help with Bracket on BT-200 Newtonian, for focuser

[Astroman (Andrew Wall)]

Hi all,

Anyone here know how to attach a bracket on a Bintel 8" f/4 Newtonian focuser, so a stepper motor could be added for automated focusing?

I have a set of gears to go from a stepper motor to the knob on the focuser, which will give me a 2:1 ratio. I tried to do this on the 10:1 knob but there was too much play and was giving irregular focusing, I had a bracket I made up but it was very rough, and had to hold it on with another set of rings, I don't really want to do this on the other side as there is not enough room. I had hoped that the existing screws on the focuser could be used, or can they?

Anyone with a Bintel 8" f/4 scope been able to motorise the existing focuser?

EDIT: Or should I do away with the belt drive and attach the stepper motor directly to the shaft? would the stepper have enough torque to move it?


Appreciate all the input.

[Shiraz (Ray)]

It's a problem Andrew. I ended up making up a bracket out of fairly heavy Al and attached it directly to the OTA with strong double sided tape. Tried 10:1 and direct shaft attachment, but found that 10:1 was best for my low torque stepper, provided the side load on the shaft was adjusted so that it was just enough to stop the drawtube from slipping. Regards ray

[astro_nutt]

Hi Andrew.
Would you consider using a belt made from tie-down webbing or similar to secure the bracket to the optical tube. Just a thought.
Cheers!

[Astroman (Andrew Wall)]

Originally Posted by astro_nutt

Hi Andrew.
Would you consider using a belt made from tie-down webbing or similar to secure the bracket to the optical tube. Just a thought.
Cheers!

Hey that's not a bad idea, might use that in conjunction with Ray's idea of using double sided tape. I know it's not going to last 10yrs but it sounds like a good idea. I thought of using the Double sided tape but thought it would create a little bit of flexure. May even bite the bullet and drill the OTA. Now I got my stars round again I think it's a keeper.

thanks guys...

[tlgerdes (Trevor)]

We made a bracket out of Al to mount the skywatcher motofocuser to the focuser. We just replace the screws with something a little longer. The bracket was drilled and cut to attach to 3 of the screws of the focuser.

Took about 2hrs to make.

[astroboof (Steve McN)]

Hi Andrew
, funny I should find this as I have a spare eq5 Dec motor handy and have recently been contemplating the same move. Reckon i would go down the alloy bracket path but no design yet.

If possible, I' like to see any pics guys, to help the motivation, especially while the weather is el stinko.

Cheers and cs
Steve Mac

[astroboof (Steve McN)]

Oh my guess is the motor should have plenty of torque for the focuser providing all is set well. They seem to cope with plenty of resistance moving a 10 or more kilo scope rig about even when we forget to adjust counterweights and tube rings for motion or slewing.