Cone error

[Anthonyexmouth]

I never see anyone discussing cone error, I remember when I first started watching an astronomyshed video about it but never seen it really mentioned again. How does it manifest in images if it's an issue? 

[ONIKKINEN]

Go-to inaccuracy and difference in image orientation pre and post meridian flip come to mind as potential issues.

The first is of no concern to any imager who uses plateolving, the initial go-to will be inaccurate anyway so nothing lost here (except maybe the 10 seconds spent on the first slew).

The second, change in image orientation, increases in effect the higher you point in declination and could well be an issue if you are shooting a mosaic with tight tolerances or a target that generally just barely fits the FOV at some specific camera angle. I have had fairly significant cone error (and still have) and have seen up to 3 degrees of difference after a meridian flip when shooting M81. Not an issue for my FOV but could be for some kit. For targets at lower declinations its of no concern at all.

[GalaxyGael]

And for those using OTA that cause diffraction spikes, cone error is similar to OTA rotation within the rings, changing the position of the secondary spider with respect to the sky and cause pre- and post-meridian flips to stack so that diffraction spikes don't align.

[wimvb]

Cone error causes field rotation, noticeable after a flip. Cone error should be corrected by an X/Y-movement after an ideal flip. Instead, you move the mount in RA and DEC to recentre the target. It's a nuisance when imaging near the celestial pole, but the further away from it you get, the smaller the problem is.