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Synta Refractor Focuser Regreasing

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#1 AnthonyP

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Posted 17 July 2018 - 09:23 PM

When I got back into astronomy a few weeks ago I purchased a second hand Celestron Omni XLT 102mm refractor. It is a beautiful and wonderful scope. The only problem with the scope is the rack and pinion focuser being too sticky which made it difficult to focus in at higher powers.

 

Irj5GJQ.jpg

 

I cam across this post by SeaBee1: https://www.cloudyni...lems/?p=7023863 - It gave me the general idea of what to do. 

 

I decided to follow in his footsteps and show a step by step process of what I did to make the focuser more smooth.

 

The first step was the remove the focuser by removing three very simple screws:

 

CzLkWAN.jpg

 

HEFjRGd.jpg

 

I then turned the focuser over so it would be easier have access to the rack and pinion unit. I then removed the four screws that held the cover in place

 

FOP3Mv9.jpgMIby4Kn.jpg

FcG9o1R.jpg

 

With the cover exposed, a "spring" of sorts was sitting overtop the focuser wheel. I then took that out along with the focuser wheel

 

Fy2JBLW.jpg

 

7hAoSXm.jpg

meCGZ7H.jpg

 

It was easy at this point to slide out the focuser tube and separate all the pieces

 

pzzElF9.jpg


Edited by AnthonyP, 17 July 2018 - 09:24 PM.

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#2 vtornado

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Posted 17 July 2018 - 09:31 PM

Most excellent photos and step by step.   Do you do this for a living?

When you finish your project I will refer others to this link. 

Many are curious about re-lubing the focuser.

 

BTW that knob on the top of the focuser controls the friction on the draw tube.

If it is too tight, the focusing action will be rough.  If it is too loose, the focuser may

not stay where you leave it with a heavier eyepiece.  There is a butter zone.

 

There is also a butter zone for that plate that goes over the pinon gear too.

 

VT


Edited by vtornado, 17 July 2018 - 09:38 PM.

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#3 AnthonyP

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Posted 17 July 2018 - 09:35 PM

Once everything was disassembled, I took out a bottle of mineral spirits and white lithium grease. 

 

GyDyjlo.jpg

 

I do not have pictures of me doing the actual cleaning, but I poured a quarter of the mineral spirits into a tupperware pour and used a old toothbrush to wipe away all the grease. I was surprised at how quickly and easily the grease came off. With everything nice and clean I was ready to use the white lithium grease.

 

pzzElF9.jpg

 

I started by using paper towel to brush the grease on the teflon strips and housing for the focuser wheel

 

Z0k6pae.jpg

 

I then liberally applied grease to the focuser tube itself and put the focuser tube back in

 

DROq0np.jpg

 

gCGkBgH.jpg

 

PNJl7eL.jpg

 

I then put the focusing wheel back in with the "spring". I had put additional grease over this as well

 

zzLOAeV.jpg

 

Once all that was done I closed everything back up and reattached it to my telescope

 

gcd8DAv.jpg

 

Irj5GJQ.jpg

 

All in all this process took about 30 minutes and the focuser is smooth like butter now.

 

Next step is to take my CG-4  mount apart and regrease that smile.gif


Edited by AnthonyP, 17 July 2018 - 09:36 PM.


#4 AnthonyP

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Posted 17 July 2018 - 09:39 PM

Most excellent photos and step by step.   Do you do this for a living?

When you finish your project I will refer others to this link. 

Many are curious about re-lubing the focuser.

 

BTW that knob on the top of the focuser controls the friction on the draw tube.

If it is too tight, the focusing action will be rough.  If it is too loose, the focuser may

not stay where you leave it with a heavier eyepiece.  There is a butter zone.

 

VT

Glad you will put this to use. I do not do anything near this for a living. I work in sales. At first I was petrified to even do this, but I cannot stress enough how *simple* this was to do.

 

And yes, you're right about the butter zone. Part of finding that butter zone was to play around with that knob and with the four screws that hold the focusing mechanism together.


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#5 csrlice12

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Posted 17 July 2018 - 09:45 PM

WAY too much grease.....


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#6 AnthonyP

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Posted 17 July 2018 - 09:59 PM

WAY too much grease.....

I don't mind going back to fix this and lessen the grease, but what problems could occur if I left it as is?



#7 Chuck Z

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Posted 17 July 2018 - 10:07 PM

The excess grease on the drawtube has a way, in the dark, of migrating onto every surface that you don't want grease on. Especially optics shocked.gif . Just a very light application along the tracks where the drawtube slides on the tape will keep your focuser smooth. 

 

 


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#8 skytele

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Posted 17 July 2018 - 10:27 PM

In your third photo notice the two (2) small holes on top.  In each of those holes you will find a  recessed metric set screw.  Carefully tighten or loosen each set screw to further remove any focuser tube "play".  Metric Allen Key Size: 1.5mm (typically).  Before adjusting these set screws apply a drop of light oil in each hole.


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#9 skytele

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Posted 17 July 2018 - 10:43 PM

Remove the chrome Focuser Tube Lock Thumb Screw and look in its threaded hole.  You should see the black nylon miniature "puck" which contacts the Focuser Tube under pressure from the Thumb Screw.  A flashlight will help.  If you see the silver FT then you are missing the "puck".   The Thumb Screw must not come into direct contact with the FT or it will gouge it.


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#10 AnthonyP

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Posted 17 July 2018 - 11:17 PM

Remove the chrome Focuser Tube Lock Thumb Screw and look in its threaded hole. You should see the black nylon miniature "puck" which contacts the Focuser Tube under pressure from the Thumb Screw. A flashlight will help. If you see the silver FT then you are missing the "puck". The Thumb Screw must not come into direct contact with the FT or it will gouge it.


I just had a look. I do have the puck you refer to

#11 nicoledoula

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Posted 17 July 2018 - 11:24 PM

You didn't "re-grease" it. You removed the glue, then greased it for the first time. It was a grease virgin. 


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#12 nicoledoula

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Posted 17 July 2018 - 11:28 PM

No, use MORE grease, fill the tube with grease then poke a hole for light get through. It'll do better on planets like that. 60mm F/10 lol.gif



#13 SeaBee1

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Posted 18 July 2018 - 07:11 AM

Well... don't blame Anthony for the excess grease... If I remember correctly, when he asked me about my focuser refurb, I mistakenly told him to grease the tube, when I should have told him to grease the rack only. It has been a while back since I had done mine and I am going to blame old man memory for this one. crazy.gif

 

Anthony, I would definitely recommend taking it apart again and remove the grease from the tube. Grease migration onto optics would be a pain to remove... and that stuff will migrate...

 

 

CB, retreating now to humbly enjoy my pie...


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#14 Jon Isaacs

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Posted 18 July 2018 - 08:08 AM

In your third photo notice the two (2) small holes on top.  In each of those holes you will find a  recessed metric set screw.  Carefully tighten or loosen each set screw to further remove any focuser tube "play".  Metric Allen Key Size: 1.5mm (typically).  Before adjusting these set screws apply a drop of light oil in each hole.

waytogo.gif

 

I have reworked numerous Celestron, Orion and Skywatcher rack and pinion focusers..  They are all basically the same. 1.25 inch, 2 inch, refractor, reflector. Too many to remember.  Probably not 100 but maybe.  A few thoughts:

 

- The critical step is to adjust those set screws before installing the pinion gear.  You want it to be free of unwanted play but smooth and easy to move by hand. As they come from the factory,  these focusers are nearly always stiff but also shift because these little screws not properly adjusted.

 

- The next step is to install the pinion assembly.  I take time in adjusting the preload on the pinion so there is a minimum of backlash in the gear but the action is still easy.  Tightening the 4 screws until they bottom out results in an overly stiff focuser. I get the adjustment right and when I am happy with it out in the field, I will put a drop of crazy glue next to each screw head to lock it in place.

 

- If I use any grease at all, it is minimal, the pinion shaft and spring where it contacts the pinion shaft and occasionally I will lightly lube the drawtube but wipe it off before installation.  There is way too much grease in the photos. 

 

Grease and optics don't mix.  Invariably you will get the grease from the drawtube on your hands and it will find it's way to the eyepiece.  

 

- I just did an old Synta 120mm F/8.3 focuser yesterday.  To really make the focuser tight but smooth and easy, I replace the polymer strips with 0.015" bondable Teflon.  One side of the Teflon is etched so it can be glued. 

 

You can see the strips in this photo:

 

https://i.imgur.com/Z0k6pae.jpg

 

I just peel them off.  Sand the surface of the focuser to ensure a good bond.  I cut the strips about 0.60" wide and 3.0" long.  I just use "Crazy Glue Gel", spread out the glue on the etched surface, place the Teflon on the focuser and then use the drawtube with hand pressure to ensure a good bond.  Make sure the Teflon strip doesn't shift when installing the drawtube.  I do them one at a time. 

 

After about 5 minutes, I install the drawtube with the upper lock block, no grease. I adjust the two small set screws for the proper feel, smooth, light and no free play.  I then install the pinion as described above. 

 

I usually remove the focuser from the scope to avoid losing the upper focuser pad. So I will reinstall the focuser, and I am done. 

With the Teflon, the focuser is much lighter and very smooth.  It's not quite up the standard of my TeleVue rack and pinion focuser but it's surprisingly close.  I was getting real time focusing at 500x, no trial and error required.

 

I purchased the Teflon from Amazon.  It's a 6"x6"sheet.  Make sure you get the 0.015".  

 

https://www.amazon.c...f=biss_dp_t_asn

 

Jon Isaacs


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#15 AnthonyP

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Posted 18 July 2018 - 08:21 AM

Okay guys.... look forward to Part 2: Degreasing the "Degreasing". lol.gif


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#16 Jond105

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Posted 18 July 2018 - 08:34 AM

Good job man. I've done all my synta scope focusers as well that same way(minus the tube). I hope you do a play by play with the cg4 as you did here. Diving into my one and only mount to de-synta-glue it makes me a little nervous

#17 Exnihilo

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Posted 18 July 2018 - 10:19 AM

That's a lot of grease; mostly you just need it for the R&P and focusing axle itself; the teflon bearings smooth out the sliding of the drawtube.  But good job nevertheless, and great pics!


Edited by Exnihilo, 18 July 2018 - 10:19 AM.

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#18 jp071848

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Posted 18 July 2018 - 11:58 AM

Okay guys.... look forward to Part 2: Degreasing the "Degreasing". lol.gif

Hi Anthony...

 

There is some body of evidence to suggest that white lithium grease can separate over time into at least two different "substances" I've stopped using it years ago. I've had it turn into a grey-ish slime and a thin oily lubricant, and and this thin stuff tends to get into places where you don't necessarily want it to be.  When you do get your focuser de-greased, I personally would suggest you look into using a good Teflon/PTFE lubricant like Superlube, though it's not as widely available here in Canada. Canadian Tire do sell a similar Teflon lubricant in the auto section. I use these synthetic lubricants on all my mount and scope refurbs (most recently on my new Losmandy G11 and my trusty ES127 focuser overhaul). They work very well, stay where you put them, don't separate and, good for us Canucks, work very well in very cold temperatures.

 

Great photo essay BTW, I wish more of CN's "How To..." threads were as well documented. Good luck with your refurb.

 

Jeff


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#19 AnthonyP

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Posted 18 July 2018 - 08:33 PM

Part 2 - Degreasing and Regreasing

 

So I took everything apart again and used the minerals spirits to get all the excess grease off. I have included this time a photo of the cleaning of one of the parts. You will notice how white the mineral spirits liquid is from all the grease. Took me less than 10 minutes to get everything all clean

 

DV7qkiQ.jpg

910kr02.jpg

 

I then lightly greased all the parts that touch one another

 

V98Azee.jpg

f7rEtMU.jpgksAb9ud.jpg

XiMVEho.jpg

HUemo5P.jpg

 

I missed taking the photo of the "spring" (which was lightly greased) and the cover, but here we are.... all done with the excess grease all gone.

 

Irj5GJQ.jpg

 

Thanks for all of your input guys!


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#20 Jon Isaacs

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Posted 18 July 2018 - 09:10 PM

Anthony:

 

Very nice photos. 

 

I have to say this though:

 

I have gone through a great many of these focusers.  In my mind there are two important steps that you did not document:

 

- The adjustment of the two setscrews that adjust the play and smoothness/frictionof the drawtube.  This is best done prior to installing the pinion.  As received,  the drawtube is nearly always not properly adjusted , it's sloppy and yet manages to be too tight. 

 

It's worth spending a few minutes adjusting the setscrews so the drawtube has no freeplay and yet slides easily in the focuser. 

 

- Adjusting the pinion preload.  If you just tighten down the 4 screws that hold the pinion spring and gear in place,  the focuser with be stiffer than necessary . In general , i am able to find a sweet spot where there is no freeplay in the gear but the action is still light and easy .

 

Jon


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#21 Exnihilo

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Posted 19 July 2018 - 12:30 AM

Looking great, thanks for sharing!

#22 Steve Cox

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Posted 19 July 2018 - 05:02 PM

The excess grease on the drawtube has a way, in the dark, of migrating onto every surface that you don't want grease on. Especially optics shocked.gif . Just a very light application along the tracks where the drawtube slides on the tape will keep your focuser smooth. 

Better solution yet is to replace the two pieces of tape with pieces of actual teflon sheet, then the only grease you need is on the R&P gears, and best greases I've found to use are either Superlube, Pete's Red Synthetic, or if you have a supply or can still find it, IBM #23 typewriter grease.

 

The other thing about white lithium, is it is prone to separating, and especially in hot weather, running where it's not wanted, meaning as Chuck says, it'll eventually find its way to your eyepieces or such.



#23 AnthonyP

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Posted 20 July 2018 - 10:24 AM

Super lube it is. Part 3 this weekend....

#24 AnthonyP

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Posted 22 July 2018 - 01:39 PM

Part 3 - Regreasing with Superlube

 

I found Superlube at a local hardware store. $10.99 CAD for 3oz. Yowza.... 

 

2SwspG3.jpg

 

Here is the previously greased focuser with the white lithium grease still on it.... time to take this apart (3rd times a charm) and regrease it

 

ZHkVmuL.jpg

 

UQgtVXx.jpg

oXMa26y.jpg

 

Not showing the cleaning process, but here is everything all cleaned using mineral spirits and ready for Superlube

 

8CQT6LJ.jpg

 

Here is the focuser with the grease on the gear shaft. I also greased the plastic strips inside the focuser. I attemped to fix the "gibs" however the smallest allen key I had was 3/32" and that was still too big to adjust them. Does anyone know what size I should be using?

 

kRJZGIy.jpg

 

And the complete focuser regreased. I will say that it seems even smoother than the lithium grease I used earlier in the week.

 

Lastly, if you're hesitant to take the focuser apart, don't. Its very easy and as you can see from this post, I took it apart 3 times this week without an issue. If you have any questions, PM me.


Edited by AnthonyP, 22 July 2018 - 01:39 PM.

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#25 tony_spina

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Posted 22 July 2018 - 01:48 PM

If I recall you need a 1.5mm allen key


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