Lowest acceptable temperature for observing

[Obi Wan Ken00bi]

Quick question:

What is the lowest temperature before equipment starts freezing up beyond the point that you can't use it anymore? Tonight it will be around minus 5 degrees, can I still go out or will it be hopeless?

Thanks a lot in advance!

[jarralad]

hi obi.

not a problem,been out in -10 at kielder,sgl members from usa and canada,finland sweden,even colder,just make sure your wrapped up.

[nicks90]

i was out last night for an hour in minus 6C. the scope and equipment was absolutely fine, however I wasnt!!! As it was a spur of the moment session, i wasnt wrapped up very warm and my hands and feet were numb after 45 mins.

and i made the misake of breathing out near to an ep in the focusser and it instantly fogged up and wouldnt clear... so that meant for the rest of the session i couldnt use the meade 6mm

[JamesF]

There are SGL members who live in forn parts. And cold forn parts at that. I'm sure at least one who lives in Canada has been known to go out observing when the air temperature is below -20C.

James

[E621Keith]

I wouldn't worry about it. The temperature in UK or Nethelands won't draop cold enough to affect the scope's performance. Telescopes are designed to work in cold cloudless nights.

While there are reports of telescope stop working in cold nights, those reports generally come from area such as Canada and Alaska, where the night time temperature can drop belpw -20deg C. -5deg won't affect your telescope at all.

[redneon]

It's interesting that you mention fogging up the focuser. I think I might have done that last night to my finderscope. After an hour or so I noticed that I could no longer make out the crosshair in my finderscope so I assumed it was dew or fog. There was a lot of freezing fog in the air. I didn't know if it was ok for me to wipe it clear though, so I just left it and persevered

[Obi Wan Ken00bi]

Thanks a lot for the fast answers! I'll make sure to take more care for my own warmth then the telescope's/

i was out last night for an hour in minus 6C. the scope and equipment was absolutely fine, however I wasnt!!! As it was a spur of the moment session, i wasnt wrapped up very warm and my hands and feet were numb after 45 mins.

and i made the misake of breathing out near to an ep in the focusser and it instantly fogged up and wouldnt clear... so that meant for the rest of the session i couldnt use the meade 6mm

That a good pointer, don't exhale into eyepieces, finders, camera, etc.

[JamesF]

I wouldn't worry about it. The temperature in UK or Nethelands won't draop cold enough to affect the scope's performance. Telescopes are designed to work in cold cloudless nights.

While there are reports of telescope stop working in cold nights, those reports generally come from area such as Canada and Alaska, where the night time temperature can drop belpw -20deg C. -5deg won't affect your telescope at all.

Absolutely agree. Your willpower is likely to fail before the scope will. Batteries don't take extreme cold well though, and if you've been out at -10C then I'd try to avoid bringing the scope straight back into a room at, say, +20C if possible. The resulting thermal stress probably wouldn't be a major issue, but there's no point causing it unnecessarily.

James

[JamesF]

That a good pointer, don't exhale into eyepieces, finders, camera, etc.

If you're not using an eyepiece at the time, keeping it in a pocket is helpful when it's cold.

James

[Obi Wan Ken00bi]

Last time I went out, it started to freeze a little at the end and some of the equipment had some frost on it. Should I clean all the equipment (eyepieces, barlows, etc) afterwards or just leave it be?

[Planetesimal]

I'd bring your equipment indoors and let it dry naturally (with the lens caps etc. left off). It'll be fine in the morning and you can pack up then.

[JamesF]

I'd bring your equipment indoors and let it dry naturally (with the lens caps etc. left off). It'll be fine in the morning and you can pack up then.

Exactly that. Just arrange things so any drips will run away from the optics.

James

[VigdisVZ]

Image was taken -20, no problems Dew shields become frost shields, and you need good clothing.

[Obi Wan Ken00bi]

Image was taken -20, no problems Dew shields become frost shields, and you need good clothing.

Haha nice, I'll think of this setup when I'm cold tonight knowing some people have it far colder than me

[VigdisVZ]

Haha nice, I'll think of this setup when I'm cold tonight knowing some people have it far colder than me

Actually Chris is has his scope and mount outside for days at a time with just a tarp over. So it should be ok.

[Double Kick Drum]

After a few hours out in the cold, it's my brain that goes first.

I tend to keep replacing the scope caps when not in use (while I am looking at maps or fiddling with eyepieces). It keeps dew or frost at bay for a little longer.

Clear skies!

[Moonshane]

I agree, the scope can handle pretty much anything we'll experience coldwise. On the other hand it does get very cold for human noses beyond about -10c. I had lots of frost on my scope last night at -5c.

[Marki]

2 of my 'fracs were made in Siberia....I'll give in way before they do

I always use the dew shield on my SCT, and keep eps in my pockets when not in the tube. I just bought some new boots with the express aim of trying to keep my feet warm as thats the part of me that really suffers when it starts to get below zero.

[nicks90]

After an hour or so I noticed that I could no longer make out the crosshair in my finderscope so I assumed it was dew or fog. There was a lot of freezing fog in the air. I didn't know if it was ok for me to wipe it clear though, so I just left it and persevered

hmmm, i get that on my finderscope too - i think it might be worthwhile puttng a little cap on the end of it once i;ve zero'd in on a target!

[starman1969]

I left my scope out for several hours last night. It had frost all over it but it still worked normally. I had to blast the front element with a hairdryer when it started to fog up.

A power tank is essential, too.

[VigdisVZ]

Battery tanks dont like cold. If you have a transformator for powering the mount from the grid, or use an insulated box if you plan on using the power tank outside for more than a couple of hours.

Also you have to take care to put caps on binos, EP's and finderscopes, aswell as having proper dew shields and maybe heaters depending on scope typ. One way is to put the caps on the EP's and have them in your inner pockets when they're not in the focuser.

[Planetesimal]

I've found there's nothing you can do to keep a newt's secondary free of dew other than a hairdryer.

[Obi Wan Ken00bi]

Summarizing:

- Keep dustcaps on equipment as much as possible

- Don't breath out on equipment

- Bring a hairdryer

- Bring warm clothing (also thick socks!) and hot chocolate

- Afterwards, let it warm up slowly

Thanks a lot, I will let you know if it was worth it.....

[VigdisVZ]

Dont stuff your boots with too many socks. You need blood circulation as well. Standing still is also a feet killer. Walk around much. If you can stand on something insulating, like pine branches or maybe a surplus camping mat, do that, it cuts cold radiating up from the groun into your soles.

[Mr Spock]

I've been out in -7°. The scope was fine but I regretted it the rest of the night...