Replacement focuser?

[osbourne one-nil]

My Vixen NA140SS has a 2" rack and pinion focuser with a planetary reducer. It's very very rough though. The best way I can describe it is when you turn it, it's like driving over rumble strips and if you happen to find focus on the top bit of the rumble strip, it wants to rock backwards or forwards to a low bit....if that makes sense? 

I've taken the mechanism off and the roughness (or clickiness) seems to come from the bearings in the reducer. Obviously I'll get back to the dealer who I'm sure will sort it but what if I wanted to change the focuser...would that even be possible? I can't imagine there's anything made to fit one of these scopes with 140mm tube threaded on the end?! Or is it possible to buy just a replacement mechanism and keep the draw tube?

Does any of this make sense?!

 

 

 

[Stu]

I'm fairly sure Moonlite would have something which would fit. You obviously need to ensure it works with the Petzval elements correctly but I would contact them and see if they have an adaptor available

[osbourne one-nil]

That's a thought - the Petzval looks like it might be part of the focus draw tube according the the Vixen diagram I've seen so that could be awkward. Hadn't thought of that. 

I'll drop them a line anyway but I think the one I have will need replacing anyway. 

[Stu]

Useful thread here. Looks like it should be possible

http://www.cloudynights.com/topic/410513-vixen-na140-ssf-focuser-attachment/

[osbourne one-nil]

Cheers Stu - you're better with Google than me! So it looks like the big flanged part holds the corrector lenses and there's an additional inserted bit which is the focuser. That sounds doable and also sounds like Moonlight should know all about this. 

Brilliant!

[Tinker1947]

Maybe try a E-Mail to FLO they stock a few types...

http://www.firstlightoptics.com/moonlite-focusers/moonlite-cf-crayford-focuser-for-refractors.html

http://www.firstlightoptics.com/starlight-instruments-feather-touch-2inch-crayford-focusers.html

[ollypenrice]

It may just be that the pinion is meshing too tightly against the rack and needs to be brought further away. This is likely to be adjustable. It would strike me as a shame to move from a rack and pinion to a Crayford. Vixen mechanical engineering is usually simple, practical and honest.

Olly

[osbourne one-nil]

No, I've tried that and it's all ok. The "roughness" appears to be coming from the planetary reduction housing (which might be something I've just invented) - the ball bearings behind the focus knobs because I've removed the actual focus mechanism from the draw tube and the roughness is still there when you turn the knobs. 

[Knighty2112]

Have you made sure that the grease on all the moving parts is OK and not contaminated with anything? Might be worth cleaning all the grease out and putting some fresh grease in to all the gears/bearings.

[osbourne one-nil]

Just to update on this - in case anyone else is ever affected...they just replaced the focuser and the new one is perfect. Green Witch were very helpful and it was easily sorted. 

[Dave In Vermont]

I was just reading this thread for the first time! That's a happy ending - great to hear!

Dave