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Help, please - something is wrong with my integration 🙁
Apologies for the late reply...
Thanks Wouter. No the camera is a fairly new 5D mk iv and I use it for my landscape and wildlife photography so not going to modify it.
Please see my reply to Vincent above for some other information.
I have tried integrating with 4 different sets of flats and the result is always the same. If I get similar results with the 400mm I will know it's me and not the hardware at fault. I will do as you suggest and cover the viewfinder. I may do covered and uncovered to see if there is any difference 🙂
FWIW I have a Hotech SCA flattener as well and I have never seen rings and rainbows like you do. I am pretty sure that the flattener is really, really good.
Well to add another voice, as I said earlier, I had (have) a bad vignetting problem, and it IS due to my field flattener! However, my image train is very different from Stephen's: Nexstar 8 (2032mm FL), Astromedia f/6.3 Focal Reducer/Field Flattener, Canon T7 connected through a 1.25" T-ring & adapter.
This is about 60 minutes worth of 60 second subs, calibrated with darks, flats, and bias, some stretch but no other processing. Clearly a huge amount of vignetting.
I removed the flattener, and this is the result:
This is about 75 minutes worth of 60" subs, calibrated with darks, flats, and bias, more processing than the first picture, but also, no trace of vignetting! Clearly the FR/FF is introducing the vignetting. What I don't understand is why the flats didn't eliminate it.
Also, the terrible vertical artifact below the nucleus in the second picture is, I think, a hair inside my camera. It does show up on the flats, but the flats, again, don't eliminate it from the final image. Has anybody seen anything like this, and any tips on how to get rid of it?
Interesting, thank you. When I have time this weekend I will remove the flattener and create a masterflat without it. Will post back here when done.
It has to be something in the setup at least, it's an optical effect and can be caused by these optical attachments in combination with something else like the light source. This is also why it's difficult to solve from our side as it's very specific to your setup. But you'd indeed have to take this step by step and try to find what influences this. Good luck!
Hi guys, below is a new master flat taken without the Hotech SCA field flattener on my SW ED80. If it is not my imagination there is still a slight hard ring on this flat
A reminder of the flat with the flattener:-
I suspect the issue is therefore with the ED80 and made worse with the addition of the flattener.
Going to use the Canon100-400m II for a while now instead, 70 minutes on M33 yielded this which isn't too bad.
Not sure where all the red comes from in this though!
'...Canon T7 connected through a 1.25" T-ring & adapter. '
Do you really mean a 1.25" T-ring (31.75mm)? I don't know this reducer but 1.25" seems a considerable restriction. Are you able to test with a T2 (42mm) or M48 (48mm) connector to see if this resolves the issue?
Mike, we may be talking past each other. This is my setup:
A standard Canon T-ring with a 1.25" eyepiece adapter. Are you saying that something like this:
would be better for reducing vignetting with my f/6.3 focal reducer? Thanks.
I think it very likely that the 1.25" eyepiece adaper is causing vignetting in your set-up.
I imagine that the light cone from your scope plus reducer is diverging too fast to pass unobstructed through the 1.25" diameter restriction.
I wouldn't want you to spend money solely on my suggestion so hopefully Vincent might also comment.
Yes, 1.25" will cause more vignetting if your sensor is covering that light path (you notice these even more with a fullframe camera). Been a while since I had my setup so I have to dig a bit from memory, but I believe I attached a Coma corrector directly to the Canon, which I think was a 2" opening. Still had some vignetting, but that was to be expected for a fullframe camera I used.
Ordered. It's not that much money and I can send it back but suspect it will help in any case.
Now, any speculation on why my flats do not eliminate this vignetting -- or, for that matter, the big defect that is on my non-focal-reducer image of Andromeda above?
At the moment not really sure no, these are very difficult to pinpoint as it's hardware specific, I can only suggest some things that might help but I would also advice to check with someone local to you (like a observatory) to go over the setup maybe.
Well, I received my 2" adapter, and I'm sorry to say it did not help with vignetting on Andromeda. Perhaps slightly, I could dig up the image. However, the 2" adapter is a superior setup for regular use and I will be using it in the future.
I suspect that my issue is that I got the cheapest available field flattener/focal remover. I should have spent the extra money for the Celestron one designed for my sct. Lesson learned.
PS - in general, I would say that Andromeda is not a good target for my setup with it's long focal length. It is so huge with nebulosity everywhere that it highlights vignetting and makes background subtraction very difficult.
Oh that's a pitty, good it does help in the setup though! Keep us posted if you get to a better result, would be good to know.