Question Large declination backlash reported by PHD2 guiding assistant

I have just bought a used M-Uno and am puzzled by the following quote from you tech support "what the PHD2 software calibration notice as a "backlash" it is the belts elasticity behaviour, that comes with the Belt Drive System"

This mount is advertised as FAST REVERSE and ZERO BACKLASH. I think the PHD2 test just ramps the DEC in one direction and then reverses back to where it started. It would appear that upon direction reversal there is a large amount of backlash the the test shown. It doesn't matter whether the delay is from gear slop or belts stretching in the end it's a delay at the scope to the requested movement.

Can you please show another type of test result to backup the claim of FAST REVERSE and ZERO BACKLASH.

Rick

Hi Stefano,

meanwhile I tweaked my settings a bit. I went back from ZFilter to Lowpass2 and especially increased the guiding speed in Dec to 0.95 (I was not able to enter 1.0, is there any reason for this?) My RA guiding speed is set to 0.8. But you can derive those settings from my PHD logfiles I guess.
As you can see the average was at 0.88" after nearly 4hrs - much better than the 1.x" I normally achieved. However, I hope you can detect some room for improvement in my settings as during the next night the results were not as good anymore which also might have to do with the seeing conditions. I also played with the Auto Adjust feature but couldn't detect any immediate improvement.

Attached you can find two guiding logs. After changing the settings I did not run the Guiding Assistant again in order to check if those strange declination backlash results I reported initially would have been improved. I'll try that next time.

Regards,
Stephan

PS: Unfortunately the forum settings are much too restrictive to upload meaningful data, like a zipped PHD logfile of more than 100kb, please reconsider those settings. Instead I upload two screenshots now where you can see at least my settings and the resulting RMS error. I zoomed into the dither regions where you can see that Dec typically needs much more pulses to get back on track than RA. What is the reason for this behaviour?

Sorry for the small images. I attached full size screen shots, is there any way to avoid downscaling of images to such an unreadable size?

I managed to insert pictures here in a more useful size... I think my settings and the graph should now be better readable.

Total RMS of 0.88"


Total RMS of 1.07"

I can't read the screenshots. You should be able to attach a zipped PHD2 GUIDE log which is not very large. The DEBUG log is the big one.