Duplicate star images with autoguiding - Help please.

[Hawklord]

Two nights ago I tried to image the Horsehead (tricky little blighter isn't it?). I had to ditch about a third of my subframes because the final images showed 2 star images instead of 1. I'm using PHD on a GPDX with starbook-s. The PHD settings are all at default. Guide camera is the 16ic on a WO 66. I have noticed that when PHD is callibrating, the number of steps was about 30-40 for N&S (and took much longer to move) whereas it was <10 for W and E (and was quick). Is this relevant? The guidespeed on the starbook is set at 1x. Do I need to change the settings on PHD or does it have anything to do with the short FL of the guidescope (386mm)?

Any suggestions as to where to try next? I might just revert to using the skysensor 2000 if it relates to the starbook.

Example 3 min subframe crop enclosed.

[steppenwolf]

This effect can be caused by a slipping clutch or a snagging cable. With regard to PHD, if the calibration is satisfactory, the calibration steps do not really matter. I would say this is a 'mechanical' issue of some kind, could even be a loose focus tube?

[Starflyer]

What does the PHD graph look like, can you see large jumps? Is the setup well balanced?

[Hawklord]

Doh! Hadn't thought about the graph. I'll tighten up all the nuts and bolts etc and enable the graph next time I try it out. Cheers.

[roundycat]

were you by any chance guiding on what could be regarded as a double star?

Dennis

[narrowbandpaul]

you could have balanced the mount too well!

this causes the teeth to oscillate, put the RA balance slightly out, so that the scope wants to move in the direction of the motion of stars...(i think this is east side)