Flat too strong? (pixinsight)

[NickK]

On the left is the original image. In the middle is the master flat and on the right is the calibrated image after image calibration has been applied.

any thoughts on this?

[Tim]

It does seem to have overcompensated doesn't it?

Maybe trial and error with pixelmath to subtract the flat at various percentages would help in this instance?

When you took the flats, how was the ADU count individually? I've always had best results with peak ADU around 22-23K with a 16 bit camera.

Must admit, I dont use PI for stacking or calibration Much prefer the simplicity of DSS.

[ollypenrice]

I can't cope with PI stacking either and use AstroArt 5. As Tim says, it must surely have over-compensated somehow. You need Harry!

Olly

[harry page]

Hi

As olly well knows I use AA5 for image calibration , easier than PI I am afraid However

Over correction normally occurs when

1) Flat is not correct i.e over exsposed

2) Bias / dark frames not applied to lights and flats correctley or not at all

Have you tried this flat in another app ?

Harry

[FrankieValley]

My thoughts are that possibly the surface you are illuminating for your flats is not evenly illuminated or that the light is not being evenly diffused into your setup. It also looks like the flat is too bright. These are details of my equipment for making flats http://stargazerslounge.com/diy-astronomer/172367-embroidery-hoop-flats-screen.html#post2120105

I've attached a histogram for my flats, which look grey rather than white, as yours does.

[NickK]

It's a EL panel with a t-shirt infront. Usually I use 3 second exp and do 75% well capacity but this has managed to get closer to 90% with a 4 sec (no saturation).

It was, however, the first time I've used the EL panel with my A80mf piggybacked. The Vixen doesn't stop the panel being placed flat but does mean it's a little offset from what I have done before however it seems to match the pattern geometry correctly but I think it's the brightness that's the problem.

[Tim]

I think that's too bright Nick, try going to 35 - 45%