Taking Care of Schmidt-Cassegrain Telescopes

Video Transcript

"There is one drawback to using this type of design. If you're out on a cold night you tend to get frost forming on the plate or, in some cases, you can get a pretty good layer of ice forming on it. So, there's a couple ways you can counteract this. My favorite type is what's called a dew zapper. You can purchase these at pretty much any telescope store or any place that sells telescope accessories. All it is is just a bunch of little resistive heaters. You take this band, you just wrap it around the front of the telescope and you plug it in to some sort of power supply that has a cigarette outlet, and over the course of the night, this band will gradually heat that plate to where it's just a few degrees above ambient. But it's enough to keep frost and dew from forming on it. Now, if you happen to be in a location where you do have access to power and you don't happen to have one of these dew zappers, you can just get a hair dryer and, basically, warm the plate over the course of a few minutes, just to where it's a few degrees above ambient. And, you want to be careful not to hold the hairdryer very close or else you may end up thermally shocking the glass and, in that case, it might shatter. You'll notice that, over the course of time, you might get dust or fingerprints on the plate. And your first inclination may be just to take any type of cloth and start rubbing until you see that dust and those fingerprints disappear. That's a bad idea because, you may not be able to see it, but there are special coating on this glass that allow light to pass through it more easily, and they're called transmission coatings. If you use any old type of cloth or cleaning solution, then you may end up actually removing a lot of that transmission coating and that's going to end up degrading the quality of your image. So, one type of cloth that I often use is, it's called a lints cleaning cloth. These can be purchased at any optics store, any camera store. They often come with binoculars or even telescopes. And these are safe to use on the glass, they won't scratch the coatings and they won't scratch the glass."