APT Flats Aid Tool with ZWO 294MC Pro

[Deeko]

Hello,

I am confused with the CCD Flats Aid histogram in APT and what it is supposed to look like when taking flats for my OSC ZWO 294MC Pro. I have read around for advice for flats exposure length for the 294MC and it seems you really want to be >3 seconds to avoid noise to create proper flats. I can achieve this no problem by using several layers of t-shirt with an adjustable LED panel. I take the flats with the IDAS D2 light pollution filter which is designed for LED street lights, so now I wonder if using an LED panel + D2 filter is actually  messing with the histogram? Attached is the histogram - could someone please give me some advice on what the histogram should look like roughly for my setup (294MC + IDAS D2). In the attached screenshot I have used the APT flats aid tool to arrive at a 4 second exposure for  25000 ADU.

D.

[DougM43]

Not sure if it’s any help but when I take flats in apt with my OSC camera my histogram shows three separate peaks,

I assume it’s a separate peak for red, green and  blue so perhaps your filter is having an effect on the histogram. How much or if it matters though I don’t know.

Doug

[Deeko]

I can get three separate peaks if I substantially lower the exposure time, but with the 294 the informed consensus seems to be that flats of 3 seconds or longer are necessary, accompanied by an equal exposure length for dark flats (forget bias with the 294).

[ippiu]

i always take flats of 0,5 sec or 1 sec at gain 150 -200.  Peak Histogram at 45-50%: single rgb peaks range from 20% through 80%. They are perfect. (read the sharpcap manual)

I also did some tests of differente exposures ranging from 0,1 to 4 seconds: i didn't see any substantial differences...

[Deeko]

9 minutes ago, ippiu said:

i always take flats of 0,5 sec or 1 sec at gain 150 -200.  Peak Histogram at 45-50%: single rgb peaks range from 20% through 80%. They are perfect. (read the sharpcap manual)

I also did some tests of differente exposures ranging from 0,1 to 4 seconds: i didn't see any substantial differences...

As soon as I get a clear night I am going to do some testing  with 3-4 second flats with the same exposure time for dark flats, no bias images. I am not unhappy with the images I can collect and process but feel I could do the calibration better to result in cleaner images. This is all the more so after reading around more on taking good flats with the 294.