Focus move request fails to converge

FocusCube v1 & v2, Zero, Motor Focus Kit (Universal or Zero)
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Joined: Fri Aug 26, 2022 6:08 pm

Focus move request fails to converge

Post by shadow »

My focus cube v2 been acting up the last two nights out. It runs normally when controlled either from the Unity platform or when given explicit move commands within NINA, but fails when I'm running a sequence and change the filter. (I have a monochrome setup with a ZWO EFW.) I'm using filter offsets in the NINI autofocus setup and therefore the focuser is asked to move each time the filter changes.

It fails this move request. It seeks back and forth around the requested position and never settles. If I wasn't watching, it would continue this all night!

This doesn't always occur. Occasionally it does the move quickly and Nina starts recording the next image, which is the expected behavior.

In my autofocus settings I have been using a step size of 200, overshoot backlash, 100 steps, OUT (0 IN). This used to work fine. As a matter of fact, the autofocus routine works fine. Very clean hyperbolic convergence with no backlash visible in the wing of the hyperbola.

I've used this setup many nights in the past with no problems. But not now.

A bit of testing this morning shows that by increasing the backlash setting from 200 to 500 fixes the problem. I may try this tonight, but I'm worried this behavior may be a symptom of a deeper problem.

Or, are non-convergent focuser moves expected when the backlash setting is too low?

Other background info: telescope is WO GT71. I'm running NINA Version 2.0 HF1 RC004.

I checked the grub screws on the focus cube shaft and they're tight.
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