Motor focuser belt advice needed

[Jessun]

Hello,

I have a Rigel n-focus stepper motor, and I have a Moonlite focuser that I would like to connect somehow. I could splash out on a Moonlite flange and focuser kit, but it seems a bit of a waste since I have a unit that worked with the original Orion (GSO type) focuser.

I'm thinking about using some sort of tiny belt to drive the focus wheel and I ask fellow DIY fans for advice on where to find something suitable.

Appreciate any help!

/Jesper

[JamesF]

If you want to drive the focuser knob directly I think it's common just to use an O-ring with a V pulley on the end of the motor drive shaft. On my Mak I took the knob off entirely and fitted a gear wheel instead. That is driven by a toothed timing belt.

James

[Jessun]

Cheers James,

I have searched around and found this:

http://www.motionco.co.uk/timing-belts-timing-belts-c-25_45_27.html

I wonder if that can do the trick along with some pulleys....

/Jesper

[Bizibilder]

Jesper - those are the belts I use on my electric focusser. If you put the belt onto the focusser knob directly there will be sufficient grip/friction for a positive drive - even with low belt tension.

[JamesF]

I used them too:

http://www.tanstaafl.co.uk/2012/02/skywatcher-127-mak-focuser-motor-drive-conversion/

James

[opticalpath]

Hi Jesper.

Several members have used successfully the MXL belts and aluminium pulleys from Motionco that you mentioned. I have fitted stepper motors to two scopes using them, including one with a Moonlite focuser. They work very well.

http://universalcons...user_pentax.jpg

and

http://universalconstant.com/focuser_MN190.jpg

Adrian

[JamesF]

Hi Jesper.

Several members have used successfully the MXL belts and aluminium pulleys from Motionco that you mentioned. I have fitted stepper motors to two scopes using them, including one with a Moonlite focuser. They work very well.

http://universalcons...user_pentax.jpg

http://universalcons...cuser_MN190.jpg

Somehow your MN190 link takes me to the Pentax image as well. This looks right:

http://universalconstant.com/focuser_MN190.jpg

James

[Bizibilder]

Found a pic for you:

[opticalpath]

Sorry ..... I've corrected the link.

Adrian

[Jessun]

Great, guys! Some very neat mods you have put together there. The problem with the Moonlite is that it is seems tricky to bolt anything onto. It's like fitting a motor focuser to the monolith from 'A Space Oddysey'.... I like the long belt version as shown, but how well does it do a v-curve?

/Jesper

[opticalpath]

............ The problem with the Moonlite is that it is seems tricky to bolt anything onto. It's like fitting a motor focuser to the monolith from 'A Space Oddysey'

/Jesper

You're right. I ended up attaching a plate to the spacer block under the focuser base plate. But that only works with the square focuser base for reflectors - don't know what I'd do with the Moonlite on a refractor. Maybe some kind of in-line co-axial connection directly from motor spindle to the focuser spindle would be possible. Then you would just need something to prevent the motor body from rotating ...... which might be easier to arrange.

Adrian