Cone Error? Or something else? - Forums

Topic starter

2 hours ago

Hi all,

I was imaging the other night right next to Polaris (Declination 88 degrees).

I discovered after the Meridian flip that the image was no longer centred at all or even in the field of view.

Cone Error is the culprit I assume.
I have noticed slight frame rotation after meridian flips before, but in this case, once I got the target manually centred after the flip, the degree of rotation was extreme.

So much so that I had to crop an insane amount out of the stacked image.

I’ve attached a screenshot of the final stacked image so you can see how much rotation was involved.

The only thing is, I would have thought that the diffraction spikes would be misaligned with cone error and they are not.
I hope the axes on the mount are not the issue but I don’t know how to go about checking definively in any event.

Would appreciate any input on this as I’m sure there are many more experienced than me that might have encountered something similar.

Gear in question:

2600MC Pro

150PDS Newt

EQ6R-Pro

ASIAIR

📷 Screenshot 2026-04-15 at 14.47.06.jpg

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Tony Gondola

Frequent contributor

Exemplary contributor

1 hour ago

I doubt that the mount could be off that much. When I have seen this it’s usually do to something in the imaging train getting loose and rotating.

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Lynn K

32 minutes ago

When you say “Cone Error", I am assuming you mean cone error in the mount's orthogonality. Un-orthogonality in a mount will cause bad star alignment when the mount is flipped. You can test this by simply looking through an eyepiece visually after the mount is flipped. Plate Solving usually solves this problem and re-adjust the star alignment.

Mount Un-orthogonality should not cause rotation. For that to happen there needs to be rotation in the optical axis. More likely, something is loose in the optical train and the weight distribution caused by a meridian flip is causing the camera or something in the optical axis to rotate.

Lynn K.

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