Thermal Issues in cold place

BC · #1 31-05-2005, 04:03 PM

Hi again,

You guys were so helpful, I'll ask another question if I may. I've been reading about the thermal equilibrium issues on other posts. I live 900m altitude outside of Canberra so it's pretty cold with often ~ 20 degrees difference between day and night temps. Some threads make it sound like I'm completely wasting my time with a Newtonian at all as it will never work. Is it really this bad, or is an 8" better than a 10"etc

Thanks again,
BC

ballaratdragons (Ken) · #2 31-05-2005, 04:09 PM

Hi BC.

Newts are fine in cold weather. Any scope will work in the cold!
The only drama with scopes is fogging up (which can be overcome).

The difference between the 8" and the 10" is that the 10" may take an extra 10 or 15 minutes to equalise in temp. If you fit a fan the cooldown time is down to about 5 min for either size.

atalas · #3 31-05-2005, 04:12 PM

Hi again BC , no Its not a waist of time!you will have no problems with the newtonians just put them out for an hour or so before use.
A 10"is better than an 8"! just learn to collimate well and you will have a ball.

Louie

ballaratdragons (Ken) · #4 31-05-2005, 04:16 PM

But a 12" is better than a 10"

atalas · #5 31-05-2005, 04:23 PM

Mmmmmm! a 12" ! BC food for thought, now you might not understand this madness at the moment,but you will you will It gets us all in the end.

Louie

ving (David) · #6 31-05-2005, 04:48 PM

but a 16" is better than a 12"

frogman (Anthony Lord) · #7 31-05-2005, 05:05 PM

that about HECTOR ?

20"

BC

atalas · #8 31-05-2005, 05:20 PM

Please no more no more ! I can't take It any more!
Mmmmmm! 20" sweeeet !

Louie

frogman (Anthony Lord) · #9 31-05-2005, 05:32 PM

HAHAHAH gee you sounding awfully gay there Louie (not that theres anything wrong with our gay friends)...

atalas · #10 31-05-2005, 05:39 PM

No sorry to disappiont you Anthony, but I like women dude!hehehe

hey the post was about thermal issures! not gays.

Louie

atalas · #11 31-05-2005, 05:41 PM

Oh yes BC,just remember the rule "the bigger the mirror the bigger the fan"

Louie

fringe_dweller · #12 31-05-2005, 06:03 PM

If you can keep your newt out in a locked uninsulated shed (under a sheet maybe? and out of direct sunlight) - and not be worried about it that is - then it will be stabilised already, generally speaking. Mine only takes so long to cool down coz i am a woz

and cant stand to think of my scopes getting pinched or being lonely, so they are kept inside (not that i use them as much as i used too) - my 8" dob has an 9" oversized tube with clearance - which helps a bit as the air can move thru pretty quick - that only takes 30 min to cool down - even less sometimes - whereas my ten takes about two hours from coming from inside. Putting it out early, as was said, is the go as well.
Dont forget to point a dob?/newt straight up for at a half an hour at first to really get it cooling - just said that on the very slight chance you werent already doing it that way. You know roughly when its settled by doing a rough airy disc and looking for tube currents on the edge of airy disc corressponding to the inside of tube.
Cheers
Fringey

iceman (Mike) · #13 01-06-2005, 07:22 AM

Louie and Anthony don't stray off topic please

I keep my scope under our pergola out the back, so it's always at roughly outside temperature. During the summer months though, it gets afternoon sun on it so it can take a little longer.

A big difference between day and night temperature can be a problem, but it's not a major one and not really something you should be too concerned about unless you plan on doing imaging any time soon.

Anthony Wesley, one of Australia's best planetary imagers (check the solar system forum) lives in Canberra, and he's got peltier cooling hooked up to his 10" f/6 newt to bring the mirror down to ambient temperature quicker.

BC · #14 01-06-2005, 11:00 AM

Thank you all for your thoughts. Dobs and aperture seem to be all the go around here, and yet.... The quandry continues.

Thanks,
BC

h0ughy (David) · #15 02-06-2005, 10:12 PM

BC

when you have finished with your Newt, you can get a real telescope, and get a 12" SCT

Honestly I think you can't go too wrong with the advice just given above.

Late_Cretaceous · #16 05-06-2005, 01:54 AM

I have not experienced any thermal issues with my scope (a 10" dobsonian), which I store in my basement. If it is particularly cold outside (which is usually the case), I just let it equalibriate longer. Up to 2 hours to go from +20 to -20 C. I have recently installed a fan, and that should shorten the cooling time considerably. I have even experienced temperature drops of a couple degrees during observing, and not noticed any image degredation.

p.s. It sounds like you live in a great location to do some good observing!