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TELESCOPE COLD WEATHER VIEWING TIPS
Cold weather can really affect your viewing sessions using a telescope. Not only can it affect your comfort and the clarity of the views you get through the telescope, but it also has the potential to cause problems with or possibly damage your equipment. Plastic parts can become brittle and prone to breakage, batteries can be affected, and you may experience problems with the way your mount operates.Here are a few tips I have learned from my experience with the cold Canadian winters.
DRESS FOR THE OCCASION
This may sound pretty obvious, but remember you aren't going out for a walk or to shovel the driveway. Basically you will just be standing there in the cold, and without the heat generated by physical activity you will feel it a lot more. Dress for the occasion, and make sure you have warm boots, a hat, gloves or mitts, and whatever else the temperature warrants. A thermos full of hot chocolate is good if you plan on being out for a while.
SCOPE COOL DOWN TIME
If your telescope is warmer than the temperature outside, images might not focus properly. The heat radiating off the optical tube, as well as the mirrors and lenses, will create ripples in the air that will be magnified when you look through the eyepiece and blur everything if the difference in temperature is too great. If you have ever looked at road asphalt on a hot summer day and seen the "heat waves" distorting the air above it you know what I mean. The greater the temperature difference, or the larger the telescope, the longer it takes for the temperature to equalize.
DON"T BREATHE ON THE EYEPIECE
It's not like I expect you to breathe on the eyepiece and fog it up so you can wipe it like you would to clean a pair of glasses. All it takes is an ill-timed exhale as you approach the eyepiece, and it will either fog or frost up.
WATCH THE WATTERY EYES
In extreme cold your eyes can water and all it takes is one drop for the eyepiece to either fog or frost it up, whether it drips and lands on the eyepiece, or your eyeball gets too close and a drop touches the glass and gets sucked right into it by capillaric action.
USE A TELESCOPE COVER
Imagine how cold a telescope gets when it has been sitting outside in the winter for a while in the cold, dry air. When you bring it back into your warm car or the house, it is exposed to warm, relatively moist air. Within minutes your optical tube and mount will be covered with water that has condensed due to their cool temperature.This water will not only create spots on your mirrors or lense, but has the potential to create rust in spots that you can't see or wipe off (inside the mount), or harm any electric motors or circuitry. Bring a large garbage or yard waste bag, or any waterproof bag that will cover your scope and mount outside with you. Before bringing the scope in out of the cold, wrap the bag over it and seal it by taping around the outside of the bag over the tripod. This will prevent the moist air from coming in contact with the important parts of your telescope, and stop water droplets from forming.
CHOOSE YOUR LOCATION CAREFULLY
Warm mirrors or lenses aren't the only things that will create unsteady air in colder weather that will ruin your image quality. Heat from pavement that hasn't cooled down, clothes dryer air outlet pipes, or just looking over the roof of a house can do the same thing. My apartment balcony is great for summer viewing, but the heat coming from the building makes for some pretty lousy observing in the colder winter months.
PINCHED OPTICS DURING EXTREME COLD
If it is too cold outside, you may have problems with pinched optics. This occurs when the mirrors or lenses in your telescope shrink so much from the cold that they don't align properly, and the image will not focus. This is particularly dangerous in refractor telescopes with multiple lenses in them such as an apo doublet or triplet. I never use any of my more expensive telescopes if the temperature is less than -15° Celsius. In cases where it is extremely cold, the pressure on the lenses or mirrors could possibly crack them, which would be a disaster in a more expensive telescope.
GREASE THICKENS IN THE COLD WEATHER
The pivoting points of most mounts are lubricated with grease- usually cheap grease. The colder it gets, the thicker the grease becomes. This can cause the mount to stick when you try to aim the telescope, and can also put enough strain on motor drives to make them run slower when you try to track or slew to a target.