argh - lightbridge focus prob

[sejanus (Gavin)]

So I go to give my 16" first light as it's clear - but the focusser is not working.

When you turn the focus wheels, the main barrel does not move up or down

dummy question - are focussers serviceable by idiots i.e. me?

I am wondering if I should disassemble the thing to find the problem, or just take it into bintel

any ideas anyone?

thanks heaps

Gav

[Tannehill]

what kind of focuser (style type?) came with it?

Does it have two knurled knobs on the barrel? If so, try loosening one or the other, then both, then tightening each in sequence, and see if your focuser moves. If you have a Crayford style focuser, that may be the reason. Mind you, if you have one very loose, the draw tube might be too loose and not move with the focuser travel, and too tight ditto, but dabble with that and see what you get.

st

[sejanus (Gavin)]

it's a 2" crayford - I'll go play, thanks

[Tannehill]

on a crayford, one is a locking screw (to prevent motion during photography, for exampe) and the other is a tension adjustment.

if you don't have a crayford, then that isn't your problem, obviously....but I'm no focuser expert so someone else could weigh in....


s

[GrahamL]

Try .. loosen the bottom (focuser lock )and adjust the tension with the top .

[sejanus (Gavin)]

thanks guys

by making the 2 screws (very) loose it now focuses, albeit a bit sloppily

I'll play with the 2 independently and try and find a good mix

[StarLane]

Forget about the focus lock screw for the moment, just concentrate on getting the tension right on the thumb screw closest to you.
I had the same drama when I got my first Crayford. The focuser draw tube doesn't move till the tension screw is adjusted a little. It shouldn't be sloppy but just enough tension to move the draw tube in and out with the weight of an eyepiece.