Crayford focusser problem??

[Thales]

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

[Moonshane]

https://www.google.co.uk/url?q=http://www.teleskop-austria.at/information/pdf/SWN1507eq3_Skywatcher_Crayfor-Auszug_justieren.pdf&sa=U&ved=0ahUKEwjKx6fix-vOAhUMChoKHeXkDlIQFggOMAE&usg=AFQjCNHWoznOHO3769TL8G7i8B49FKp2dg

[SkyBound]

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.

[Thales]

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!

[Dave In Vermont]

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

[Moonshane]

Normal adjustment is fine I should think. The key is do tiny adjustments to the tension grub  (I mean like 1/30th of a turn (maybe 1mm of end movement on the Allen key) until you get just enough tension.

[Thales]

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

 

[Moonshane]

The one that needs a tiny tweak is the bigger central one above the silver locking thumbscrew.

 

[Moonshane]

Ps usually this adjustment is all it takes.

[Thales]

Welll knock me down with a feather!  Yes it seems to have worked!! YEEEESSS!! Cooooolll! Yes it's the middle one and a couple of nudges seem to do it.

THANKS A LOT!!

Happy nights!

Jeff

[Thales]

I should also add that you SGL people are pretty awesome!

[Dave In Vermont]

I just checked my 10:1 Crayford on my ST80. It's the one made for ST80's and other small refractors. It does does have the one bolt. The others on my Cassegrains have two-bolts.

I'll leave a photo,

Dave

 

 

[Moonshane]

This Is the monorail type focuser and they are slightly different I agree.