Another flat problem

[roundycat]

Hi all,

I took a set of flats the other night using my LX200, TV reducer and ST10. Without exception the RGB and Ha flats all work well. The luminance flat is a bit odd. See attached. Can anyone suggest what might be the problem. The polo mint impression shows even at max value stretch and over corrects the lights to a damaging extent.

I use a white board lit by doubly diffuse light and it works for my other scopes. I wonder if it is something to do with the TV reducer which is being used with a focal length over twice what is recommended. Absolutely nothing changed between the two except for the filter wheel. Either way, why does this problem only affect the L flat and all the others are perfect????????????????

The first correct answer will receive my everlasting gratitude, for what that's worth!

Dennis

[centroid]

Hmm!, the 'polo mint' looks like star test on a well collimated SCT

Certainly an odd result Dennis, and even more odd that its only on the luminance .

Can't speak for the TV reducer, as I use a Celestron 6.6 FR on my LX.

I use more or less exactly the same setup as you, that is a white board, illuminated with a difuse white light.

After my recent post, re problems with the 'flats' upsetting the colour, I've now resolved that one and my recently 'posted' M65 image had a 'flat field' applied to it, without any problems.

So, in your case, I would guess that there's something funny happening with the TV reducer, and that there's now't wrong with anything else.

Dave