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Cumbria Jon

Skywatcher - have I damaged the drive mechanism?

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I am wondering if I have knackered the drive mechanism on my Sky-Watcher Skyliner 400p Flextube Synscan Go-To Dobsonian ?

WHAT I DID: I did a quick collimation in daylight, and needing to swing the tube from vertical to horizontal I stupidly slackened the fixing hand nut on the wrong side, NOT slackening the drive release wheel on the correct side.  Then I forcibly swung the scope from vertical to horizontal with the drive mechanism still engaged.

WHAT HAPPENS NOW:  The scope is fine optically of course, and both drive mechanisms (the 'compass' movement, and the vertical) appear to work fine, they sound normal and the scope moves at the normal speeds as far as I can tell. BUT, I cannot get it to align, for the GOTO system.   When I do a two star alignment – I line up the first star, no problem.  When the scope moves to suggested second star, it gets very close on the horizontal, but not close on the vertical  – the axis which I forced the mechanism on.  Previously, once aligned on the first star, the scope would move automatically to within a degree or so of the second, and only need minor readjustment.  Of course I can move to align with the second star using the drives, but nevertheless, the alignment remains way off, 10 – 20 degrees off, which big errors particularly in the vertical axis, when I move to any other objects.

I suspect I have damaged the drive / encoders.  Does anyone know if a moderately practical amateur can repair these – or indeed replace them?

Meantime I am learning how to find objects without the Go-To, which I find difficult – but rewarding.  Thanks in anticipation for any advice.

Jon

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Presumably the encoders are calibrated to recognize a certain home position or 'zero' position, a position from which they start their count. The manufacturer requires you to level the base so I guess this is ultimately where the home position gets its information.  I'd guess that you have accidentally shifted either the moving or fixed part of the altitude encoder so that the zero position is now incorrect. By looking at the mechanism physically it might be possible to see what has moved. It might be externally visible or might not. Getting a look at a normal example might give you a clue. There might be a drawing which would do instead. I doubt that you've broken anything since it works mechanically but you are likely to have displaced it.

Olly

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Thanks Olly,  I'm steeling myself to take it apart cautiously, when the weather abates (it's in an observatory in a dark field - not easy to get it indoors).  I'll look for anything that gives a clue about the zero - or vertical or horizontal fix for the altitude encoder.

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