The NexStar User's Guide - Excerpt from Chapter 8
Cold Weather Gear for Your Scope
Cold weather is not friendly to an electronically controlled telescope. If you resisted buying a large rechargeable power source, you will discover that your little AA batteries run out of juice even faster in cold weather. An AC adapter or other good power source is a necessity in winter weather.
Additionally, the LCD panel on the hand control becomes sluggish and even illegible in cold weather. If it isn't too cold, you can slow down the rate for the scrolling information using the 1, 4, and 7 buttons as described in Chapter 5. But when the temperature really drops, your hand control needs some heat to operate normally. If you are already using the Kendrick or DewBuster dew prevention systems, Kendrick makes a heater element for hand controls. The Kendrick TelRad heater element also works well for hand controls. Another option are chemical hand warmers available from most outdoor equipment suppliers. Attach one to the back of the hand control with elastic.
If your hand control is past warranty and you are handy with a soldering iron, another solution is to mount two small resistors inside the hand control. Power for these mini heaters comes from the hand control itself. Visit the Astro Articles page at Matthias Bopp's web site (http://www.dd1us.de) and read the article for the N5/8 or the N5i/8i electronic hand control heater.
While dew can be a problem other times of the year, frost will form on optics in the winter. Powered dew prevention strips discussed earlier are your best defense against frost.