Running usually, at night time on a cliff near my home has put me into consideration regarding clothing for night observations in winter time. Temperature drops each day so we have to take some precautions. Well ,while you run you’re pretty warm already, so cold is not a serious problem but sweat can be a bugger. To solve this, most runners use isothermal light clothing. Weights little and passes sweat in the outer layer so that skin remains dry and warm.
So what can we do if we stand still in the night on a hill/mountain at winter time with -3 or so celcius ? Most books suggest dressing like a bear or taking a portable alogon/gas heater and a portable electrical generator with you or even use chemicals on your skin to stay warm.. My opinion is that its highly impractical and a complete energy waster. This is why past generations have devastated nature..
When Im off to star watching for a whole night I usually dress lightly and with some tea in a thermos, I manage to stay warm and not end up with pneumonia in the morning. Lets imagine that human body is a 4 part machine. Feet, lower body part, upper body part and head. All must be protected from cold with feet being the most durable and head the most vunerable.
Feet: Mountain climber’s socks or even better hunter’s socks. Hunters socks are the best way protecting your feet from cold weather. The cost is ridiculous (about 3-10 Euros from Praktiker) and keeps the feet warm even in extreme weather. Remember that these socks are designed to keep warm (usually stationary) hunters. As for shoes climbing boots are light and sturdy but I find stability oriented athletic shoes more practical when there’s no snow.
Lower part: Jeans with lots of pockets, or woolen trousers and isothermal underwear are just fine. Isothermal underwear may cause itching but its natural i guess, except only if you’re allergic..a great percentage of its material is sheep wool.
Upper part: Isothermal light sweater and isothermal woolen gloves (or find a cheap pair and cut the finger covers to be able to hold your eyepieces/focuser), woolen sweater (sheep wool is the best – a constant reminder…), and a runner’s wind stopper jacket with inner woolen layer will do.
Head: Wool cap and scarf or buff in balaclava setup will do. Both in extreme conditions. Covering your mouth must be one of your first priorities since cold air will harm your lungs.
So the magic words are layers and wool. Most shepherds (at least in my country live on mountains) could bare cold because every piece of cloth on them was made from their primary resource, sheep wool.
The most technical in the above list is the thermal underwear, which can be found in various prices and qualities in extreme sports stores. Mine are able to withhold body heat at -9 Celcius tops and cost around 40 euros each (sweater and pants). There are others that are designed for -20 and -30 Celcius but are a bit expensive, starting at 70 euros each.
The whole idea is to be as light as possible or even better wear as less as possible, but manage to keep your body temperature stable. I believe that being lightweight, fit as possible and keep breathing from the nose, will help overcome sleep, cold and fatigue.
You might also consider doing some workout while you’re standing. Keeping the blood in constant flow will keep you warm enough. Walking around, a bit of stretching, moving arms in circular movements or even better some simple tai chi forms will help.
Also a Hobo stove is a very nice (ecological and fire safe) option if there’s not a house to stay. You can make one using an old small metal barrel or buy a commercial which might be more portable. Also the usage of the hobo stove does not greatly affect your night vision.
If you feel weird at any time or for whatever reason, stop. Killing oneself or losing your health is an unnecessary extremity for a hobby. If you want extremities start smashing light bulbs with police cars in view ;p