Removing any condensation

There can generally be two places where condensation can be a problem and these are the telescope objectives and the imaging camera (particularly where a large ccd chip is involved). The telescope is easier to resolve and this can be done with either or both dew shields and dew heaters. With regard to the telescope the larger the objective the more the problem is likely to occur so a dew shield may not be sufficient on its own in which case a dew strap should be wrapped around the tube assembly roughly where the main objective is, what level of dew control you use will depend on the size of the objective and the level of humidity in the air, you want just enough heat to get rid of condensation but not so much as to introduce air currents inside the dew shield.

The camera can be a trickier problem but several solutions are available depending on the camera manufacturer and the understanding of your girlfriend/wife. Some of the SBIG range have a dessicant cell in the camera housing which keeps the ccd chip enclosure dry, the cell needs to be removed periodically and 'cooked' to dry it out before replacing it back in the housing. FLI have a more permanent method whereby the ccd chip housing is hermetically sealed and it contains an inert gas which prevents moisture from permeating and building up. Some other manufacturers such as Artemis have started to introduce heaters for the camera window. I use Starlight Xpress which doesn't use any of these methods and in cold damp weather condensation on the camera window and ccd chip are a problem when the camera is switched on. This is where the understanding of your spouse comes in as I borrow my girlfriends hair drier. I detatch the camera and use the hairdrier at an angle to the optical window until all condensation on the window and ccd chip has disappeared. Following this it is important to check that no contaminants have ended up on the optical window otherwise these will show up as strange shaped dust doughnuts on your images. I always do this just after it has got dark with a red light as this shows up any contaminants better, I use an air gun to remove these, again at an angle to the optical window.

Now the camera can be connected back up and I am now ready to focus.