Today I did a bit of Google searching and found some very useful information from Jon Rista who I've always found to be a reliable source. The thread is at the link below and Jon's post is the second post in the thread.
https://www.cloudynights.com/topic/5700 ... 00mm-cool/
The fifth post in the thread shows Jon's discussion in equation form. I put the equation into Mathcad and produced the following graph:
ASI1600MM Target Average by STEPHEN KING, on Flickr
The Horizontal axis is the ASI1600MM Gain setting.
The vertical axis is the Target Average Counts (16 bit) you want to achieve with your exposure. There is a curve for ASI1600MM Offsets of 10, 20 and 50. I measure Target Average Counts using the Pixel Aid tool in
EXAMPLE: For a Gain of 139, and an Offset of 50 you should aim for a Target Average Counts of about 1300. Adjust the Exposure length to achieve the desired counts. The desired counts will ensure that you have a long enough exposure to achieve optimum Signal-to-Noise while still maximizing your Dynamic Range.
I haven't had a chance to try this out yet, and, am looking forward to giving this a try tonight if the fog will stay away long enough. The exposures I've used so far have been much longer than this analysis suggests, and, many of the stars have been saturated. Hopefully this will improve the quality of the data I collect. Clouds come in tomorrow, so, tonight will be the only chance to try for a while.
Hope you find this useful.
Cheers,
Steve