How To Determine The Optimal Subexposure Level For Astrophotography

Many beginning astrophotographers are confused about how long each of their subexposures should be. I know that was true for me!

There is a lot of good information on the net but I wasn’t aware of anything that covered the process from beginning to end so this video does just that.

This is what it covers:

  • 1. The formula for optimal exposure level
  • 2. The range from minimally acceptable to optimally good exposure levels
  • 3. How to measure the parameters of your camera
  • 4. How to estimate when you can’t perform the measurements (perhaps you are considering buying a camera and want to see how it would compare to your current camera).
  • 5. How to evaluate your individual subs for exposure and clipping in PixInsight
  • 6. How to evaluate your subs in Sequence Generator Pro

Here is the link to Jon Rista’s post on Cloudy Nights: https://www.cloudynights.com/topic/597682-i-need-a-primer-on-read-noise-calc-asi1600/#entry8200280

Here is the link to the page where you can find the 2DPlot script as well as many other useful PixInsight scripts: http://www.skypixels.at/pixinsight_scripts.html.

This video doesn’t get into theory but concentrates on practice. I hope this is helpful. If there is anything that isn’t clear or you find a mistake, please let me know.

ERRATA: When I discuss the scaling from the camera bit depth to 16 bits, I erroneously said the scaling was 8 for the ASI294 when it is actually 4. Proof something three times and I still don’t catch an error until it is out the door…

Below is an excel spreadsheet that implements the formula as described in Jon’s post as well as in the video:

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