Smudges, Flats, filters, what's happened here?! Atik 460EX mono

[Fordos Moon]

Hi all,

I have added this extremely roughly prepared image to try and demonstrate my concerns.

It is a mere 5x300 secs RGB image using the ATik 460EX and baader RGB filters (EFW2) and not even aligned in this version but that is not the issue. 

There are 2 smudgy areas centre left and right and I am trying to fathom them out, also a large colour gradient in bottom left and top right corners. Oh and the satellite trail in the blue channel which I could lose with more subs and kappa sigma stacking.

I have recently imaged with very pleasing results, but this one worries me.

Is is possible my flats could no longer be working? They worked fine with earlier images but are they the cause of the blurs now?

And how come the gradient I have not had that before?

My plan is to remove all and clean my filters, polar align again and retake flats. Also I note my Atik vents are pointing upwards - could dust/anything have got in there and should I turn the camera so the vents point downwards?

My set up:

Earlier images with same set up, and same flats:

[frugal]

Don't you need to take fresh flats every session in order to account for dust bunnies and dirt? From the sounds of your post you are reusing the same flats from session to session.

[swag72]

I was going to mention taking flats after each session as well, but as you gave a picture of your setup and I now know it's in an obs, from my experience I'd say that its not an issue to use the same flats......... assuming that you don't change the camera orientation at all. I've been using flats that are about 5 months old.

I would do a couple of things - Firstly look and stretch each channel on it's own and see if you can identify if there is a channel where the gradient seems to be creeping in. It could be that your flats are giving you issues just in one channel and then when you merge them you are ending up with this problem.

You've not changed anything with your integration process have you? Perhaps moved to a different programme for example. So that something has changed about the way you calibrate?

Just a couple of thoughts and where I'd start looking anyway.

[Oddsocks]

It is rather difficult to assess from the posted jpeg due to the compression artefacts but looking at the individual colour channels in PS the brighter stars in the affected areas have fuzzy halos which are not present in your earlier pictures, makes me think there may be a thin condensation layer on the cover glass of the camera, or on one of the surfaces of the corrector.

I sometimes experience this problem in spring and autumn in my observatory mounted OO ODK 10 and QSI camera as there is no air circulation between the camera and the telescope's built in corrector element and I need to remove the camera from the image chain and let the air circulate behind the corrector to dry out that part of the image chain.

I know quite a few astronomers run a dehumidifier full time in their observatories to minimise the problem but the cost of running one 24/7 is a bit beyond my means these days!

You would need to look at a stack of your lights only, without calibration, and stretch to see if the artefacts are visible, if so condensation is the most likely culprit.

[ollypenrice]

How good was the sky? Thin passing haze could do all that damage quite easily. Yes, as Oddsocks says, it could be mist on the chip window or filters but the sky would be the first suspect to me.

I don't reshoot flats until they stop working, which might be a year. I recently had a new bunny (from the chip window) and redid them - but then the new bunny disappeared and I just went back to the previous ones! Bone idle...    I've also discovered that I can rotate the cameras without issue since all the bunnies come from things fixed to the cameras and the focusers, of good quality, remain concentric.

The unusual gradient also has a strong whiff of sky quality to my mind.

Olly

[Fordos Moon]

Thanks all I think sky quality and haze may well be the issue but I will explore all the options you mention! I really appreciate the advice thank you

[Fordos Moon]

Just to confirm the smudges are happening tonight on all filters - time to remove and reattach the camera?!

[BVietje]

Fordos,

Sara hinted at this, but didn't ask explicitly:  did you rotate the camera to change the way the target is framed?  That could cause your flats to be out of register and give you weird artifacts.  You obviously know lots about processing and imaging from the images you posted, just wanted to be sure you considered rotation.

[Fordos Moon]

Fordos,

Sara hinted at this, but didn't ask explicitly:  did you rotate the camera to change the way the target is framed?  That could cause your flats to be out of register and give you weird artifacts.  You obviously know lots about processing and imaging from the images you posted, just wanted to be sure you considered rotation.

Hi Brad, good thought but this time I hadn't rotated anything. Last night however I took all the bits apart and gave them a good clean and I hope that will sort it. Although now i have the task of rotating the frames i took last night to try and combine them with the ones i took before, a process im not quite sure how i am going to approach!