Can nights be too cold for a telescope?

[zork]

So... I have been checking out the sky for a while with my bins and the time is coming for getting a telescope. I am kind of leaning towards a bigger sized dob, but I am unsure if I should put that kind of money on a telescope since most my stargazing nights will be pretty cold.

Summers... Well... In summers the sun will start to go down around 10pm and it will rise about 4:30-5 am.

Winters will, of course, be dark. But cold. Around december-februari can it be as cold as -20-30 celcius where I live.

So my question is.... Can it be too cold outside for a telescope? It can be too cold for me, sure, but for a telescope?

[albedo0.39]

I hear stories of people in the USA working with scopes down at these temperatures, but if you have a dob of any reasonable size then there is not much to remember except that if you keep it inside and then move out, you will have a gi-huge mirror cool down time.

If however you have lot's of electronics and such like then it's often worth remembering that some microprocessors don't like temperatures below 0 degree C.

Batteries are also poorer performing in the cold

Apart from that, I know of no lower limit... but I'm happy to hear of what the more experienced folks think

[Doc]

You will need some sort of heaters set up to stop mirrors freezing over and finders as well.

Carol's the one to ask advice from, she often observes at these types of temperatures.

[Gonzo56]

Too cold for telescopes? Not! My friend and I are the hardier amateurs of our club. Cold weather doesn't deter us from observing with proper precautions: warm layered clothes and hot chocolate. We normally take a break every 90 minutes or so to warm up.

Our large telescope and the club telescopes are stored inside a dome so they're always ready to go. Up till last year, the coldest we've observed was 15ºF and the electronics/pc's still worked. Last year hit bottom one night at 0ºF. The pc ran ok for about 90 minutes then started having issues with the cold. The cold didn't bother the telescopes at all. I really don't want to go through that again.

By the way. I live in Mansfield, Ohio. It's about half way between Cleveland & Columbus. Last year was about the coldest winter we've had in quite some time. Not a lot of snow but it got cold around November 1st and stayed until about March 15.

John

[oceanheadted]

I read a post from a guy in Norway who was observing in -20-30C. I think he said the problem was the grease in the mount which needed to be changed for a special low temperature formulation because it was too stiff.

If it gets very cold metal can behave strangely and fracture more easily, but by then you would probably be suffering from frostbite!

[SteveL]

If you can keep the optics from freezing over (or the grease from freezing solid!), then you shouldnt have any issues. First image is when my battery packs gave up at -6C and the correctpr froze. Second two are from -8C (running from mains-to-12v at that point).

Biggest problem at this temperature is ensuring that any bare fingers dont freeze to any metal bits (And that USB and power leads dont fold easily to go back in the boxes afterwards!)

[Astro_Baby]

PLastic can also fracture at very low temperautures so care is to be exercised. Metal can shatter like glass especially pot metals. That means stuff like HEQ5s and EQ6s can, in theory anyway, exhibit metal failures. I have seen a few on CN where bits of mounts have just broken probably due to extreme cold.

I was out at the start of this year with the Nexstar 4 and its corrector and tube were just cased in ice after about 40 minutes. My power tank went flat at about the same time.

[calibos]

Did a public outreach at a national park for 200 hundred people here in Wicklow and it was minus 5. Didn't feel the cold because I was well layered. Only realised it was sub zero when packing up and I noticed the OTA of my dob was covered in a layer of frost. Didn't have heaters back then but my mirrors nor EP's dewed/frosted up thanks to reasonably low humidity.

[Talitha]

Hi Zork, the equipment is replaceable, just be careful about frostbite.. that's rule #1.

Mick's right, i often observe in pretty cold temperatures, but the worst thing that's ever happened was shattered film when it was -25C. My friends in Alaska warned me not to advance it too fast, but it was such a beautiful Auroral display.

Outside of frost on the mirrors and eyepieces, i don't think you'd have too much of a problem with anything as long as you don't drop an eyepiece or try to force anything that doesn't seem to want to move.

A mechanical tracking platform might give you problems, though. The tracking on my LX-10 used to start binding up at about -7C until i re-greased the worm gear with snowmobile grease. Seriously, that stuff they apply in the factory turns to glue when it starts to get cold.

Moving the scope from a warm house to a cold deck never caused any problems either. My scopes are kept in the living room where the woodstove keeps the temp between 21C and 25C, and sometimes the outside temp is about -12C. Even with such a drastic temperature change, there's never been a problem with the mirrors or lenses on any of my scopes.

Well yes, actually, there was.. condensation formed on them when i brought them back into the house after the session, and the water spots were a bit annoying. But i remembered what my Aurora friends said about the cameras.. put them into a plastic bag till they acclimate to the house temperature to avoid condensation.

So i got some large lawn/leaf bags and put the equipment into them before bringing things into the house and it solved the problem beautifully. Close the bags tightly while outside, and don't open them up in the house till morning. Atlases, eyepiece case, power cords, mounts, everything goes into the bags except the tripods. I've no idea where you'd get a bag large enough for a Dob, though. Hope this helped.

[zork]

heya all, thanks for the info... since i have never been peeking through a scope yet, just my bins, i dont know how much electronics a dob comes with. i am not aiming for a dob with goto though. well, it gives me some to think about... the worst of this winter will be over by time i get a dob anyway. i just want to be prepared.

[brianb]

If however you have lot's of electronics and such like then it's often worth remembering that some microprocessors don't like temperatures below 0 degree C.

Actually they work better the colder you get them. Stuff a commercial microprocessor in a tank of liquid nitrogen (-190C) and you can just about double the clock rate that it will run stably at.

The big problem that many computerized scopes have at low temperatures is that the handset uses a liquid crystal display ... which ceases to operate at low temperatures. Same problem with PCs. The actual electronics, plus the mechanics of drives etc., will be fine provided they're kept dry - if moisture gets in & freezes then mechanics can seize up. So get everything running as soon as it's taken outside & slew the mount around every few minutes to keep the drives exercised. The handset display can be kept alive by keeping it in a thermally insulated "glove" and/or glusing a heating pad to the back of it. Batteries also benefit from a heated jacket, even if you have to use some of the juice in the battery to provide the heat!

The main issue with using any equipment in cold temperatures is being careful when handling it - always use gloves when handling metal, otherwise heat conduction can give you frost bite in a few seconds, and you may even get stuck to the thing.