Hello,
My Oiii data has always shown radial gradients, which don't appear in any other filter. To minimize it, I need to apply several steps of gradient removal (DBE) and after the first pass, I tipically get the following:
(note: all photos shown here represent two hours of integration and were shot with no Moon. Slightly cropped, one DBE pass applied, noise reduction applied and STF stretched)
panel flats
The corners still have a strong glow and right next, a dark ring shows up. I have been living with it but recently decided to tackle it and upon a conversation with a friend, it was suggested that I might have internal reflections. Upon checking, I confirmed that indeed such reflections existed, mostly coming from focuser tube. Hence, I flocked the focuser drawtube and all the optical path until the camera (focuser + reducer + extentions + filter wheel). The improvement was significant, at least when looking with the flat panel in front.
This week I managed some hours of clear sky and shot the same target to see if I had any improvement. The result below, after first pass of DBE:
(note: the vertical streaks are caused by a plane passing on its approach to the airport)
panel flats
sky flats
In regards to the brightning in the corners, I definitely see an improvement for sure. However, the dark rings keep appearing.
Does anybody have an hint on what might be causing them?
Telescope: TS Optics Triplet APO 115/800
Reducer: TS Optics 0.79x
Filter wheel: QHY CF3, 7 positions, 36 mm
Camera: QHY 268M
Thank you in advance.
My Oiii data has always shown radial gradients, which don't appear in any other filter. To minimize it, I need to apply several steps of gradient removal (DBE) and after the first pass, I tipically get the following:
(note: all photos shown here represent two hours of integration and were shot with no Moon. Slightly cropped, one DBE pass applied, noise reduction applied and STF stretched)
panel flats
The corners still have a strong glow and right next, a dark ring shows up. I have been living with it but recently decided to tackle it and upon a conversation with a friend, it was suggested that I might have internal reflections. Upon checking, I confirmed that indeed such reflections existed, mostly coming from focuser tube. Hence, I flocked the focuser drawtube and all the optical path until the camera (focuser + reducer + extentions + filter wheel). The improvement was significant, at least when looking with the flat panel in front.
This week I managed some hours of clear sky and shot the same target to see if I had any improvement. The result below, after first pass of DBE:
(note: the vertical streaks are caused by a plane passing on its approach to the airport)
panel flats
sky flats
In regards to the brightning in the corners, I definitely see an improvement for sure. However, the dark rings keep appearing.
Does anybody have an hint on what might be causing them?
Telescope: TS Optics Triplet APO 115/800
Reducer: TS Optics 0.79x
Filter wheel: QHY CF3, 7 positions, 36 mm
Camera: QHY 268M
Thank you in advance.
