Crayford Vernier Adjustment

[pjphilli (Peter)]

Hi
I have a Ritchey Chretien 200mm f8 GSO scope fitted with GSO Crayford
focuser. This has a 10:1 vernier knob. I am using a Canon 400D camera which is fairly heavy so when the scope is in the near vertical position
the Crayford focus adjustment has to be able to move the camera "up hill". Hence, the firmness that the adjustment shaft needs to be increased by the adjustment screw so that the camera does not cause the focus to slide back and that firm upward and downward adjustment may be maintained using the main knobs. However, I notice that the 10:1 vernier adjustment seems to have only a weak affect on the focusing movement, ie in the above circumstance the vernier will move the camera down but there is not enough torque to move the camera up.
Is there any way that I can improve the torque applied to the movement shaft by the vernier knob? I hope this all makes sense!
Cheers Peter

[gmbfilter (Geoff)]

You need correct tension adjustment
See this http://www.backyardvoyager.com/gsofocuser.html
This will stop the draw-tube and the 10:1 nob slipping
You wont need the complete service but the article helped me get my head around focuses

[gmbfilter (Geoff)]

Originally Posted by kinetic

Great link Geoff...wow if I had known that link existed I wouldn't have made my own pull to bits thread.

Peter, one thing to add to Geoff's link is that it is important the
ball bearings seat into a tiny dent in the small shaft.
If they don't do this the shaft can slip out sideways.
See here:
http://www.iceinspace.com.au/forum/s...ad.php?t=76809

I agree that a little grease and a tweak of the tension on this
'vernier' setup worked wonders. It lifts my DSLR and
camera/filterwheel much better after doing as Geoff's link
details.

Steve

Wow great stuff cant believe I missed it
Sorry about hijacking your thread Peter

[pjphilli (Peter)]

Thanks Geoff and Steve for the very useful guides that will allow me to tackle the vernier with confidence. Cheers Peter

[pjphilli (Peter)]

Just a follow up for those who may be following this thread. The solution to my slipping vernier adjustment was cured by tightening the nut on the
focuser shaft behind the main/vernier knobs. The tighter the nut the more positive action of the vernier but there is a trade off in increased general
stiffness in focuser movement by the main knob. You don't get something
for nothing!
Cheers Peter