Grasslands Observatory - Essays - Observatories: The Good, The Bad, & The Ugly

II. THE CHOICE BETWEEN OBSERVATORY AVAILABILITY and OPTIMAL OBSERVING CONDITIONS; DESIGN FOR SEEING

Most amateurs live in or near an urban environment and have to contend with light pollution and light trespass. Unless you can afford the luxury of having more than one observatory, one of your first choices is where to put it--in or out of town (see ASTRONOMY November 1989, page 93). An in town location near your home has the advantage of ready availability usually at the sacrifice of dark sky conditions. Out of town has the advantage of a dark site at the sacrifice of convenience.

It is mandatory to select a site that has as good seeing as possible, because consistently poor seeing will severely detract from your viewing whether you are looking at the moon, planets, double stars, or deep sky objects. Seeing is the most overlooked considerations in selecting a site and in designing an observatory. Don't make this mistake! Even if you are going to build a small structure in your backyard, determine the location that gives the best seeing.

Be sure to construct your observatory with materials that produce the least thermal disruption. It is critical to avoid heat buildup (see Telescope Making #33, page 8). Concrete block and brick buildings absorb heat all day long and radiate it all night long. Asphalt walkways and parking lots next to the observatory are particularly destructive with heat waves coming up for hours. This shimmering in front of the telescope can ruin even low power images. Also, a dome with a small opening which does not allow for ready escape of heat will create a chimney effect at the dome opening.

Roll-off roofs observatories are easier to build than domed observatories. They allow more rapid heat dissipation, and they also allow you to view the entire expanse of the night sky. If you plan to regularly have large groups visit your observatory, remember that only one person can look through the telescope at one time, and only a few persons can crowd around a CRT monitor to look at CCD images. It can get rather boring for everyone else standing around in a dark building. With a roll-off roof observatory, while one person is using the telescope, everyone else can enjoy a naked eye view of the sky, scan the sky with binoculars, or even set up another small telescope in the building.

BACK | NEXT