background gradient

[prabhakar]

Hi,
I'm working on processing "witch head nebula" using startools, and for some reason i see white gradient on the background.
Could this be due to wrong flats or something i'm doing wrong with processing?
Here's my processed version http://www.astrobin.com/154277/

I've added fits here.
https://www.dropbox.com/s/3y4uho1zn4nrs ... 5.fit?dl=0
Regards,
Prabhakar

[admin]

Hi,

Did you apply flats? The image seems to suffer from vignetting. With an image-filling nebula like this, it's hard to distinguish between real nebulosity and gradient for Wipe...

[prabhakar]

Hi Ivo,
Yes this version is calibrated with flats, i will try with my old sets.
Thanks
Prabhakar