Tune Ups?

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GCoyote United States of America
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Tune Ups?

#1

Post by GCoyote »


Like a number other newbies, I have a few small used scopes that have decent glass on a less than decent mount/tripod. The advantage of that is I can do experiments on these to learn the ropes of telescope maintenance before I sink a lot of cash into a major upgrade. With that in mind, what tips/tricks/advice can some of you more experienced observers provide?

What are some common problems with inexpensive mounts and what can I reasonably do to fix them?
What do you do to increase stability?
What do you do to reduce the play in the mount?
Are there screws or knobs I should not replace with hardware store grade parts?

The weather is turning crappy(er) and my wife has some travel coming up so it's a good time to get out the tools and turn some screws before the clear winter skies I'm hoping for arrive.
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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Re: Tune Ups?

#2

Post by pakarinen »


Well, my TW 1 gets the shakes when focusing. There are several well-documented fixes - I'm going to try cutting a plate from Baltic birch for the arm.

In general though, I think adding / replacing bearings can help. Maybe add shims where / if needed. Replace the factory goo with a good lube.
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Lady Fraktor Slovakia
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Re: Tune Ups?

#3

Post by Lady Fraktor »


I do this for aluminium tripods: http://www.astronomyforum.net/blogs/gab ... ripod.html
For mounts I replace the soft, poorly machined and plated hardware with stainless steel.
Checking tolerances to help stabilize the mount you can use PTFE sheets to fill any gaps to get rid of the wobble in them.
Taking the mount apart and smoothing out any rough contact ares helps as well.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
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Re: Tune Ups?

#4

Post by helicon »


You can also hang a weight or sand bag from the mount/tripod to improve firmness. A cheap fix that will help prevent the shakiness associated with underwhelming mounts.
-Michael
Refractors: ES AR152 f/6.5 Achromat on Twilight II, Celestron 102mm XLT f/9.8 on Celestron Heavy Duty Alt Az mount, KOWA 90mm spotting scope
Binoculars: Celestron SkyMaster 15x70, Bushnell 10x50
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Re: Tune Ups?

#5

Post by GCoyote »


Good info. One of the cheaper mounts is clearly a casting with a poor connection to the tripod. Definitely will try to insert some material between the two to solidify the rig.
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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gregl
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Re: Tune Ups?

#6

Post by gregl »


It's hard to be specific as there are many problems that arise. Correcting poor machining can be simply a matter of cleaning up the fit, or can be as major as re-machining or making a new part. Be sure to check any lubricated parts and consider replacing the original lube with something better. I find the grease used on Asian goods to be sticky and sometimes a bit dry or even contaminated. Lithium grease works well but don't overdo it. Oil often looks like used engine oil; I'd replace that. OTOH some areas should not have lube; you just have to use your judgment on that. I've also seen cases where thick grease was used to compensate for sloppy machining. As Michael writes above, adding weight to the rig helps. Sometimes just replacing a cheap tripod is the better option — there is no substitute for a good heavy one.

For any setscrews or knobs that use the end of the threaded screw to seat against a part to be secured, check the end of the screw and round it off if needed. Frequently the screws have a burr or ridge around the end of the thread that will dig into the part it is supposed to secure. Sometimes putting a bit of brass, copper wire or plastic in the hole first is a better option.

The screw on the left has a burr around the end of the thread. The one on the right has been smoothed down on the belt sander.
IMG_8080.JPG


The locking mechanisms on tripod legs always give me pause. Some just don't inspire confidence, and I have had visions of a scope taking a tumble when a leg telescopes down accidentally. For those, I have used shaft collars (from an industrial supply such as McMaster Carr) or bicycle seat clamps secured to the smaller leg and set up against the larger one. Below are a couple of pix of some bike seat clamps on the legs of an old Celestron tripod. The bike clamps have a ridge on the i.d. that needs to be machined or filed off so they'll seat against the leg tube. Shaft collars don't have that but then you'll need an Allen wrench to tighten them. Although you could swap out one of the Allen screws for a T-knob.


A bike seat clamp on the leg of an old Celestron tripod:
IMG_8078.JPG
IMG_8079.JPG


Shaft collar, avail. at industrial supply sources:
external-content.duckduckgo.jpg
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Re: Tune Ups?

#7

Post by GCoyote »


Excellent! Just the sort of tips/tricks I'm looking for.
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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