Star distortion

[Lee_P]

Apologies if this has been covered before -- I'm sure it must have been but I couldn't find the info so thought it best to ask. Since using a Sky-Watcher Light Pollution filter on my ED80 with Field Flattener, my astrophoto results are improved but the stars in the outer parts of the frame have become lines pointing away from the centre. I think this is field curvature..? Any suggestions on how to improve it? Is there an easy way in Photoshop, for example?

[Leveye]

Post an example if you could.

[RikM]

I am not sure but having the filter in-line might mess with spacing required for the flatner.

[Lee_P]

Ah yes, sorry, I should have attached an example in the first place.

[Alien 13]

The effect shown in your image usually means that the FF to sensor distance is too close and needs adjusting with spacers.

Alan

[blinky]

I think it needs to be 55 mm from the sensor although this sometimes needs a small tweak of say 1-3 mm either direction to get things perfect!