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Strange autoguiding


Gtech
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Set up last night and merrily started imaging. After about two hours I started to get almost repeatable DEC drift (12-15arcsec) every 40 secs whilst PHD was OAG.

I switched to guiding with AstroArt and the same thing happened. Each time I reselected the drifted star in AstroArt, the DEC drift would be almost identical (amount, time and duration) but in the opposite direction.

I decided to shutdown the whole rig and stat again. I then spent 3 hours trying to resolve and gave up at 2:00am as my subs had eggy stars.

This is the first session where I've seen such a repeatable drift. Nothing has changed parameter-wise and I've manged 6 hour session without issue 

Polar alignment was good, scope balance was good.

Looking at the logs in both PHD and AstroArt, the 40 sec interval drift doesnt correspond with any drive component.

I also checked battery voltage and there was no issue.

Weird this one...

Your thoughts appreciated before a pull the mount apart again!

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I would say that one of your Dec guide connections is not working. I see a Lodestar in your sig, which is exactly what I was expecting to find!

The tiny, flimsy cables are abominable on this otherwise excellent camera and I suspect that one of them has died. Often a wiggle on the cables is all you need. I get this quite often since I'm running two Lodestars here. You can bind the cables together, tape them in loop back onto the camera body, attach them to an extension to support them... I've done all of these things and when I get the bad connection problem I just change the cable route, probably back to how it was before I cured it the previous time.  :BangHead:   There is no rhyme or reason here, the cables are just too flimsy.

Olly

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I don't use the ST-4 cable with my Lodestar - just the USB looped back and fastened to the body with a velcro strap.  Since I did that I have had no problems with it.  Guiding uses EQMOD/ASCOM with PHD.  I have had problems at times when changing scopes but this has been due to ASCOM settings.  DEC wandering off constantly one way or the other.

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Strange, I loop back the USB cable and attach with a velcro wrap to the Lodestar body.

Up to now most of my subs have been north side of the Meridian, last night, when it happened, I was working on M33 and the scope was South side....I marginally change the RA balance to compensate but kept the DEC as-is (slightly camera heavy).

I also noticed that it was down to -1c, lowest temp I've worked to date.....coincidence?

Whilst posting this Fedex delivered the ADM saddle so I may pull the DEC axis apart later today before fitting. 

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4 hours of subs tonight and not a hiccup, its lookimg like it might have been the USB lead afterall. I made sure it was lashed down with a velcro strap and and a rubber band.

The new saddle is sweet!

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