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Crayford focusser problem??


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Hello telescope sages!

I was out with my SW Equinox80 last night, which I bought mainly for looking at star fields and such like, and I noticed that having focussed on some stars overhead the drawtube would slip further out (even with the focussing knob locking cap in place).  Certainly with the scope at 90* the focusser will let the drawtube out but it slips at certain points and then doesn't draw it back in.  It is fine whiile horizontal (!!) or maybe up to about 45* tilt and works as nature intended.

I have only attached a diagonal and an eyepiece (I've never attached anything more than EP, diagonal and barlow at any one time).  The focusser certainly wouldn't work I'm sure with something like camera attached.

Am I doing something wrong? Or am I overlooking something? The drawtube stabilises and stays rigid when the locking screw beneath the focusser is tightened but then you have to loosen the screw when changing EPs to refocus and the drawtube then slips.  I've had the scope about 10 months and can't recall it behaving like this before.

 

Any words of wisdom most welcome!

Thanks

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Hi,

Is there not a tension screw as well as the locking screw, sometimes you need a small Allen key to alter it....most Crayfords have a tension screw of some sort......seperate to the locking screw which is normally a thumb screw.

:)

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HI Moonshane, thanks a lot for that.  It certainly looks like it has the exact bearing on the problem!  At first sight it looks a bit A level as opposed gcse where I'm at, I wonder if I attempted this I'd break a guarantee, as I've had the scope less than a year??? eek! I will give this some thought!

Thanks for posting the article - I will go over it carefully!

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All of my Crayford 10:1 (I have 3) dual-focusers have 2 thumbscrews on the underside. The 1st. one (closest to the OTA) is kept totally loose. The 2nd. one I adjust - tighter for heavy loads, looser for smaller ones. Pointing at the zenith and trying to rack it back in is how I determine how tight it needs to be.

Great focusers!

Dave

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Many thanks everyone for the discussion.  I attach a picture of mine - it doesn't quite look like the one in the pdf from Austria, and certainly needs allen keys of some kind I would think,  The locking screw, there is only one, so hmmm not sure which is the tension screw and which the 'parallelizing screws'.... eeek

 

crayford.jpg

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