Picking the correct exposure for Deep Sky

[admin]

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

[sikd]

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

[admin]

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

[sikd]

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

[admin]

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