New to ASTAP, help needed

[Stewart]

hello all,
i have been testing my new scopw with ASTAP to check for tilt and curvature, and i attach one of the results, so it looks like tilt is not too bad at all, but i see the square is showing a bit of curvature which i think could be better, but can someone please tell me by the shape of the lines whether the flattener needs to be moved away or closer to the sensor, my guess would be away, but am not sure, as ATM i have it bang on the recomended 55mm, (or 63 with the included 8mm adapter), this is on an Esprit 100 with dedicated flattener.
thanks
Stewart

[Stewart]

nobody can help with this....

[han.k]

Stewert, your image looks good to me. I don't thing you will get much better. You can try but I can not advice which direction would help if any. I would just leave it.
Han

[Stewart]

hmm, so why are the sides of the square not straight lines, i though they should be for the minimum amount of curvature, i would assume that when the lines go inwards , as in my image, this means that the spacing needs to be increased on the flattener...correct...??

[Darren L Hill]

Hi Stewart;
I've never had a flattener or flattener-reducer yet that could perfectly correct a mass produced scope 100%. 90-95% of the image being flat seems to be the best of these. What do the stars look like in the image at the edges, and what would be your estimate of flat?

[Stewart]

thanks for the reply
the stars are not great in the farmost corners, and with CCD inspector i get this which shows 18% curvature
and the actual image, with no calibration frames, just a light stretch..oh, and also not cropped at all, taken with my Esprit 100 with QHY268m and a Optolong L-pro filter..1 hors of 3 min subs...

[han.k]

The measurement is sensitive. Optics are never perfect. It only indicates a small curvature. partly maybe mixed with some tilt and optic imperfections. Maybe you can get it a little better but likely when the telecope is in an other position or at an other temperature it can come back.