The second imaging run for the Iris Nebula – NGC 7023.
Things went a little better. I realized that i had forgotten the field flattener on the AT106 for the first imaging run on Sept 5th. So i added that to the image train and made moderate effort to align the camera to the same orientation. The field flattener is not a reducer, so i was counting on being able to combine the subs from both sessions. The corners would be a bit soft but better than without.
The imaging run went ok with a little more time than expected to centre to object in the FoV. The scope does not point well to the north. Perhaps a better PA would help that.
I started the imaging run at about 11pm EDT and setup the imaging run for 6hrs which would take me to astronomical twilight. At 5am i went out to shut things down and found that after 130min (13subs) i lost guiding. Perhaps it clouded over, but i am suspicious that the previous run also had the same error at 130min. That being that FlexRx reported two large a flex rate.
So again i got 2hrs of data when i was expecting 5-6hrs.
I did a quick stack and processing and found that there was a large dust blob that the flats could not remove. Probably on the field flattener. Mental note – check and clean the optics and sensor before an imaging run.
I combined the two image runs together and then repaired the “hole” caused by the dust blob by copying that piece from just the run 1 data. It was a bit tedious to create a mask and blend the offending area so that it was not too noticeable.
The image after calibrating and stacking with the custom tools and processing more carefully is here: