Minimum temps for gazing

[Andy R]

Hello all,

with forecasted lows of -2/3 c expected over the next few days for where I’m located, which usually means clear sky’s (touch wood) is there a minimum temperature not to exceed for using your telescope.

sorry if it’s a silly question but I don’t mind the cold but my telescope might not perform well on frosty nights. 

 

Thanks

[paul mc c]

There shouldnt be any reason why,the only problem is if your scope runs of batterys the cold can mess them about,what set up do you have.

[AstroFin]

Hi Andy!

Here in northern Europe most observing throughout the year is done in sub-zero temperatures. I regularly use my Celestron CPC in temperatures ranging from -5 to -15 degrees Celsius. The lowest ever temperature I’ve observed in was -30 Celsius with my local astronomy club’s Celestron C11. ?

If your telescope is covered in frost, remember to keep the lens caps off after bringing the scope inside to allow the water to evaporate. If your mount has a hand controller, the display wil most likely slow down significantly. The stock grease in most mounts is not very good in lower temperatures, but for occasional observing below freezing the grease will do ok.

I don’t think there is minimum temperature for using a telescope. Usually it is the observer, not the instrument that fails! ?

Tomi

[Andy R]

Jolly good thanks for tips and pointers for the batteries and lens. 

-30 you say now that’s cold.  

[Ruud]

Just dress warm, don't lick the tripod, and when you can no longer feel your nose or your toes it's time to go back in.

[jetstream]

I observe in temps down to -40c and there are a few things to keep in mind. I would not ever take an oiled spaced refractor out in these temps, air spaced is fine but the lens cell might distort the glass. Dobs are very tough in the cold weather and are my preferred choice- no issues here. My AZ EQ6 does not like very cold temps- the cables and controller face challenges but the mount does work.

One of the most important things when observing in the cold happens when you take your scope (and eyepieces) back inside- you must bring it in insulated with something to keep severe frosting at bay.

btw, last night in -28c temps I was observing the moon in the 15" dob, it worked perfectly and the views with the binoviewers were beyond stunning...

[paul mc c]

10 minutes ago, Ruud said:

Just dress warm, don't lick the tripod, and when you can no longer feel your nose or your toes it's time to go back in.

What are you....a man or a mouse....lol,some of my happiest times was licking tripods.

[dannybgoode]

Well I’ve just been out and it’s chuffing cold. I think you’d break before your gear but as above - batteries don’t do well in the cold. 

I use a mains power supply so nothing really to fail except me!

[Carbon Brush]

Yes stay warm. Several layers of clothes everywhere.

As mentioned above. Batteries are the first item of equipment to suffer the cold.

This is one reason (there are others) that big lead acid leisure batteries have been used for astro work.
You might use 2Ah to 10Ah of battery in night running a mount and some dew heating.
If you 100Ah battery that is peforming really badly in the cold, so what? You are not asking for more than a tiny fration of the capacity.
Also if you have the battery nice and warm in the house before starting, it takes a long time to cool being large.

A small NiCd or NiMH pack is completely different. You expect to use a significant proportion of the capacity in a night, so loss of performance in the cold does matter.
Being physically small, it cools quickly.

There are good arguments for keeping any batteries for astro kit in the warm house for charge, then in an insulated box for use.
Remove from the insulated box for charging of course.

Hope this helps, David.

 

[Andy R]

On 17/01/2019 at 18:15, paul mc c said:

There shouldnt be any reason why,the only problem is if your scope runs of batterys the cold can mess them about,what set up do you have.

It’s a nexstar I’m running it on a power pack with a batteries as back up. I had a bit of a cold the past week so tonight I ventured out in 6 inches of snow and well lesson number one wear suitable shoes with a bit of grip, took a tumble and nearly wiped out my setup without even looking at anything. Lesson 2 make sure you know what yr looking at. I used solar align as a quick Waylon align.  I thought I was aligning with Mars it must of been Uranus instead, Mars must been behind a hill. I took the sky tour and didn’t see anything really, I selected Orion Nebula and I was looking prob 10 degrees too low d’oh. Lesson 3 buy a dew shield(I have one on order) I’m looking at andromeda(first time I’ve found it) I’m thinking it’s a bit dim, got my binoculars out and wow my first galaxy in clear view amazing. My corrector plate was covered in dew which was starting to freeze. Anyway it was a great hour or so observing, shame I can’t feel my toes. Can’t wsit to see Mars really but it’s too low and I have a 1800ft hill to the south and west of me. 

Andy r

On 17/01/2019 at 18:25, AstroFin said:

If your telescope is covered in frost, remember to keep the lens caps off after bringing the scope inside to allow the water to evaporate. If

Sound advice thank you sir

[SIDO]

Was out this morning for some planets and the moon with my st80, temp was -31c windchill at -45.5c. 

Two 30mm eye pieces, one in the scope one in my pocket in case I accidentally outgased on the one in the scope, about 40 minutes was all I could take with the best winter clothing in layers...Intended to take a couple photos but the camera app kept malfunctioning in the low temps. I use a piece of blue foamboard insulation under my feet and electric handwarmers in my gloves. 

This may have been my coldest session to date as they say we are breaking records today,  likely though others have been out in worse.

            Dress warm, if you start to feel cold get inside ?

                          Freddie...