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TEMP-est Fans for non-Edge HD Scopes

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#1 iam1ru12

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Posted 30 April 2015 - 08:53 PM

Hello All,

I'm wondering if anyone has installed the "TEMP-est TEMPerature Equilibration System for Telescopes - For Retrofitted Telescopes" which is basically Deep Space Products option for scopes that do not have the passive vents from the factory like the EdgeHD and some newer Celestron SCTs.  Here is a link to the actual product: http://www.deepspace..._4243_9336.html.

 

Part of installation process is cutting 2 round openings in the rear of the OAT.  While I'm a pretty handy person, the thought of opening up my CPC1100, removing the mirror and cutting a hole in the back does give me pause.  As anyone here installed these themselves or performed a similar upgrade?  Any pictures or information you can share?

 

I'd have Deep Space Products do the procedure for me by they are in Arizona and I'm in North Carolina.  I won't ship my OTA.

 

Thanks!

-Mike



#2 HenryB

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Posted 01 May 2015 - 06:03 AM

Great question! I have contemplated doing this to my C11 OTA because the difference in the view without a heat plume is amazing. I use an SCT cooler before a viewing session and it helps for a while, but here in NC we often get significant temperature drops after sunset so continuous cooling is necessary. The best views I get are the rare nights without the large temperature drop so it is clear what is needed. I have disassembled the OTA before but drilling large holes in cast aluminum causes me worry about structural integrity. It would be nice to hear the experiences of others that tried this.

 

Bryan



#3 junomike

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Posted 01 May 2015 - 06:33 AM

I also considered going this route, but I'm leary of all the necessary disassembly required.

Ed will do the "mod" for you if you send in the OTA I believe, but I Imagine it will be pricey due to labor required.

 

Mike



#4 iam1ru12

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Posted 01 May 2015 - 08:13 AM

I also considered going this route, but I'm leary of all the necessary disassembly required.

Ed will do the "mod" for you if you send in the OTA I believe, but I Imagine it will be pricey due to labor required.

 

Mike

 

Mike,

i'm more worried about potential damage in shipping (though I have all of the original boxes) than I am in me screwing up or damaging something if I install the fans myself.

 

-Mike



#5 macdonjh

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Posted 01 May 2015 - 08:14 AM

I didn't install the TEMPest fans, but I did install two 60mm fans in my C11.  It's not really that hard to do, but it takes time.

 

Disassembly of a Celestron SCT isn't all that difficult.  The biggest problem is if this is the first time the scope has been disassembled, the tube is hard to separate from the rear casting.  I had to use a wood block and a hammer to tap the pieces apart when I disassembled my scope.  The steps are:

 

-  Remove the corrector plate and secondary mirror assembly.  Be sure to mark the orientation of the corrector plate, there's only one right way to put it back.  They are typically marked at the 3:00 position (when looking at the front of the scope) by Celestron at the factory, but don't take a chance, make your own mark.

-  Remove the focuser knob and then the bearings from the back of the scope.

-  Reach into the OTA and remove the snap ring that acts as a safety stop to prevent the primary mirror from sliding off the end of the baffle tube.

-  Screw the focuser shaft until the primary mirror disengages from the shaft.  You can now slide the primary mirror assembly off the baffle tube and out of the OTA.

-  Put all your glass parts in a safe, protected place while you play with the metal bits.

 

There are threads out there (Astromart, the C14 Yahoo group, and here I'm sure) about disassembling SCTs.  You can get more details and more cautions there.  As I said, it's pretty simple, but there are things to watch out for (sticking corrector plates, corrector plate orientation, grease on the baffle tube, out gassing, etc.).  There are also other things you can do while you have the scope apart (cleaning and regreasing the baffle tube, cleaning the primary, secondary and corrector, flocking, etc.).

 

The rear casting is aluminum and can be worked using wood tools.  Really.  I used regular drill bits and a hole saw to make the cuts required in my rear cell.  Once the fans, switches and wiring were installed, I cleaned out any debris and reassembled the scope.  A few minutes' collimation and I was back in business.  Of all the modifications I made to my C11, the fans were tied with the internal dew heater for the best and most effective.



#6 MDavid

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Posted 01 May 2015 - 09:10 AM

...internal dew heater ...

 

Internal dew heater? Not to hijack but huh? where'd you put that?



#7 EFT

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Posted 02 May 2015 - 01:11 AM

Installing the TEMP-est retrofit fans or anything similar is not a job that I recommend for many people.  It's the worst job in the world, but it certain has the potential for doing damage if you are not VERY careful when pulling out the optics.  In addition, it is messy.  There is often enough grease in there to lube 20 scopes and all of that has to be cleaned out so that you don't end up with aluminum shavings in it and then replaced when you are done.  I have done it for a number of people and did it in conjunction with a scope HyperTune (which I am not currently offering) since installing the fans involved doing everything that I would have to do in a HyperTune anyways.  I do still work with people to do it though. 

 

Structural integrity is not an issue at all.  There are ribs inside the back of the OTA and the fans holes are drilled in between those ribs and are only 1-3/8" in diameter (big fans are definitely not necessary).  Bi-metal holes saws from the local hardware store work great.  A large drill press can make things easier.  C11 and C14 OTAs can easily hold 4 fans.  C8 and C9.25 can hold 2 or 3 fans. 

 

As far as shipping goes, I have not lost an OTA yet (I'm knocking on wood right now).  But shipping them, particularly the larger ones always worries me.  The trick is to photograph the optics before packing, use the original packing materials, pack very carefully, and insure for full replacement value.  However, shipping an entire CPC11 would start to get very costly.



#8 Jae

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Posted 02 May 2015 - 04:59 AM

Hi Ed,

A question I have is, which is the more effective cooling? Assuming same optics, an older
OTA with these fans or just buying a new one and adding the fans to existing holes?

The best may be to have a new ota retrofitted with both types of cooling? Or is the purchase of a newer ota not necessary as the retrofit is the more effective ? Just to make sure if $$ are not the issue, just do both to get the best of both worlds?

Thanks!

Jae

#9 EFT

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Posted 02 May 2015 - 10:42 AM

The retrofit vents use 25mm fans while the vents for the EdgeHD 8 and 9.25 use 17mm fans, the 11 uses 25mm fans and the 14 uses 20mm fans.  This is dictated by the size of the original vents.  However, even the two 20mm fans used in the C14 EdgeHD are sufficient to do the job.  One thing people tend to not thing about is the actual volume of air that needs to be exchanged as opposed to the flow rate.  Very small fans can do the job just fine by themselves.  40mm computer fans are way overkill.  Comparing a C8 with two 25mm fans vs. a C8 EdgeHD with 17mm fans might show you a slightly faster initial cool down, but it is not extremely significant even though the CFM of the 17mm fan is half that of the 25mm.  What is more important than initial cool down is keeping the temperature in line with the ambient temperature.  That is actually the primary purpose of the vent fans and all you need for that are very small fans.  If you really need faster cool down, then you can put an additional fan in the Fastar hole of the EdgeHD scopes and then remove it when you start to view/image.

 

So in answer to the question, if you don't want to dissect and SCT, then the best way to go is with a new SCT that already has vents in it.  Beyond that, it really doesn't matter.  But I would never bother to install both vent fans and retrofit fans in an EdgeHD scope.



#10 Jae

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Posted 04 May 2015 - 03:46 PM

Thanks Ed !



#11 junomike

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Posted 05 May 2015 - 02:18 PM

The retrofit vents use 25mm fans while the vents for the EdgeHD 8 and 9.25 use 17mm fans, the 11 uses 25mm fans and the 14 uses 20mm fans.  This is dictated by the size of the original vents.  However, even the two 20mm fans used in the C14 EdgeHD are sufficient to do the job.  One thing people tend to not thing about is the actual volume of air that needs to be exchanged as opposed to the flow rate.  Very small fans can do the job just fine by themselves.  40mm computer fans are way overkill.  Comparing a C8 with two 25mm fans vs. a C8 EdgeHD with 17mm fans might show you a slightly faster initial cool down, but it is not extremely significant even though the CFM of the 17mm fan is half that of the 25mm.  What is more important than initial cool down is keeping the temperature in line with the ambient temperature.  That is actually the primary purpose of the vent fans and all you need for that are very small fans.  If you really need faster cool down, then you can put an additional fan in the Fastar hole of the EdgeHD scopes and then remove it when you start to view/image.

 

So in answer to the question, if you don't want to dissect and SCT, then the best way to go is with a new SCT that already has vents in it.  Beyond that, it really doesn't matter.  But I would never bother to install both vent fans and retrofit fans in an EdgeHD scope.

Ed, Even though the 20mm is sufficient for the C14, why are they made smaller than the one's on the  C11?

 

Mike



#12 EFT

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Posted 05 May 2015 - 02:42 PM

Certainly one of my greater frustrations.  When I first went to work on designing the TEMP-est for the C14HD I assumed that the 25mm fans would fit since they fit in the C11HD.  But the holes for the vents in the C14HD are slightly more narrow than those in the C11HD.  As a result, there was no way to fit the 25mm fans and I had to switch to the 20mm.  I didn't have a C14HD on site when I was designing the TEMP-est for them, I just had the vent covers.  I ended up driving about 40 miles each way to the customer's house numerous times in order to get the right fit.  I didn't design the C9.25HD TEMP-est until I had one in house I could work on.  It's the same issue between the C8HD and the C9.25 HD.  You would think that the C9.25 could hold a larger fan than the C8HD, but while the C9.25HD vents are longer, they are just as narrow as the C8HD vents.



#13 junomike

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Posted 05 May 2015 - 07:29 PM

Ah, so they are longer but not as high! 

Thanks for the explanation as I couldn't understand the theory behind it.

 

Mike




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