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Carbon fiber tubes - good idea?

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#1 hawkman

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Posted 19 October 2019 - 06:25 PM

I'm getting back in to astronomy and am on the hunt for a 10" or 11" scope.  I periodically see some for sale with carbon fiber tubes.  I somewhere got the impression that these are not a good idea as they extend the time it takes for the scope to reach thermal equilibrium.  Is that the case?  Anyone with experience with these scopes.

Thanks very much.

John Hawkins

Napa Valley, CA



#2 fcathell

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Posted 19 October 2019 - 06:33 PM

I think they are good for open tube scopes like Newtonians and classic Cassegrains,  but not a good idea for closed tubes like SCTs, refractors, and Maks.

 

Frank


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#3 Dynan

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Posted 19 October 2019 - 07:11 PM

I love how my Explore Scientific ED127CF holds focus. Even with the hard temperature swings in the summer months down South, it held focus even though I check it periodically. I have run over three hour sessions and still had focus when checked with a Bhatinov mask. YMMV.


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#4 AhBok

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Posted 19 October 2019 - 07:47 PM

My CF 8” F4 newt equalizes in about an hour and then holds focus with about 3 microns inward travel per degree C. This is easily managed with my temp compensated autofocuser. One caveat: when I first got the scope, I mounted D plates on top and bottom. This gave me fits trying to figure out temp compensation since the big aluminum plates have a different thermal expansion characteristic. Got rid of them and temp compensation is easy and reliable. Lesson learned. If I ever decide I need upper and lower D plates, I may as well save a few bucks and go with a metal tube.
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#5 Paul Hyndman

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Posted 19 October 2019 - 08:08 PM

There are trade offs, but carbon fiber tubes have been quite successfully integrated in many high-end designs. The 10" AP MCT is such an example:

 

"We have redesigned the mechanical and optical parts of this telescope to make it lighter weight and to enhance the performance
even in falling temperatures. Weight was reduced two ways: the tube is now carbon fiber and the optics are substantially thinner and
lighter weight than the original. The thinner optical components retain much less heat, which allows faster cool down. We are still
using fused silica quartz for the mirror and high quality crown glass for the corrector"

 

 

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#6 stevew

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Posted 20 October 2019 - 03:08 PM

Years ago I had a C/F C9.25. It took forever to reach thermal equilibrium. 

A Lymax CAT cooler helped a lot, but I'd never buy another C/F tube telescope.



#7 junomike

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Posted 20 October 2019 - 03:59 PM

Having owned a CF C11 for almost 10 yrs I can tell you I find the pros outweigh the cons.

It does take more time to acclimate but it also suffers less from temperature fluctuation and is more Dew resistant then

the Al tubes.  It's also marginally lighter and is less prone to scratches and nicks.


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#8 Bean614

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Posted 21 October 2019 - 06:20 PM

I will have to take the opposing view.

     If  you're going to insulate the tube with Reflectix, CF is the absolute ideal material for an SCT!  Since the insulation reduces the amount of cooling, thus eliminating most thermals, the CF only enhances this, as it cools slower.

   If you're not familiar with this, just enter "Insulation" in the Search Window, and start reading.

   All my NexStar GPS Scopes (8, 9.25, and 11) had it, and I was viewing with perfect images as soon as my alignment was complete.



#9 Jason B

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Posted 21 October 2019 - 08:23 PM

My 8" RC is CF and in an observatory. No issues, holds focus all night though Michigan is not known for drastic temp changes other than some nights in the fall.

I think open tube or observatory really highlight the benefits of a CF tube...
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