What are your opinions on fans in an observatory ??

Hi All,
Given the scorching heat today, I went out to maplin today and got 4fans + controller (going cheap) for the observatory (soon to be). I was pondering on what would be the best locations for them.
Would you have 2 low on one wall blowing air in and 2 high on the opposite wall blowing air our, or would you have one on each wall..

This might seem trivial, but once the holes are cut for this, there is no going back, so I want ot get it right first time.

Those of you out there who have observatories, what have you done?

Dave - not having an observatory, I can't advise you on what I've done. But I've been involved in industrial ventilation projects in the past.

I'd recommend two low, two high and on oppposite walls - just as you say. You probably want to draw air in at the bottom and expel it at the top. You'll get a laminer-type flow in the space - I assume you'll be filtering the air? If not, you might get dust build-up on objects in the path of the flow.

0.2 cents worth....

Cheers

Dave McD

Dave seems right Dave... :lol:

I would think air-intake at the bottom, and extraction near the top/higher up - cool air is the best, warm air causes problems as you know. Considering almost all of your observing would be at night, the cooler the better prior to starting observing.

Seanie.

Hi Dave,

I had considered the fan option for the big RORO observatory here. Indeed it shoud work.

However, I finally decided on 2 inch polystyrene insulation on ceiling and walls, held up by mesh and studs. The metal enclosure was incredibly hot out side yesterday. So there is no heat transmittence to the inside. It works, but still the hottest day I had to open the front door to get some air circulation. Its always been a concern for me the stability of the mirror. At least there are no extreme swings of temperature, this would be a problem when it comes down to keeping the same figure of accuracy of the main mirror.

I am in the middle of constructing a giant wind barrier for the big telescope. I find that there are clear nights with wind, and I have difficulty in imaging.

Eamonn A

Thanks for the feedback lads,
I'll go with 2 up 2 down, interesting Eamonn that you say the metal enclosue gets very hot, does it get warm to the touch on any sunny day?

Dave,

I only discovered your post today with my apologies on a belated response.

The metal enclosure does gets hot on the outside surface on clear sunny days in mid summer. This is not a problem for the majority of the year. Hence the 2 inch thick insulation to reduce heat transmission to the interior.
I think your idea of fans 2 up 2 down will definitely reduce the heat.

BTW I have completed the giant wind barrier. This can be moved to different positions depending on the direction of the wind. Its 33 feet X 16 feet.

Eamonn A