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Tube rings - how tight should they be?

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14 replies to this topic

#1 Bkmiller4463

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Posted 25 November 2021 - 02:58 PM

I realize this is subjective, but how do you decide when your OTA is held securely by the rings?There is such a range between ‘closed’ and ‘over-tight’ that makes me wonder, so I make them just tight enough so I can’t easy rotate the tube. Is that tight enough?


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#2 Cygnus0629

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Posted 25 November 2021 - 03:01 PM

I usually tighten them just enough so the OTA won’t slide freely and I can spin the tube pretty easily.

I leave it on the mount inside my house and I usually tighten it more when it’s inside…but I don’t really crank it down either.

I know it probably wouldn’t happen, but I’ve had horrible visions of denting my refractor because I over tightened the rings lol

Edited by Cygnus0629, 25 November 2021 - 03:20 PM.

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#3 ris242

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Posted 25 November 2021 - 03:33 PM

>>I realize this is subjective

 

yes.......so I'd say - just enough.

 

I've never had any issues in this respect..............more issues with mounting the scope/plate onto the mount!!

 

Some poorly made rings don't have a large gap to start with - you tighten down and they contact each other. If that is an issue add a bit of felt to increase the gap. The other issue I have had is the threads can be a little short.

 

When clamped you could also check - before picking up the unit - put your finger between the scope and the screw and see if you can push it off its secured position..........if so its too loose.

 

 

[  The Stellarvue rings I have on the 5" have such a stiff back hinge, huge knurled screws, long threads, a decent PTFE washer and a 1/4" gap............finger tight is good enough........its not going anywhere   ]


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#4 Bkmiller4463

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Posted 25 November 2021 - 03:34 PM

Me too! I’d have to send it back to Stellarvue for repairs, accompanied by a “the dog must’ve done it” excuse. 

 

Thanks for the reply. 
 

I usually tighten them just enough so the OTA won’t slide freely and I can spin the tube pretty easily.

I leave it on the mount inside my house and I usually tighten it more when it’s inside…but I don’t really crank it down either.

I know it probably wouldn’t happen, but I’ve had horrible visions of denting my refractor because I over tightened the rings lol


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#5 pyrasanth

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Posted 25 November 2021 - 03:35 PM

This is a very relevant topic for me. I recently tried to respace my tube rings on my C14. The thinking was to move the mount versa plate as far forward as possible and put the rings closer together. This was to aid balance in declination. However the rings being very close together did not adequately support the very back end of the telescope so before locking the top rings in place gravity tilted the tube. I thought that by brute force and tightening the top rings this would hold the tube straight and parallel. I was wrong- the pressure effectively "bent" the optical path and the stars looked like comets all over the field.

 

It was only when I undid the change that the stars returned to normal however I had considerable trouble getting the mirror locks to loosen even when returning to the original configuration. When the locks were finally released I heard a light twang as the primary mirror settled back into its normal position.

 

This proved, at least to me, that it is possible for rings to be too tight thus causing distortion to the optical path. Snug is good however tight might be a little in the wrong direction. This probably would not have happened with Parallax rings as they are a hinged assembly however the Bisque rings are in sections and if any section is tilted then the problem can occurr.


Edited by pyrasanth, 25 November 2021 - 03:37 PM.

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#6 Couder

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Posted 25 November 2021 - 04:15 PM

I use my brass refractors on a mount, I thought I had them tight. They were still sliding when they were close to vertical, so even though I could not turn (rotate) them by hand they were too loose. I ended up adding another layer of felt.



#7 Bkmiller4463

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Posted 25 November 2021 - 05:52 PM

Good tip, thanks! I noticed the same about the Stellarvue rings being stiff and substantial. That’s part of the reason for my post - it seems as though they’re overbuilt and will hold anything, so ‘just tight enough’ is the rule. 
 

 

When clamped you could also check - before picking up the unit - put your finger between the scope and the screw and see if you can push it off its secured position..........if so its too loose.

 

[  The Stellarvue rings I have on the 5" have such a stiff back hinge, huge knurled screws, long threads, a decent PTFE washer and a 1/4" gap............finger tight is good enough........its not going anywhere   ]



#8 teashea

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Posted 25 November 2021 - 06:06 PM

I realize this is subjective, but how do you decide when your OTA is held securely by the rings?There is such a range between ‘closed’ and ‘over-tight’ that makes me wonder, so I make them just tight enough so I can’t easy rotate the tube. Is that tight enough?

yes   you got it


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#9 Jon Isaacs

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Posted 25 November 2021 - 09:58 PM

Good tip, thanks! I noticed the same about the Stellarvue rings being stiff and substantial. That’s part of the reason for my post - it seems as though they’re overbuilt and will hold anything, so ‘just tight enough’ is the rule. 
 

They're essentially the same rings as many other scopes use.  They are tightened by hand so its not really possible to overtighten them. 

 

I'm using alt-az mounts so I tighten the rings quite tight, tight enough that there's no way they'll slide or rotate.

 

Jon



#10 Bkmiller4463

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Posted 25 November 2021 - 11:05 PM

Thanks Jon. I'm curious - why would they need to be tighter with an alt-az mount vs a GEM? I ask because I am considering an alt-az for the SVX140.

 

 

They're essentially the same rings as many other scopes use.  They are tightened by hand so its not really possible to overtighten them. 

 

I'm using alt-az mounts so I tighten the rings quite tight, tight enough that there's no way they'll slide or rotate.

 

Jon



#11 PKDfan

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Posted 25 November 2021 - 11:28 PM

I recently had issues with getting all the vibration weak points on my rig minimized including tightening my tube rings so they reach that perfect tightness without going past.

 

Like torquing a head bolt or lug nut properly.

 

I think it helped a bit to further dampen vibes past the merely snug level I had before.

 

 

 

Clear skies & Good seeing


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#12 Jon Isaacs

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Posted 26 November 2021 - 01:10 AM

Thanks Jon. I'm curious - why would they need to be tighter with an alt-az mount vs a GEM? I ask because I am considering an alt-az for the SVX140.

 

With an EQ mount, you might want to rotate the tube, it might be one iota easier if the rings weren't quite so tight.

 

With an Alt-az mount, there is no reason to rotate or slide the tube once it is properly positioned so just tighten them up.

 

Jon 


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#13 Sketcher

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Posted 26 November 2021 - 06:41 PM

It kinda looks like different people have different opinions and/or different concerns on this topic.

 

For the three refractors I have that get mounted in rings (objectives of 80mm, 130mm, and 152mm) I tighten the rings very firmly, but without the use of tools.  My OTAs are all solid enough, and their corresponding rings fit well enough that I have absolutely no concerns about denting an OTA.  Basically I go pretty much as tight as I can using my fingers to tighten the hand nuts.  I don't want my OTAs sliding lengh-wise nor rotating within their rings without first having to loosen the rings.

 

As for keeping the rings loose enough to be able to rotate the OTA within their rings on an EQ mount:  For the way I use my equatorially mounted telescopes, I find it better to keep the OTAs firmly "locked" in their rings.

 

Two of my OTAs pretty much permanently stay in their rings regardless of whether they're attached to their mounts or not.  (My 130mm scope doesn't easily fit in its case with rings attached.)  It's very rare for me to feel any need to rotate my OTAs within their rings.  Perhaps my observing habits/style are a factor here.

 

I tend to concentrate my observations near the meridian that runs from the north celestial pole to my south horizon.  Furthermore, I tend to take my time to "seriously" observe only a few objects per session, sometimes only one object.  So I'm not needing to swing my OTAs around to widely different parts of the sky during any one session.  In other words, my finders very rarely end up in widely different positions during any one observing session.

 

I suppose if one's observing style involves checking out objects in widely different sky regions during a single observing session (and perhaps not spending much time on any one object) then one might be more concerned about easy OTA rotation.  But for me and my ways, that's not a problem that I have.  So I keep the rings tightly "clamped" to my OTAs.  Besides, my scopes go back into their cases better if they don't get moved around within their rings.

 

We don't all do things in the same way.  So we don't all experience the same problems -- even when using the same equipment.

 

If my OTAs were less solid, and/or if my rings didn't fit my OTAs as well, then yeah, I would want to be more careful about how much I tighten the rings.  As usual, details are going to vary from telescope to telescope, from rings to rings, from individual to individual, and yes, even with one's observing habits.

 

Find out what works best for you, your equipment, etc. and go with that.  Following the practices of others won't always work well for everyone else.


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#14 daquad

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Posted 26 November 2021 - 08:12 PM

I tighten the rings until the tube can neither slide nor rotate.  One time when I was trying to balance the mount I would tighten the rings only a bit, because I knew I would have to move the scope again.  After I had the scope balanced I forgot to tighten the rings further.

 

I then proceeded to align the mount to the pole, because I like to use setting circles to find difficult objects. I soon discovered, after several attempts to find M34 that I was a degree or two off the mark.  I later realized that although the scope could not slide in the rings nor be rotated, it did shift in the rings at different positions.  

 

I retightened the rings and redid the polar alignment and the issue was solved.

 

So I tighten the rings until the scope can neither slide nor rotate and the take another turn on the screws to make sure the tube cannot shift when in different positions.

 

Dom Q.


Edited by daquad, 27 November 2021 - 09:57 AM.

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#15 barbie

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Posted 26 November 2021 - 10:19 PM

I keep the tube rings just tight enough so that the tube can't slide or rotate. If using slightly oversized rings, simply add some felt to the I.D. of the rings until they hold the tube securely but not overly tight.


Edited by barbie, 26 November 2021 - 10:21 PM.

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