Cooling fans on newts

[mik]

Hello i was thinking of putting a diy cooling fan onto my XLT150 but am wondering if it is worth the effort, my mind tells me that the reason for cooling fans is to help the cooldown on large thick mirrors and the cooldown on a 6" is pretty quick what do you think is it worth it.

Mick.

[Doc]

I have a large fan on my 16" but believe me it needs it.

A 6" leave it outside for about 1 hour before you start observing it should be cool enough.

[mik]

Thats what i thought Doc thanks

Mick

[supernova]

I have a cooling fan on my 16in dob and it takes the thermal curents out of the ota.

But if your are taking pics shut it off because it can cause vibration in the image.

Bernie.

[nitram100]

I mounted 3 cooling fans underneath my mirror, just behind the mirror cell because it was taking about 2 hours to cooldown. Now it cools down in about 20 minutes.

[MikeP]

What's a sensible cool down time for my 12" FlexTube? It is stored in an uninsulated shed, so it must be pretty close to the ambient temperature when I take it out.

Mike

[TheThing]

Both my 6" Newts are stored in an unheated shed and I find that half an hour is plenty enough for them to cool down. Probably less than that, but half hour give me time to become 'dark' adapted. Surprisingly, even the unheated shed can be a couple of degrees warmer than the o/s if it's been a warm day!

[Whippy]

What's a sensible cool down time for my 12" FlexTube? It is stored in an uninsulated shed, so it must be pretty close to the ambient temperature when I take it out.

Mike

An hour tops Mike? I guess your storage must be a bit like mine (without the leaks I presume) and my 6" Mak-Cass only takes about an hour and they can take ages if kept indoors.

Tony..

[vlebo]

I agree with Tony , Mike, my two scopes take a maximum of 45 mins to cool down, mind you my garage in the winter is like a butchers cold room, ice cold beers to hand all year round.

[themos]

Right! I improved the mounting of the fan on my 12" Skywatcher 300P last night. I should add a baffle, too, to avoid recirculating air. I'll have to mount a webcam and take movies of Polaris every 10 minutes or so, both with the fan on and off. That should tell us something about how long it takes to settle down thermally. The fan I use has dimensions 80x80x15mm and I reckon it should be good for about 20 cubic feet per minute.

[themos]

This :

http://www.fpi-protostar.com/bgreer/fanselect.htm

suggests that it should take at least 30 minutes (for a 10" mirror) if you have sufficient airflow.

[mik]

Thanks for all the reply's

I look forward to your results Themos should be interesting.

Mick

[themos]

Very misty tonight, shame.

[mik]

Same here grrr.

[rusirius]

How do you know when its cooled down sufficiently?

[cloudyskies]

i fitted a fan and speed control to my 200mm skywatcher newt and the cool down period can be as little as 15 mins some nights.

although i havent found it helps to leave the fan on whilst using the scope.

[themos]

How do you know when its cooled down sufficiently?

Experienced observers can tell the difference between the effect of thermal tube currents and the effect of atmospheric aberrations ("seeing"). I can't, not yet.