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Optimum thickness of felt in telescope rings

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#1 druhela

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Posted 31 October 2020 - 01:10 AM

I feel the 'stock felt' on my GSO rings is too thin (around 1-1.5 mm) (also, not properly applied to ring joints; and the rings in general also feel tight to rotate the OTA around on the EQ mount), which is scratching the paint off my OTA. 

 

IMG_20201031_113139~2.jpg

 

Wanted to reline the inside of the rings myself. Many thickness options are available (both in wool & synthetic felt) which is confusing.

 

Some of the standard sizes that I've seen being used/ sold online:

 

1/8" ~ 3.175 mm
3/16" ~ 4.7625 mm

1/4" ~ 6.35 mm

 

Can anyone suggest the thickness of felt they are using in general which works for them? 


Edited by druhela, 31 October 2020 - 01:12 AM.


#2 endlessky

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Posted 31 October 2020 - 02:15 AM

If this is just for visual purposes, I don't think it would matter much. Maybe I would get the 3/16" ones, and cut them a little larger than the width of the ring itself.

 

I say this because with astrophotography you also experience something such as differential flexure (if you use a guide-scope) and the more things can flex/deform, the worse it is. In this case, the thicker felts would make things worse, as they will deform more under weight.


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#3 druhela

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Posted 31 October 2020 - 02:30 AM

If this is just for visual purposes, I don't think it would matter much. Maybe I would get the 3/16" ones, and cut them a little larger than the width of the ring itself.

 

I say this because with astrophotography you also experience something such as differential flexure (if you use a guide-scope) and the more things can flex/deform, the worse it is. In this case, the thicker felts would make things worse, as they will deform more under weight.

Thanks! This is indeed for visual purposes only. 


Edited by druhela, 31 October 2020 - 02:30 AM.


#4 DLuders

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Posted 31 October 2020 - 03:20 AM

ScopeStuff has Felt Strips for Ring Padding in various thicknesses.  If in doubt, you can get a slightly-thicker one and shave it with a razor blade for a custom fit.  smile.gif


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#5 BillB9430

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Posted 31 October 2020 - 09:44 AM

Druhela - adhesive backed firm wool felt strips of width 1/2", 1", 1.5", and 2" with thicknesses of 1/16", 1/8", 3/16", 1/4", 3/8", and 1/2" are available in ten foot lengths from McMaster-Carr. Perhaps similar are available in India?

 

I've attached these strips and thinned them with a sanding drum to get a precise fit on the OUTSIDE of the sliding coarse focus module for my Jaegers 5" RFT (see attached views from April 2, 2020 LDSF post), but it is even easier to apply to the INSIDE of rings and then gradually thin the felt liner thickness with the sanding drum to get just the right tension on your scope tube. Hope this helps. - Bill

 

Photo 20 copy.jpg  Photo 28.  copy.jpg


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#6 druhela

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Posted 31 October 2020 - 10:07 AM

Druhela - adhesive backed firm wool felt strips of width 1/2", 1", 1.5", and 2" with thicknesses of 1/16", 1/8", 3/16", 1/4", 3/8", and 1/2" are available in ten foot lengths from McMaster-Carr. Perhaps similar are available in India?

 

I've attached these strips and thinned them with a sanding drum to get a precise fit on the OUTSIDE of the sliding coarse focus module for my Jaegers 5" RFT (see attached views from April 2, 2020 LDSF post), but it is even easier to apply to the INSIDE of rings and then gradually thin the felt liner thickness with the sanding drum to get just the right tension on your scope tube. Hope this helps. - Bill

 

attachicon.gifPhoto 20 copy.jpg  attachicon.gifPhoto 28. copy.jpg

The sanding drum idea is very convincing. I have contacted a supplier here in India who'd be sending me 4 mm thick sheets. Would use the sanding drum, if required to get a snug fit. Thanks for the help! 



#7 druhela

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Posted 31 October 2020 - 10:11 AM

ScopeStuff has Felt Strips for Ring Padding in various thicknesses.  If in doubt, you can get a slightly-thicker one and shave it with a razor blade for a custom fit.  smile.gif

I like how they've used the thick strips of felt to cover the pinned joint region in the sample photo. They've eliminated all contact, without compromising on movement of the hinges. 

 

Fotor_160415726765010.jpg

 

However, the GSO rings are a bit different from the ones shown. I'd try to leave some felt over the hinges without sticking it in that region. 


Edited by druhela, 31 October 2020 - 10:19 AM.



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