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You want to set your exposure according to the read noise on your camera. Aim for an exposure where the histogram peak corresponds to between 5x and 10x the read-noise squared.
You can look up the read noise on the ZWO website - it varies with gain.
You have to convert the read noise to the numbers you see on the histogram using the gain in e-/ADU, offset and number of bits in the camera.
For example: for the ASI071 at unity gain (94) the read noise is 2.6e-
So 10 x RN^2 = 68
Offset is either 20 or 65 (depending which driver) - lets say its 65
And it is a 14 bit camera
So you first convert the 68 to ADU by dividing by the gain in e-/ADU which at unity is 1.0
So you have 68 ADU
Now add offset of 65 which gives 133
And multiply by 4 to convert to 16 bit equivalent which gives 530
So expose till your histogram peak is around 530. Its not highly prescriptive. But longer exposures offer little extra benefit over more subs.
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