QSI660 flats with NINA flats wizard

[Geordie mc]

I’m having issues getting good flats from the NINA flats wizard with my QSI660. I’ve set adu as 25000 with 10% tolerance. I’ve tried sky flats and flat panel. They just don’t look right and with narrowband the exposures are very long. I see no vignette game, indeed I seem to have a slightly brighter edge round the image and a few strange dark bands that don’t change with t-shirt, paper etc diffusing the light. I can see a couple of clear dust motes but I think there should be more. If anyone is using the QSI660 and could help I’d be very grateful.

[teoria_del_big_bang]

Can you upload a flat so we can see.

I have a pretty bright flats panel that I have to use a filter for to dim it on Lum flats, and exposure time is still less than 1 second, but with my Ultra NB filters exposure time for flats can be 60 seconds or more, without the filter, so for NB it is not ideal but also not unusual.

Steve

Edited March 15, 2021 by teoria_del_big_bang

[Geordie mc]

Thanks Steve. Sounds like I’ll have to use 2 runs of the NINA flats wizard with a much brighter light source for  NB. I’ll try them again and see if they make any difference. As I don’t really see any vignetting with this scope/ccd combination I might just try to keep the optics as dust free as possible and skip flats altogether. Even those taken with lum filter and short exposures just look odd. No clear nights for a bit so time for some experimenting I think. 

[david_taurus83]

How do they calibrate your lights? Have you tried?

[Geordie mc]

I haven’t tried them. They looked so wrong I thought I’d done something wrong so I deleted them thinking I’d retake as sky flats and all would be good. As soon as I started retaking they looked the same. They have a lighter border all round the edges. There’s a couple of dust motes and some odd dark patches running at an angle in the lower left. No dark corners. They look really grainy when stretched too. I think I’ll try with much lower adu target level. I can’t have exposure times for narrowband running beyond 60 seconds with a bright light panel. It would take me several hours to shoot the flats each time. I’ve heard the QSI660 has a full well capacity around 12000 in high gain mode which is the mode recommended for 1x1 binning. Maybe. Should be aiming for half. Of this and not Alf of 65000? I’ll try again today and use whatever I get to calibrate and see what happens. I’ll report back.

[Geordie mc]

Update. Hope this may be useful to others. I have now discovered that the ascom driver for the QSI660, which you must access before you connect the camera in NINA, defaults to low gain but also will default to high speed download rather than high quality, if you took and saved any snapshot images at the end of you last session. These factors probably are the cause of the long exposure times and grainy results I got. However, after rerunning the flats wizard today the flats still seem odd. Some filters show a brighter border round the image edge. Others seem to have a more expected vignette to them, while the red filter has a clear  gradient - bring much darker on the left side and extending halfway across the image. I’ll try calibrating my lights with them tomorrow and see what happens.