First Light ZWO1600GT - Lum only

[TrevorW]

ZWO camera 1600 GT, scope EON110ED, Lum filter only run 85 x 2 min subs - Gain 139 offset 50 - where am I going wrong, no DBF- captured. Using NINA the HFR was around 3 and HFR SD .43 average. Guiding with PHD2 was average RMS error tot diff of around 0.24PIX or less- This has been processed in SIRIL and PS with noise reduction in Topaz AI ???

[AlexN]

Not 100% sure, because everyones rigs will produce slightly different HFR's because of arcsec/pixel ratios and also local seeing conditions - but for me, HFR of 3 would be considered grossly out of focus.

Your image does not look out of focus, but it does look like almost all the stars are saturated entirely, and while the black point does not seem clipped, there does appear to be sharp drop offs from a certain signal level.

Have you confirmed your offset value to be correct? I had similar (not as dramatic) cutoff when my offset was too low, as the dimmer areas of a target got heavily lost in the read noise. After I bumped up my offset considerably, I very rarely get the issues anymore unless I'm imaging something VERY dim, at which point I just need more data.

Do you have the ability to put the stacked/unprocessed files into google drive or onedrive or something so I (or someone better than me hopefully) could take a look at the data. It would be possible then to determine if the data is at fault, or processing.

If its data - then I'd look at the offset value as the first reason... a too high or too low offset can cause all types of issues with data

[TrevorW]

Thanks Alex, I have yet calculated offsets using the NINA plug-in - I have just used the AF function returning HFR values around 2.4 for LUM - hopefully my next data set will be more in tune, like they say "watch this space" - there is definitely a steep leaning curve moving from OSC to Mono and at this stage I will be concentrating on LRGB Ha until I become proficient
:)