102 Mak focuser

[heliumstar]

Hope someone can chime in with experience and/or ideas.

So the focuser on my Mak is kind of stiff and sometimes hard to focus due to shaking and then waiting and shaking again. Any ideas how to improve this? Change the focuser alltogether? Any options out there?

[CraigT82]

Is this the mirror moving focuser (knob on the back of the scope) or an aftermarket crayford/R&P focuser?

 

The skywatcher motor focus unit is cheap and can be fitted to all sorts of scopes with a little imagination, reduces vibration to nothing.  This is how I fitted one to a Skymax 150 I used to have...

 

[Alfian]

When you say shaking do you mean the image through the ep is shaking or that the focuser itself is somehow shaking? If its the first, what mount are you using? Higher power views which is what a mak is good for may give shaky views if the mount isn't adequate. In terms of the focuser stiffness, the SW 102 Mak I once had, had a "stiffer" focuser than the 4se mak that I have now but it had plenty of feel and was quite smooth in operation and gave no problems. If the focuset is stiff and feels to have a coarse action I would think there was a fault.

Edited November 12, 2018 by Alfian

[nightfisher]

It does sound like there is a problem with the focuser should not be hard to turn

[RT65CB-SWL]

If it still still under warranty, then I would return it to the vendor. If he/she refuses to play ball, then may I suggest an appointment with SCTelescopes if out of warranty.

My ETX105 primary started slipping a few years ago and found out that the primary mirror locking ring/collar needed tightening up. It may have come loose following a fall a few years earlier. A visit to SCTelescopes was done and the ETX105 collimated. 

Edited November 12, 2018 by Philip R

[heliumstar]

Guys, thanks for chiming in.

I was looking into motor focuser from SW but don't want to drill anywhere for now. The focuser itself ( original knob at the back ) doesn't shake in any way. It's just very stiff. Not like on other telescopes where it's light to move. I assumed Maks are kind of different and a little stiffer and you just have to live with it. I think the whole mirror moves with it in this design. The shaking I think is due to the mount. It's lightweight tripod that came with AZ GTI WiFi mount.

I am kind of reluctant to return this agan ( it was out of collimation ) since I am not really sure if it's an issue. It's just much stiffer than anything else. I can find focus but would be happier if it was easier. Might look into where I can mount that motor one.

[CraigT82]

I bought my mak 150 new and the factory focuser was stiff at first but loosened up over time.

There are a couple of screws on the side which are redundant and I attached the motor bracket using these, not sure if they are present on the smaller maks though

[Alfian]

One thought, assuming the focuser is stiff but still smooth. I think the rubber (?) coverered focuser knob is held fast on its shaft with a small allen bolt. Its possible that the knob is fouling the scope body making it stiff to turn. Slackening the allen bolt off and pulling the knob back a tad and retightening might do it. It might not but just an idea.

[heliumstar]

Thanks guys. Plenty of ideas to solve this. Will try loosening the knob first and if that doesn't work will think about how to mout the motor.

[NGC 2419]

On 12/11/2018 at 09:25, CraigT82 said:

Is this the mirror moving focuser (knob on the back of the scope) or an aftermarket crayford/R&P focuser?

 

The skywatcher motor focus unit is cheap and can be fitted to all sorts of scopes with a little imagination, reduces vibration to nothing.  This is how I fitted one to a Skymax 150 I used to have...

 

Do you have a link or a part number for this focus motor? Thanks.

[Merlin66]

I’m impressed with the versatility of the simple SW motor.

I’ve used it on the C9.25 and C11 as well as all my ED80 and TS102 as well as the spectroheliograph.

I use MXL 6mm toothed belts and 30 tooth pinions.

works 100% for me.

 

[CraigT82]

9 hours ago, NGC 2419 said:

Do you have a link or a part number for this focus motor? Thanks.

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/skywatcher-auto-focuser.html

 

I also needed to buy a toothed belt and pulley for this fitment but they're easily found online

[NGC 2419]

3 hours ago, CraigT82 said:

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/skywatcher-auto-focuser.html

 

I also needed to buy a toothed belt and pulley for this fitment but they're easily found online

Ah, thanks. No wonder I couldn't find it, I was looking for something that was belt driven. Looks like a Europe only item but I think the Orion USA one is identical.

 

Thanks again.

[catalinc]

Hello, 

And apologizing if a silly question: is it possible to remove the know of the internal focuser and so to create enough room on the backplate for installing a Crayford focuser (through a T2 to SCT adapter) ?

 

Thanks in advance.

[johninderby]

Big problem with that is that an SCT type crayford focuser only has a very limited focus travel. You still need the regular focuser.

[catalinc]

Ok, I understand, thanks for feedback.

Any chance to find a Crayford focuser with a smaller diameter,  to not collide with the internal focusing knob?

Or, would it be possible/feasible to add an extension tube btw. the telecope thread and the Crayford focuser, so to take the focuser out of the area where the collision with the knob occurs?

[JamesF]

42 minutes ago, catalinc said:

Hello, 

And apologizing if a silly question: is it possible to remove the know of the internal focuser and so to create enough room on the backplate for installing a Crayford focuser (through a T2 to SCT adapter) ?

This is also on the 102 Mak?

James

[catalinc]

Yes, my question was of course related to a SkyMax 102 (which I recently bought).

Sorry if it was not a clear question from my side.

[JamesF]

Just wanted to be sure, as once you get to the 127 for instance, there's room to fit an SCT-style secondary focuser without getting in the way of the main focuser knob.

James

[johninderby]

Pity Crawmach has stopped making 1.25” crayford focusers.