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Air Conditioning System in Large Observatory

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#1 Howard Gao

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Posted 27 August 2021 - 10:56 AM

Hi All

 

May I have some advices on whether AC system should be used in large observatories in summer where the temprature and humidity is high? Will it have impact to performance of the telescope (e.g. one meter CDK or Cassegrain)?

 

Thanks

Howard



#2 Astrojensen

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Posted 27 August 2021 - 11:05 AM

It could have a HUGE impact, depending on how much the temperature drops by nightfall. If there's a rapid drop, then having a temperature controlled observatory could vastly improve the seeing inside the dome and the telescope. 

 

All large, professional observatories use it. 

 

 

Clear skies!

Thomas, Denmark



#3 rgsalinger

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Posted 27 August 2021 - 11:17 AM

Absolutelly. We use a portable air conditioner on our RC 25" to cool the mirror about an hour before sunset. (There are holes in the backplane of the scope that we can use.) If we don't do that, then on hot or cold nights and temperatures shift, it can take 4 hours for the mirror to fully acclimate. 

Rgrds-Ross


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#4 MJB87

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Posted 27 August 2021 - 11:58 AM

This may seem trivial, but I found it useful to have an air conditioner that I can connect to my LAN and control remotely. In the summer I'll set the temperature (remotely) to match I I expect when I hope the dome/ROR. It is nice being able to do this without being at the observatory.



#5 mark77

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Posted 27 August 2021 - 12:07 PM

This may seem trivial, but I found it useful to have an air conditioner that I can connect to my LAN and control remotely. In the summer I'll set the temperature (remotely) to match I I expect when I hope the dome/ROR. It is nice being able to do this without being at the observatory.

What AC are you using that can be controlled remotely, sounds like a very good idea.



#6 MJB87

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Posted 27 August 2021 - 03:37 PM

I'm using a Friedrich Chill Premier unit, but mine is probably smaller than what you are thinking of.



#7 drprovi57

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Posted 27 August 2021 - 03:53 PM

I installed the MrCool DIY mini-split 12K HVAC system into my observatory - can also be controlled via the local LAN on an iPhone or on Android app.  Having a split system places the compressor/heat-exchanger on the outside - hence the inside head unit is whisper quiet.  I can control the inside temperature for both hot summers and cold winters (nice to have some heat inside dome while I am working on equipment).  I put the system into fan mode while imaging/observing.  The system also provides dehumidifier capabilities to ensure humidity remains under 50%.  The MrCool DIY system is easy to install (lots of YouTube videos) - took me 4 hours total.  The system is considerably more expensive than a standard wall/window AC unit - but given the expensive equipment and comfort level it was worth the hight $$ cost to me.

 

Jason


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#8 Howard Gao

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Posted 27 August 2021 - 07:35 PM

Thanks for the advices guys. So what after you open the observatory for observing? Do you still keep the AC system running? In my place if we don’t do that the temperature and humidity is too high. But if we do it my concern is it will have impact to telescope performance as there will be some turbulence within the observatory. I asked a few friends in big observatories and it seems they all shut the AC system down during observing.

#9 MJB87

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Posted 27 August 2021 - 08:36 PM

Once I reach outdoor temperature I turn off the system. However, I usually don't image much in mid summer. Just too hot and too many bugs.



#10 meganders

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Posted 15 September 2021 - 02:46 AM

My friend works at the observatory. They use about five portable air conditioners to cool everything down in time, according to the schedule.



#11 Howard Gao

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Posted 15 September 2021 - 07:29 AM

Thanks for sharing.



#12 Oberon

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Posted 15 September 2021 - 09:49 AM

Thanks for the advices guys. So what after you open the observatory for observing? Do you still keep the AC system running? In my place if we don’t do that the temperature and humidity is too high. But if we do it my concern is it will have impact to telescope performance as there will be some turbulence within the observatory. I asked a few friends in big observatories and it seems they all shut the AC system down during observing.

Most would, but not all. The AAT air conditioning system was designed to operate with the dome open without any deleterious effects, but this is probably unusual. If you can use an air conditioner to maintain a pool of cooler air below the telescope without impacting on the incoming beam, then yes it is worthwhile as it will reduce risk of warm plumes rising into the beam. But it has to be designed and engineered to achieve that, otherwise you risk mixing warm and cooled air within the dome and in the beam, which will destroy the seeing.


Edited by Oberon, 15 September 2021 - 09:50 AM.



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