If you, like me, live in a part of the World that experiences cool even cold nights then you will know that one of the biggest challenges facing the amateur astronomer is keeping warm. Unfortunately the best views are achieved during some of the coldest nights and when the telescope and observer are out in the elements. The telescope should be setup a few hours before nightfall to allow it to acclimatise to the conditions but what of you, the astronomer. I have spent many years attempting to keep warm and its the approach that seems to work for me that I will share with you now.
One of the easy traps to fall into when dressing for a nights observing is the idea of layering, loads of thin layers and you will be toasty warm all night. WRONG, at least in my experience. This approach relies on a certain amount of moving around and physical exertion for the body to generate enough heat which is then trapped amongst the layers you are wearing. Astronomy has to be one of the least active pastimes I have ever come across and certainly doesn’t offer many opportunities to generate internal heat. When observing I find a little layering with a whole load of insulation is the only certain way of keeping warm.
I start with a layer of thermals which are made of synthetic materials and incorporate a matrix of reflective dots on the inside to reflect any escaping body heat back in. This layer is a long sleeved top and long legged trousers. The top is tucked in to the trousers and some thermal socks pulled over the trouser legs helps to trap as much heat in as possible and stop cold air getting in.
On top of this is a mid-weight long sleeved shirt, still tight fitting and made of polyester or some other synthetic material. This is tucked in to a pair of fleece lined and wind proof trousers for insulation on my legs.
Top Insulation Layer
On top of all this is a long sleeved fleece top also tucked into the fleece trousers followed by a pair of thick woolen socks. On top of all this is a heavy duty down parker style jacket.
Head, Feet and Hands
The advice of looking after your extremities is absolutely true and especially for astronomy. Standing around in a cold field doing little or no exercise means you must conserve as much heat as possible.
Its true that most heat loss is through the head and I find a fleece lined knitted hat works best although its important to ensure your neck and ears are covered too. I do this either with a fleece neck gaiter (a tube of material that sits around the neck) or with the high collar of my jacket but I find the gaiter to be most effective. If its windy I will pull the hood of my jacket over the hat to help provide a little more wind proofing.
There is also a surprising amount of heat loss from your feet and its the transfer of this heat through to the cold ground which is the problem so good, insulated boots are a must. Its important that the boots you get aren’t too tight so take along the socks you will be wearing and ensure you have room to move your toes. Don’t forget, this is about standing still in a cold environment. You want to be able to move your toes to encourage blood flow to your feet and keep them warm. You should choose a boot that is well insulated in the sole as well as the main body of the boot. I must confess, I cheat and use heated boots. They are great, as battery powered (rechargeable) heating elements in the sole stop the heat transfer and keep my feet toasty warm.
The final area to consider are your hands which I find the toughest part of my body to keep warm. With eyepieces, tiny screws and allen keys, I find I need to maintain my dexterity but need insulation to keep my hands warm, particularly as most parts of the telescope and mount are made of metal.
There are ways to deal with this, and here is my imperfect but functional system. I start with a thin pair of thermal gloves. I then wear a pair of medium weight fleece gloves which provide most insulation but if the temperature drops below about -10 I place an electric or chemical hand warmer in the palm of my hand in each fleece glove.
I have learned a rather neat trick from some friends of mine who have worked in extremely cold conditions which is to swing my arms back and forth for a good few minutes which forces blood into the hands through centrifugal force. Its best to keep your hands lower than your heart as this minimises stresses on it. Surprisingly, it works and lasts for quite a while.