Sunday night turned out to be successful night using the flats and darks. I ran some experiments to confirm what breaks things and what doesn't. I think I have figured out all the ways I can screw up and how to avoid them.
Here is my workflow as I have documented for myself. The values you see in parentheses are values specific to me and will probably be different for you. I am using ZWO 294MC uncooled camera and SharpCap. You will see some all caps, that is me a reminder to me to pay attention to this step.
Set image train as plan to image
Make sure all spacers and camera are tight
If using filter, place it in
DO NOT CHANGE IMAGE TRAIN. If do so, will need to redo flats
Determine the image sizes that want to use
(4144x2822, 2816x2822, 1920x1080)
For imaging, determine values that will be using for
○ Exposure (6s, 12s, 24s)
○ Gain (300, 400, 450)
○ Brightness set to (10)
○ White Balance Red set to (50)
○ White Balance Blue set to (50)
○ Filter (No, Yes)
Using white t-shirt method during the day. Make sure no direct sunlight is hitting the front of t-shirt. Or can use dew shield.
For each combination of image size and filter of Light values need to capture a Flat.
In my case I have 3 sizes times 2 filter which gives me 6 flats.
Make sure there is nothing in the Dark Subtraction "Preprocessing" area
Set Gain to between 200-300
Adjust exposure such that the white channel around 50%. The highest color no higher than 90%
BRIGHTNESS SET TO ZERO. Does not matter what doing for lights
White Balance Red set to value using for lights
White Balance Blue set to value using for lights
No Bias selected
Rename file with size and if using filter. Example with filter 'F4144.png'. With no filter '4144.png'
Capture after sunset so temperature is within 5-10C of imaging temperature. Camera temperature is shown in SharpCap. (Want to test to see if doing this at room temperature causes issues)
For each combination of size, exposure and gain, need to capture dark
In my case, I have 3 sizes times 3 exposures times 3 gains for 27 total flats
Set exposure, gain, brightness, White Bal ® and White Bal (B) the same as you will use for capturing light frames
All The Things I Have Done Wrong
Here is a list of all the things I have done wrong while capturing flats and darks or when using them.
• When capturing flat, allowing direct sunlight on the t-shirt
• After capturing flat, forgetting to set brightness back to 10 when capturing dark
• After playing with SharpCap Brain tool, forgetting that it changes brightness and not setting it back to 10. Exposure and gain change but I remember to change those back.
• Not having my image train tight, so it loosens during the night
• After a failed plate solve, changing exposure or gain to plate solve. Then forgetting to change back
• While imaging, changing the exposure or gain for the new DSO and forgetting to change the dark and flat to match
I hope this makes sense and helps.