GSO linear bearing focuser slips with Quark and camera

[Ben Cartwright SASS]

I finally realized how while the GSO 10-1 Crayfords are good they really can't handle a load. I put the Quark and a cooled camera about 2 1/2 pounds total load on a focuser that is supposed to handle 9 pounds and while I can get the rough focus to work the 10-1 fine focus just slips no matter how I adjust the set screw, I can focus in past focus and then use the 10-1 to fine tune it coming out but it just slips trying to go the other way.

I noticed because the new Lunt ED102 with a 10-1 handles that load with no problem. I have a feeling it is a feather touch, not sure. But this is mostly when the scope is in a 50-80 degree up angle.

The GSO is on my SW ED100, I think John (lowjiber) has the same scope but not sure what he did if anything with the focuser.

I was wondering if a 2 or 2 1/2 inch feather touch or Moonlight would handle the load better?

[Bigzmey]

Obvious question, but did you tighten tension knob? I have the same issue with mine, unless I tighten it really tight.

[Gordon]

I finally realized how while the GSO 10-1 Crayfords are good they really can't handle a load. I put the Quark and a cooled camera about 2 1/2 pounds total load on a focuser that is supposed to handle 9 pounds and while I can get the rough focus to work the 10-1 fine focus just slips no matter how I adjust the set screw, I can focus in past focus and then use the 10-1 to fine tune it coming out but it just slips trying to go the other way.

I noticed because the new Lunt ED102 with a 10-1 handles that load with no problem. I have a feeling it is a feather touch, not sure. But this is mostly when the scope is in a 50-80 degree up angle.

The GSO is on my SW ED100, I think John (lowjiber) has the same scope but not sure what he did if anything with the focuser.

I was wondering if a 2 or 2 1/2 inch feather touch or Moonlight would handle the load better?

I had a GSO Crayford on my Newt. And I agree they tend to slip when they have any 'significant' weight on them. I fiddled and fiddled but never could get it to handle a 'cooled imager' or DSLR.

My Explore Scientific ED80 has a 10-1 rack and pinion. It works great and no slippage!

[Lowjiber]

The GSO is on my SW ED100, I think John (lowjiber) has the same scope but not sure what he did if anything with the focuser.

I was wondering if a 2 or 2 1/2 inch feather touch or Moonlight would handle the load better?

I do indeed have the GSO Linear Bearing Focuser on my SW ED100... Running the same equipment: Quark & ASI 174 Cooled cam.

I know this will sound crazy, but consider the source.

When I first installed the focuser, it would "slip" a bit under load and the sun fairly high in the summer sky. I disassembled the focuser and found it literally full of grease. I cleaned every moving part with alcohol and a bit of "elbow grease" and then applied a very tiny amount of SuperLube where needed.

After reassembly, I pulled the tube as far out as possible and gave it a good cleaning with alcohol and tightened the set screw tighter than normal.

It hasn't slipped since.

Regarding the Moonlite... I have one two-and-a-half inch focuser on another scope. If my Jeep ever gets stuck in the desert, I'll pull it out with the Moonlite.

[UlteriorModem]

Yep everything above is good advice. I too had to crank down my GSO. But I got it to work with a ASI180, filter wheel, oag, and sundry adaptors / rings.

If you do open it up there is a plastic 'bar' piece that goes under the shaft. Check that it is indeed there hasent been smooshed and clean.

[Ben Cartwright SASS]

If I tighten the tension knob beyond a gentle turn even the large focus wheel just turns and won't move the scope. I think I will take it apart and see if it needs degreasing

I will be posting picts from today from the Lunt ED102 the SW 100 and XLT120, what I found in just looking at the Astrostakkert sharpened shots (raw) that the Lunt ED102 and the XLT120 are very close in sharpness with very unstable air, that tells me that the lack of sharpness on the 120 1000mm scope is air turbulence especially at 11:30 am with the sun high in the sky and thin haze overhead. They both blew away the SW ED100 at this time. thread to follow tomorrow have to open the observatory (I am running the 16" meade for the public night tonight)

[Ben Cartwright SASS]

Oh BTW it is so nice to be able to type a reply and not worry about BBcode errors!

[Gordon]

Oh BTW it is so nice to be able to type a reply and not worry about BBcode errors!

wHAt bbCOde~~/=eRrors,>?

[Ben Cartwright SASS]

in Astro Forum if you typed the word scope in the groups it would give a BBcode error and you had to change it to $cope other words caused the same issue

[Bigzmey]

Again obvious thing, but large thumb screw on top is the focuser lock. One underneath is the tension screw.

[bobharmony]

I use the same focuser on my Newt with a DSLR-coma corrector hanging off it. After figuring out which is the tension screw and which is the lock screw, and getting them adjusted, I haven't had any trouble with the fine focuser, or slippage throughout a night of imaging.

Bob

[ab1963]

You could try the tweek by PolluxChung http://polluxchung.com/gso_crayford_fix/
I have done this myself to one i had attached to a SW ED100 and it made a world of difference but at the end of the day there is no match for a Feathertouch simply the best bar none,Hope this helps and if you do decide to have a go at tweeking the focuser and need any advice don't hesitate to contact me

[Ben Cartwright SASS]

You could try the tweek by PolluxChung http://polluxchung.com/gso_crayford_fix/
I have done this myself to one i had attached to a SW ED100 and it made a world of difference but at the end of the day there is no match for a Feathertouch simply the best bar none,Hope this helps and if you do decide to have a go at tweeking the focuser and need any advice don't hesitate to contact me

I will try the polluxchung fix and see if I break or fix the focuser. at the HO train club I am a running joke that I fix things with a hammer and duct tape (personally I now prefer Gorilla tape).

I find when the focuser is tensioned enough so it won't slip the fine focus won't lift the focuser up when it is at a 60-70 degree angle up. when it has less of a load I find that it has a smidge of backlash on the fine focus, ever so fine but is noticeable in the view on the screen. Even without load the fine focus (FF) will "snap" back from either direction not much but enough to be noticeable.

I keep thinking about a Feather Touch, just worry that it would be lipstick on a pig or putting fancy mag wheels on a Yugo with the XLT120, the SW ED100 would be a worthy scope. The 120 really isn't that bad but it does need good seeing to get good results. At the same time I have wasted money on stuff that doesn't matter and the FT would not be a waste.

[ab1963]

Similar problems to what i had Just do every step to the letter and you can't do more than that but hopefully when you are successful it will be twice the focuser What shocked me when i messed with mine is how little grease they put in with the bearings.

[Altocumulus]

Too much lubricant in the tube.....TMI

[Ben Cartwright SASS]

Just checked out the FT cost, $625 for the focuser and $225 for the adapter, $850! No way! I will tear the GSO apart and see what I can do, even if I destroy it, it is only $170 for a linear bearing focuser new! So if I mess it up it is 1/4 the cost of a FT

[Dyno05]

I have a solution that will probably work for you. My Astro tech refractor has what looks like a re branded GSO linear bearing focuser. Ever since I got the scope, used, I didn’t like the action. The fine speed would bounce back and I had to excessively tighten the adjustment screw. I took it all apart today. There were two issues. There is a nut inside for tensioning the ball bearing in the fine speed. If it’s too loose the fine speed will slip when you have a big load on the draw tube. Tightening it a little bit solved it for me. A very easy fix. The biggest gripe I had was that the focuser would spring back some when trying to achieve fine focus. It took me a while to figure that out. What it was is the knob on the left side of the focuser, opposite the fine control, does NOT fit snugly in its bore. It has play, so when you have a heavy load the shaft moves to and fro causing the spring back. I’m thinking of how to fit a beating on the shaft of knob to permanently fix it. For the time being. I put some tape in the shaft/ knob holder to take up the slop and greased the tape. The focuser works great now. Here’s a link to a quick video showing the play in the knob.

[Ben Cartwright SASS]

I will check it out

[Dyno05]

I will check it out

If your only issue was the fine adjustment won’t work but the coarse does, just tighten the internal but a tiny bit. It’s very easy to adjust. Remove the 4 screws holding the focus shaft assembly on the bottom, remove all the knobs. Slide the shaft out. Be careful not to misplace the plastic pressure brushing and the spacer underneath it. Tighten the nut a very little bit. Re assemble and test. You may have to do this a few times.
Hopefully this helps you. Maybe pack some new grease in the ball bearings while you’re there. Good luck.