How big of a difference have you noticed with cooling your telescope mirror?

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Discussion Overview

The discussion revolves around the impact of cooling telescope mirrors on image quality, particularly in the context of a C11 telescope. Participants explore various methods for cooling, including the use of fans, thermoelectric coolers, and pre-cooling strategies, while considering the implications of modifying the telescope's structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the effectiveness of cooling a telescope mirror for improving image quality, specifically in a C11 model.
  • Another participant suggests that cooling is particularly beneficial for Newtonian telescopes and discusses the need for modifications to the C11's housing to accommodate a fan.
  • A different participant expresses concern about modifying the sealed SCT and proposes using thermoelectric coolers as an alternative method for cooling.
  • One suggestion involves creating a styrofoam cooler for the optical tube assembly (OTA) and using dry ice to achieve a desired temperature before observing.
  • Several participants agree that pre-cooling the telescope to match expected night temperatures is more effective than trying to cool it actively during observations.
  • One participant mentions the practice of turning off cooling systems shortly before imaging to allow temperature equalization.
  • Another participant shares their experience of keeping their telescope outside in an unheated space to avoid the need for modifications.
  • Discussion includes methods for cooling larger Newtonian telescopes, emphasizing the importance of keeping the optics out of sunlight and allowing them to cool as night approaches.
  • A suggestion is made regarding the use of a Lymax Cat Cooler, which has received positive feedback.
  • One participant outlines a plan to install a heatsink and fan inside the telescope, with the intention of monitoring temperatures and potentially adding a peltier cooler later.

Areas of Agreement / Disagreement

Participants generally agree on the benefits of pre-cooling telescopes and the challenges associated with modifying a sealed SCT. However, there are multiple competing views on the best methods for cooling and the necessity of such modifications, leaving the discussion unresolved.

Contextual Notes

Participants express uncertainty about the effectiveness of continuous cooling and the importance of various cooling methods, indicating that further testing is needed to determine the significance of these approaches.

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Anyone have any experience with cooling a telescope mirror for image quality improvement? I have my C11 disassembled for some other upgrades and before putting it back together am considering adding a cooling fan. Anyone have opinions on how big of a difference it can make?
 
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Only in a Newtonian, Russ. Cooling helps speed up steady imaging.

A C11 is petty much sealed up, so if you wanted to add a fan, you'd probably have to make at least two holes in your rear housing. One for fan/intake, and the other for exhaust, and both of the holes should have cleanable/replaceable filters to keep dust and pollen off your optics. You can probably Google for advice on how to accomplish this.
 
Yeah, I'm wary of putting holes in my well-sealed SCT. Right now the mirror is perfectly clean. I found an intriguing alternative, using thermoelectric cooleres on the outside and fans to move air around the inside. I'll have to put some thought into whether I want to do this: http://scp3.org/main/index.php?option=com_content&view=article&id=79:installing-peltier-cooling-in-a-c14&catid=76:activecool-cooling&Itemid=71
 
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How about making a styrofoam cooler for the OTA and using your engineering skills to bathe the OTA in cool air using dry ice or whatever you can transport to a dark-sky site? If you can get the OTA to 40 deg in preparation for a predicted 40 deg night, that would be a help.
 
You are probably going to do better pre-cooling it to predicted night temperature (or keeping it cool from the night before) rather than trying to actively cool it while observing especialy if you live somewhere with big day/night swings.
 
mgb_phys said:
You are probably going to do better pre-cooling it to predicted night temperature (or keeping it cool from the night before) rather than trying to actively cool it while observing especialy if you live somewhere with big day/night swings.
Uh! Didn't I just say that?
 
Yep - didn't read the last sentence. ;-)
 
Well, yeah, what people are doing with the setup I described is just pre-cooling the scope and then turning off the cooler a few minutes before they start imaging so the temperatures can equalize. I suppose if I'm leaving the scope outside for a few hours before using it, I'll get a similar effect.

For Newts, people are leaving the fans on while imaging, but that wouldn't work with a peltier because there would be cold spots.
 
I leave mine outside most of the time [unheated enclosed porch. I would not put any holes in the tube. The closed tube prevents all sorts of evils from reaching the optics.
 
  • #10
People with larger Newts can cool optics using some obvious methods. Try to keep the scope out of sunlight to keep the outer parts cool. Try to point the optics pointed at the open sky in order to let the optics cool as night falls. The larger the 'scope, the more likely that you'll have to get inventive to cool it.
 
  • #11
How about a Lymax Cat Cooler, Russ? I've heard good things.
 
  • #12
It's a possibility, but I'm still hoping for the possibility of continuous cooling. I'm not sure how important it is, but I'd rather be set up for it and not need it than have to decide to go back and install it later (taking apart my OTA is something I never want to do again). And I really want to do some testing to find out how big of an issue this is.

So here's what I'm thinking I'll do:
1. Install a heatsink/fan on the inside of the base, with the fan pointing toward the back of the mirror.
2. Install thermocouples on both the heatsink and the back of the mirror to monitor the temperature.
3. Drill and tap a couple of holes to mount an external heatsink and peltier in the future if I want it. If I don't use it, I can just use screws to plug the holes.
 

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