Is there a simple process to solve this?

[assouptro]

Hi Starpeople! 

I have been taking advantage of the last spell of clear nights here in north west Lancashire imaging NGC 4565 

I’m using a 12”Meade sct balance on my azeq6 with an Atik 460 binned 2x2 filter wheel, astrodon filters and Celestron oag 

I have an unusual configuration using an Alan Gee flattener/reducer and it has given me a focal length of around 1750 (can’t remember exactly, I’ll have to work it out again if you want the exact fl) 

I am imaging at 1.06 arc seconds per pixel 

anyway, the Alan Gee device is designed to go directly into the baffle but I have it reconfigured after the oag, in fact it protrudes into the oag otherwise the prism casts a shadow on the camera chip due to the smaller diameter of the Alan Gee unit

I have tried this configuration before and although I get a severe vignette I can normally control it with flats.

I have ended up with an annoying circle effect that I cannot remove in App or  with DBE in Pixinsight (although I have to admit I’m not very confident with Pixinsight 

This is with light pollution removal in APP

Stacked image 

before LP removal tool

after 

 

Pixinsight 

before dbe 

after dbe

It’s a tricky one 

should I redo my flats, increasing the integration time? 
I currently use a flat panel with a dimmer and stick to 1s at about 26000, I read that increasing the length of the flats can help?

I also tried using DBE in “axial” mode followed a tutorial by Adam block on YouTube  which is a great watch even if it doesn’t work for my image 

Sorry for the long winded description 

I am trying to avoid having to use something like clone stamp tool in ps 

Thanks in advance for any help 

Cheers 

Bryan 

[michael8554]

Hi Bryan

Seems to be all about the Flats, so can you post one ?

Could be reflections.

If the FR is first you get a wider choice of guide stars, can't you raise the prism to stop it shadowing the imaging camera ?

(If the OAG is before the FR, do you have the full FL in the guide prog, just checking ?)

Michael

[assouptro]

Hi Michael 

Thanks for getting back to me 

Here is a single blue 1s flat

blue_003.fit

With regards the oag prism 

the prism is as low as I can without clipping the chip and I have experimented with this Alan Gee telecompressor  in all different positions too 

I really struggle to get guide stars when the prism is behind the telecompresor as it clips the prism, any lower and it clips the chip! 
And yes, I am guiding at full focal length and PhD knows it. 
 

I ended up going back to an old configuration last night using a Celestron 6.3fr/ff (still behind the oag) and the images I got so far seem to be nice and flat and fairly even, I’ve still got to process anything but the guiding was exceptional for this mount, the weight of my equipment and the focal length I was at!

3 min blue sub

the guiding graph

This of course now prevents me taking new flats so I will have to find another way to solve this issue 🙄

Cheers 

Bryan