Flats issue driving me mad !!!

[Skipper Billy]

OK - so the camera and filter wheel are off the scope and I took flats with the filter wheel facing straight down onto the flat panel - exactly the same result - dark at the top and light at the bottom.

So I took the filter wheel off - camera straight onto the flat panel - same result.

I am clean out of ideas now.

This image is from the camera straight onto the flat panel - I tried it rotating the camera 90º - same result. This is stretched and converted to JPEG for ease of viewing.

 

[david_taurus83]

The corners are black! Surely an email to Atik?

[Skipper Billy]

1 hour ago, david_taurus83 said:

The corners are black! Surely an email to Atik?

Its brand new from FLO so I am dealing with them.

FLO have always been excellent at sorting problems so I must give them fair opportunity to resolve the issue without me going over their heads.

I guess FLO will be in contact with Atik as this is the second camera - the first was exactly the same and was requested to be sent back and exchanged for this one. The chances of two cameras with exactly the same issue must be incredibly small !!

I keep hoping its me doing something stupid but I am fast running out of ideas.

 

 

[vlaiv]

Well I did flat / flat calibration and results are not what I would call a success:

However, I would not immediately jump to conclusion that above did not work because of camera - it had a reason not to work (at least I think so) - Upon inspecting flat names, I noticed that ~5s one was luminance filter, and ~22s one was red filter?

I'm not sure if this should work for two different filters, and I strongly suspect that it should not completely - as dust at least will be in different places. There is also fact that camera sensitivity varies with wavelength and two different filters will have different relative sensitivity of pixels.

Anyway, what ever the reason - above flat/flat calibration is a fail - it does not represent uniform noise distribution - "gray field".

[Davey-T]

2 hours ago, david_taurus83 said:

The corners are black! Surely an email to Atik?

Indeed, according to Maxim some pixels are at zero in your JPEG. 

Dave

[Skipper Billy]

OK - I have reduced the brightness of the flat panel with more ND film to get longer exposures.

This is the result - untouched - straight from the camera resting on the flat panel ie no optical train. No stretching and way long enough to avoid shutter shadow. (15 seconds +)

What do you think - be honest!

 

 

Target 1_15.03sec_1x1_OIII flat_frame1.fit

[Skipper Billy]

and here's a Lum

 

Target 1_8.89sec_1x1_Lum flat_frame1.fit

[Davey-T]

Looks OK as far as pixel values go, all in the 20000 to 30000 range, looks strange but maybe they will work.

Dave

[Laurin Dave]

Hi David

There are Flat Field images in the Atik 16200 manual that don't look too dissimilar to yours (or mine)..   ie darker at the top than the bottom (because of stretching and clipping)  I'd speak to them if you haven't already, maybe its a  characteristic of the chip.

Dave

[Big Jim Slade]

I'd post one of mine but it won't be much help as I have everything connected with M48 adapters so I have a fair bit vignetting.

You're showing a 2.2% difference between top and bottom in that image, so the stretch is making it look far worse than it is.

 

EDIT: Just compared one of yours to one of mine, and while they are visually pretty different, the MAD values are with 4 (yes four) of each other.

[Skipper Billy]

Thanks folks - I guess I will just have to wait for a clear night and get some lights taken then see what happens.

Thank you for all your input.

David (aka Skipper Billy)

[Skipper Billy]

Quick update - FLO are in discussions with Atik to see whats going on here. Will post the outcome when its concluded just in case anyone else has the same issues and finds this thread.

A BIG thank you to everyone who has helped along the way.

[Adam J]

On 19/03/2019 at 18:26, Skipper Billy said:

With my last setup - Tak 106, EFW3, Atik 460EX I used a flat panel and got a nice steady set of flats every time.

The only thing that has changed is the camera - I bought an Atik 16200 and the top of the frame was much darker than the bottom.

I tried a different light source, rotated the light source - both of them and rotated the camera in 90º increments - nothing made any difference.

I discussed the matter with FLO and a sticky shutter was thought to be the issue.

The camera was exchanged for a new one.

Just tried it - guess what - exactly the same issue.

See attached - just stretched and converted to Jpeg. this is a 5 second 1x1 exposure so it shouldn't be shutter shadow.

This has got me beaten into submission.

Anyone have any ideas what to try next ???

 

What exactly are you using as a flat panel? Try changing the rotation of the flat panel and see if the gradient rotates. 

Edit: I now see you tried that.