With winter nearly upon us, the days are getting shorter. For amateur astronomers this means that you won’t have to stay up until after midnight to get dark skies for observing. On the downside, it also means that it’s going to be a lot colder out at night. An important factor to consider, when dressing up for astronomy, is that you won’t be moving around a lot when you’re stargazing. It’s dark and you’ll be looking up a lot. Because you’ll be observing on nights with clear skies, it will also be much colder than if it was cloudy.
Whether you’re a night photographer, amateur astronomer, or both, often the difference between an enjoyable and miserable experience will be how comfortable you are in your environment. Something to cover your head is a good start. While it’s a myth that most of your body heat in the cold is lost through your head, any uncovered area of your body results in faster heat loss and your head is often uncovered. You should be careful when considering a hat though, because you could easily find your hat brim pecking at your carefully targeted telescope when you lean in for a look through your eyepiece. A toque is a better choice. A balaclava might seem the ideal head-wear, right up until your neighbours start putting 911 on speed dial every time you go out into the backyard. Similarly, operating in the dark of a city park, wearing a ski mask, could result in unwanted consequences with the police. So unless you’re at a star party or very remote location, leave the balaclava at home.
Wear thermal long underwear when you’re observing at night. I’d recommend even wearing them observing in the summer. It’s an easy thing to throw on an extra upper body layer, but once you’ve left home, it’s too late to change into your long johns. You’ll want to stay away from useless cotton long underwear and stick to wool or high tech materials, like polypropylene. The best thermal long underwear I’ve ever owned were military issue and you can buy new ones at most military surplus stores. They’re about ten times better than the best civilian grade long johns for about one third of the cost. I had a lot of time to compare the merits of different types of thermal wear when I worked in a warehouse freezer, while operating heavy equipment for hours at a time.
Even during the summer, when I’m out at night, I keep a pair of light gloves on hand, because uncovered skin gets cold fast. I use what are sometimes called “minute” gloves, probably because when performing hard labour they’ll only be good for a few minutes. They often have tiny rubber beads on either one or both sides, for better grip, and are very inexpensive cloth gloves that you can find in any hardware store. You won’t want heavy gloves when you’re observing because you will lose too much sense of touch to use your equipment when you’re wearing them. Wools socks and scarfs are also a good idea.
Make sure you don’t wear any clothes that are too constricting, because cutting off your circulation isn’t going to help you stay warm. That goes for your footwear too. Dress in layers and stay away from cotton. High tech fibers and wool are better. You’ll want a hard shell jacket as your outside layer, to keep the wind from robbing you of your warmth. I tend to get most of the clothes I use for astronomy from outdoor adventure or military surplus stores. Keep at least one more layer of clothing on hand than you think you’re going to use, but don’t leave unworn clothes exposed to the elements or they might be soaked with dew by the time you need them. Keep clothes in a sealed bag until needed.
Eating and drinking are also important factors to determine if you’ll stay warm outside at night. You’ll want to eat a good meal before you go out, but try not to eat a big meal minutes before leaving or at least in the short term you’ll be even colder than if you hadn’t eaten, as your body diverts energy from keeping you warm to digesting your food. Hydration is a tricky issue for amateur astronomers. While you’re bundled up against the winter night, there might not be washrooms available or you might not be in a place where you feel comfortable abandoning your expensive equipment. You want to drink enough that you’re not dehydrated, but not so much that you’re running to the bathroom all night instead of observing. In cold weather, our sense of thirst is dulled, so just because you’re not thirsty doesn’t mean you’re not dehydrated. Also, make sure to go to the bathroom before you leave, because your body will divert energy to keeping human waste products warm that could be better used keeping the rest of you warm.
Some amateur astronomers use chemical hot packets for heating and while they’re nice for short term use, they create a lot of garbage and the money you spend on them over the long haul can be better put to use buying a new eyepiece. I like pocket charcoal hand warmers. They consist of a felt covered metal case that you burn inexpensive sticks of charcoal inside of. You can either put the case in your chest pocket, to warm your body core, or use it to warm your hands. I’ve used these charcoal burners for wilderness winter camping and they can really take the edge off the cold weather. There are amateur astronomers who choose to escape the cold by operating their telescopes remotely with a laptop, from within the confines of their own home, but for the rest of us it’s time to bundle up against the cold.