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C11 Carbon Fiber VS Aluminum

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#1 Jefferson1964

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Posted 19 August 2004 - 04:21 PM

I noticed that the celestron 11GPS can be had for $2,995 and same model with carbon fiber is $3,500. Is there much difference in performance with the Aluminum or is this an old model maybe thats being cleared out. Saw this on Anacortas web site.....

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Posted 19 August 2004 - 04:56 PM

If you're doing astrophotography then the CF tube is the preferred choice otherwise save your money and grab the Aluminum tube.

The reason is that all OTAs contract to some degree and slowly lose focus as temperatures fall through the night. DSO astrophotography demands stable optical systems that don't lose their focus since you're looking at significant exposure times. Hence, since Carbon Fibre is thermally more stable than Aluminum, it is better able to hold focus for a longer period of time and reward you with pretty pinpoint star images 'a la APO' :smirk:


Cheers!
Rolly

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Posted 19 August 2004 - 08:42 PM

I almost bought the C11 CF tube and the CGE mount for like $4400 (with xlt), then I saw the "C11-SGT on CG-5 Mount - XLT Coatings" for $2279 -- I dropped my jaw and whipped out the ol' credit card in a flash (not really that fast, did some research and checking first).

The quality/stability of the mount with the C11 on top is iffy, but what a savings!$$$

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Posted 21 August 2004 - 09:20 PM

There is a guy selling a NexStar 11" XLT on a CF tube for $2000 or less (without tripod). Judge from the picture, it is a Faststar also. (a $200 extra option) There is another people selling a CGE tripod (without the EQ head) for $485 and it maybe able to modified to work on the NexStar.

http://www.astromart...ified_id=292251
http://www.astromart...ified_id=291892

#5 Jefferson1964

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Posted 21 August 2004 - 10:44 PM

Johan,

I appreciate the heads up and will be checking it out. Thanks, Jeff

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Posted 29 May 2005 - 02:27 PM

isn't carbon fiber also lighter than aluminum?if it is then the extra $$$ would go into increased stability much needed for astrophot. on budget mounts a la cg-5.

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Posted 29 May 2005 - 05:21 PM

All the Nexstar 11 GPS's have the carbon fiber tube, at least all the current models. My guess is that if you see one with an aluminum tube it's an older model. Or, are you sure it didn't say it was a 11" CPC with GPS? The new models from Celestron that are replacing the Nexstar GPS line are the CPC's and they all will use aluminum OTA's.

#8 Daniel Mounsey

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Posted 29 May 2005 - 08:06 PM

Thermally, the Aluminum is better than the CF for a closed system.

#9 Don W

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Posted 29 May 2005 - 08:17 PM

Celestron sold a number of NX11GPS scopes with aluminum tubes. Not all were carbon fiber.

#10 JerryWise

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Posted 29 May 2005 - 09:15 PM

This is prabably a rumor but it came from a dealer that called Celestron.

I am interested in taking a look at the 9.25 OTA. I had a Nexstar 8 GPS in Carbon Fiber and asked the dealer to order me a 9.25 in CF. He checked with Celestron and said they told him there would be no more Carbon Fiber tubes. I can't say if this is for the 9.25 or any/all of the line. This was about three weeks ago.

(By the way, just picked up a 9.25 with CG mount and accessories on EBay for 1,375 (Buy it now). It's 9 months old. Let's see how this transaction goes.) Here it is.

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Posted 30 May 2005 - 07:34 AM

Thermally, the Aluminum is better than the CF for a closed system.


Why? Wouldn't the aluminum retain heat, have a greater radiant (thermal curent) problem and flex with the cool-down more?

#12 JerryWise

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Posted 30 May 2005 - 12:23 PM

I can't quote figures on thermal coefficients but can compare the two.

I had a Carbon Fiber Nexstar 8 GPS I sold 2 months ago. After being without out it a month I picked up a C8 XLT OTA with Aluminum tube. The Carbon Fiber had very clear thermal current distortions in star test. Seemed to take forever to cool down. The aluminum OTA cools down very quickly. They are/were both kept in the same location inside and moved outside for viewing (of course). Temp differential was close to the same.

Again, it’s a heuristic observation with no controls.

The expansion control of Carbon Fiber is excellent. An OTA will not expand or contract much at all in Carbon Fiber which maintains critical focus during long exposures if the temperature drops. Aluminum though should cool down much quicker. However, Carbon Fiber when properly composed has some pretty good thermal characteristics too.

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Posted 30 May 2005 - 08:41 PM

I asked about the CF when I ordered my Advanced series and they would not allow the upgrade on it.

#14 Daniel Mounsey

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Posted 30 May 2005 - 09:48 PM

I can't quote figures on thermal coefficients but can compare the two.

I had a Carbon Fiber Nexstar 8 GPS I sold 2 months ago. After being without out it a month I picked up a C8 XLT OTA with Aluminum tube. The Carbon Fiber had very clear thermal current distortions in star test. Seemed to take forever to cool down. The aluminum OTA cools down very quickly. They are/were both kept in the same location inside and moved outside for viewing (of course). Temp differential was close to the same.

Again, it’s a heuristic observation with no controls.

The expansion control of Carbon Fiber is excellent. An OTA will not expand or contract much at all in Carbon Fiber which maintains critical focus during long exposures if the temperature drops. Aluminum though should cool down much quicker. However, Carbon Fiber when properly composed has some pretty good thermal characteristics too.


This is why I like the aluminum better.

#15 Powerstar888

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Posted 31 May 2005 - 01:14 AM

Cat Cooler is a great way to get those Carbon Fiber
scopes to cool fast.

I have one for my C-11.

Cat Cooler

#16 Daniel Mounsey

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Posted 31 May 2005 - 08:54 AM

We used one with CF and it's still a problem because once you pull it out the Cat 30 minutes later and the ambient temperature continues to drop, the tube can't fallow it. For CF, the Cat is a quick fix and that's it. I was so displeased with the thermal aspects of CF in closed tubes that I was literally getting stomped by my friends 5" D&G to the C9.25" I was testing. You could see the currents during the star test and it was pathetic to say the least. I just put the scope in the car since we were viewing planets. Some people may look through their CF tubes and think it's all great. Not where I view from, it's all relative. After yoiu look through a better scope, you don't wonna look through something worse.

#17 techmgr

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Posted 31 May 2005 - 11:26 AM

There is a global shortage of CF due to increasing demand (a lot of it military & mostly aerospace), and pricing is high. This may be why Celestron is making the new model with an aluminum tube.

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Posted 01 June 2005 - 12:39 AM

There is a global shortage of CF due to increasing demand (a lot of it military & mostly aerospace), and pricing is high. This may be why Celestron is making the new model with an aluminum tube.


Well that, plus their goal is obviously to make a more price competitive product than Meade and the CF isn't cheap. Not when compared to aluminum anyway. Should be really nice scopes though! I was going to wait and depending on reviews and how they seemed to be, go with the 11" CPC, but I just couldn't make myself wait til August. Will still be looking at them when they're out though!

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Posted 01 June 2005 - 01:10 AM

I can't quote figures on thermal coefficients but can compare the two.... I had a Carbon Fiber Nexstar 8 GPS I sold 2 months ago. After being without out it a month I picked up a C8 XLT OTA with Aluminum tube.


I can see where metal may cool quicker than carbon fiber. I have the CF tube, and use a Lymax Cat Cooler, but now that I think about it... the added flocking I have inside the OTA may also act as an insulator, further slowing cooling? :smirk:

All I can say is that 30 - 40 minutes with the cooler gets my scope in great viewing condition.

- Roger :cool:

#20 Steven

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Posted 03 June 2005 - 09:09 PM

There is a global shortage of CF due to increasing demand (a lot of it military & mostly aerospace), and pricing is high. This may be why Celestron is making the new model with an aluminum tube.


Where do Meade get their CF for the RCX series :question:

#21 techmgr

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Posted 04 June 2005 - 06:09 AM

There are only a very few producers of carbon fiber, and the bigger suppliers are adding capacity. It's a great example of supply and demand economics - pay enough and you can get some. And you can make a lot of RCX400's out of the same amount of carbon fiber that Boeing would use for a 7E7!! Meade is shipping RCX400's, but I think they're still in short supply. Maybe they're using the leftovers!! :lol:

#22 Jefferson1964

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Posted 29 June 2005 - 12:47 PM

How does a CAT cooler work? I know i need one for my SCT. I have been having trouble with my scope not cooling down as most times im viewing for short periods during weeknights. If im willing to let it sit outside an cool off until the wee hours its fine but then my beloved Jupiter is gone......

#23 Patrick

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Posted 29 June 2005 - 02:29 PM

How does a CAT cooler work?




See Here

Patrick

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Posted 07 July 2005 - 11:03 PM

I've owned both CF and Al versions of the 9.25.

Some points not mentioned...

The CF looks cooler than the Al and it stays pretty stable for focusing.

The CF is tougher than the Al - one accidental slight kick and I dented my Al scope. The CF will cool down just fine in my experience - HOWEVER, I did notice the Al cooled down quicker.

It's not a big deal to me.... yet.

#25 Bird

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Posted 07 July 2005 - 11:37 PM

Thermally, the Aluminum is better than the CF for a closed system.


Why? Wouldn't the aluminum retain heat, have a greater radiant (thermal curent) problem and flex with the cool-down more?


Aluminium conducts heat much better than CF, allowing the heat to escape from inside the OTA and mirror.

regards, Bird


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