Adding motor to focuser

[symbiosis]

Hi all

Decided to start on a little project and make my focuser motorised. Firstly, my scope has a fairly cheap rough n ready rack and pinion focuser and I cant afford to upgrade so I'm going to have to adapt this. I've seen several projects that involve step motors (relatively expensive) or servo motors (a lot cheaper) - so I'm going with a servo for now.

I've also seen a lot of designs and most seem to involve some kind of either pully system to turn the focuser wheel or adding a cog to the pinion arm and turning that. Just wondered though, why cant I just remove one of the focuser wheels and directly attach the pinion to my motor? Is it to do with gearing and the amount of energy required to move the focuser? Has anyone done what I'm proposing successfully?

My other question, does anyone know how to remove a pinion wheel, I've examined mine and cant see how it's attached to the metal rod

Any help/advise much appreciated

[JAS]

The Skywatcher auto focuser fits as you have described,

On mine there was a screw in the middle of the knob! You just remove it, and bolt on the motor. There is a flexible joiner between the two.

Jason

[nigelg]

Have a look at the SharpSky focuser @ http://www.dt-space.co.uk/SharpSky_Kit/.

Nigel

[JamesF]

My Mak motorised focuser uses a drive belt and gears down by 5:1 AFAIR. It's quite nice to be able to tweak the focuser by the tiniest amount whilst imaging. For visual it may not actually matter so much.

James

[JAS]

You could also look at the SGL observatory automation group here: http://tech.groups.yahoo.com/group/sgl_observatory_automation/

They have an arduino based focuser project.

Jason.

[Bizibilder]

I use a belt drive onto the existing focusser wheel, which works very well. One major advantage of this method is that I can slip the belt off easily and operate the focusser in the normal way - this is often necessary for rough focussing, the electric focusser, mine is a servo unit, is only used for fine focussing. Overall it works very well indeed. Have a look here: http://stargazerslounge.com/topic/91973-fiddling-with-an-autofocusser/page__hl__%20focusser%20%20bizibilder

[symbiosis]

Thanks for the replies all, having a rather more pressing issue to deal with right now as I'm being flooded :-( will take a look at the suggestions when it finally stops raining!

[Gina]

The Skywatcher unit is a DC motor with gearbox.

I use a much cheaper motor with plastic gearbox but use belt drive from that to the focus knob. I got mine from Maplin but other suppliers sell them. The orange plastic gears are a tight fit on the shafts with the green ones freely turning. By pulling the orange gears or the plastic collars off you can change the gear ratio. Each gear pair gives a 4:1 reduction.

Here is where I'm using these motor/gearboxes to focus camera lenses for my wide-field narrow band rig. These lenses need a tiny amount of movement to focus.

Finally, this thread http://stargazerslou...focussing-unit/ shows how I used one of these motor/gearboxes to control a dual-speed Crayford focuser using belt drive. Full details of the construction and control circuit are given.

Your application falls between the two extremes above and I should think somewhere between the 2 and the 4 gear pairs should work.

Hope that helps

[Gina]

Thanks for the replies all, having a rather more pressing issue to deal with right now as I'm being flooded :-( will take a look at the suggestions when it finally stops raining!

Oh dear - hope it isn't too bad. It's dreadful weather we're having We're on the side of a hill and rarely get bad flooding. The worst was when a culvert got blocked above us and we had a stream through our sheds. It didn't quite come into the house.

[BuzzBomb]

My Mak motorised focuser uses a drive belt and gears down by 5:1 AFAIR. It's quite nice to be able to tweak the focuser by the tiniest amount whilst imaging. For visual it may not actually matter so much.

James

How have you attached this to your Mak James? Any photos at all please?

Sent from my GT-I9001 using Tapatalk 2

[JamesF]

How have you attached this to your Mak James? Any photos at all please?

I wrote it up here:

http://stargazerslounge.com/topic/135260-127-mak-motor-drive-focuser/

James

[symbiosis]

Fortunately (for me) the flooding stopped 3 doors down - wasn't good for my poor neighbors however. I'm hoping tonight will be a little less exciting.

Some great (and very ingenious) suggestions here shame I cant really afford an off the shelf option so its going to have to be DIY all the way. I think I'm going to start simply and I'm considering the linked two servo motor idea at present - are there any major downsides to this solution that I should consider?

[andrea1984]

Hi all

Decided to start on a little project and make my focuser motorised. Firstly, my scope has a fairly cheap rough n ready rack and pinion focuser and I cant afford to upgrade so I'm going to have to adapt this. I've seen several projects that involve step motors (relatively expensive) or servo motors (a lot cheaper) - so I'm going with a servo for now.

I've also seen a lot of designs and most seem to involve some kind of either pully system to turn the focuser wheel or adding a cog to the pinion arm and turning that. Just wondered though, why cant I just remove one of the focuser wheels and directly attach the pinion to my motor? Is it to do with gearing and the amount of energy required to move the focuser? Has anyone done what I'm proposing successfully?

My other question, does anyone know how to remove a pinion wheel, I've examined mine and cant see how it's attached to the metal rod

Any help/advise much appreciated

I'm not even able to remove the wheel from the rod, even after removing the screw.

Attaching the photo.

Thanks