strange periodic spikes in DEC guiding

[Ofer Goldberg]

My mount is the iOptron CEM70 with RA encoder.

Lately, I experience strange periodic spikes in the DEC guiding.

The spike happen in both directions and are resolved after 10-15 seconds (picture from phd2 is attached).

the system is well balanced and polar aligned.

Does anyone have a clue on what is happening here?

Thanks

Ofer

[Bruce Waddington]

Hi Ofer.  This is a hard one to figure out, I think you'll need to some incremental testing.  There have been numerous reports on other forums of iOptron mounts with absolute encoders not behaving well with guiding.   In your case, I think the first thing to do is disable the PHD2 Dec backlash compensation and see what happens.  It would also be a good idea to run a much longer session with the Guiding Assistant so we can see how the mount behaves on its own for an entire worm period.  If we can get a look at the results after doing these things, we can probably help you figure out how to get better results.  We do have some new features in PHD2 for use with encoder-equipped mounts so those might be useful once we have a better understanding of what's going on.

Regards,

Bruce

[Ofer Goldberg]

Thanks Bruce,

I actually disabled the backlash compensation and saw similar behavior.

I will make much longer guiding assistant session and report.

Two things I didn't mention earlier:

- It seems that the spike were somewhat smaller in size and duration after I made encoder calibration.

- The effect was much more significant after the meridian flip (this is the graph attached. guiding was OK before MF).

Regards

Ofer