signal to noise ratio will improve by the square root of the number of pixels being binned - whether the noise is reduced or the signal is increased to achieve this depends on whether you use averaging or additive binning.
cheers,
Robin
Re: Picking the correct exposure for Deep Sky
Hi, Robin
Thanks again for the explanation.
Which pixel size for CMOS and CCD should be entered in SharpCap online calculator in case of binning - physical or binned ?
Alex
Thanks again for the explanation.
Which pixel size for CMOS and CCD should be entered in SharpCap online calculator in case of binning - physical or binned ?
Alex
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Re: Picking the correct exposure for Deep Sky
For CMOS you should use the unbinned pixel size. For CCD you could either use the unbinned size then multiply up the rate by the binning factor, or use the binned size - either would give the same result in the end.
cheers,
Robin
cheers,
Robin
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Re: Picking the correct exposure for Deep Sky
Hi Robin,
Very quick question. Managed to get first light on the my new camera and immediately ran the smart histogram to get some sub exposure times. I had done the calculation manually based on C*(r^2/P) and then multiplied the result by 3 for a OSC camera. But I get a different number than the Smart Histogram return. My calculation gives a result of 28.32 but in SH the result was nearer 19s. it looks closer to result from the formula * 2 rather than * 3.
Have I missed a step anywhere?
Many Thanks
Anthony
Very quick question. Managed to get first light on the my new camera and immediately ran the smart histogram to get some sub exposure times. I had done the calculation manually based on C*(r^2/P) and then multiplied the result by 3 for a OSC camera. But I get a different number than the Smart Histogram return. My calculation gives a result of 28.32 but in SH the result was nearer 19s. it looks closer to result from the formula * 2 rather than * 3.
Have I missed a step anywhere?
Many Thanks
Anthony
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Re: Picking the correct exposure for Deep Sky
Hi Anthony,
no, that sounds fairly good agreement, it's probably a bit lower that the rough calculation because the green channel gets measured by default and that is usually most sensitive and has a lot of the sky brightness in it these days. The rought calculation misses out all of that sort of detail about different channel sensitivities or colours of the light pollution.
cheers,
Robin
no, that sounds fairly good agreement, it's probably a bit lower that the rough calculation because the green channel gets measured by default and that is usually most sensitive and has a lot of the sky brightness in it these days. The rought calculation misses out all of that sort of detail about different channel sensitivities or colours of the light pollution.
cheers,
Robin