This week, I'll address the size and type of your observatory. You'll need to take three considerations into account when considering your observatory's size. The first involves the available space. How big can you build? This was the limiting factor for my own observatory. Because I had to deal with a fenced-in backyard, my structure's maximum size was predetermined.
The number of telescopes is the second consideration. Most observatories house one permanent telescope. Others, however, contain one permanently mounted scope with space for at least one other telescope on a portable mount. In such a case, the observatory is bigger, but it's also more functional. For example, you could observe visually with one scope while imaging through the main instrument.
The third consideration related to observatory size is money. I know what you're thinking: Isn't cost always the first consideration? It isn't in this case because without dealing with the other factors first, you'll have no idea how much, even in general terms, the observatory will cost. I will discuss the cost of individual items in a later blog. Keep this in mind, though: While it's true larger observatories cost more, the cost-to-size ratio is not linear.
Beyond these initial considerations, probably the most personal decision related to your observatory will be choosing between a dome or a roll-off roof. First, consider the aesthetics. Non-astronomy people usually associate a traditional observatory building with a dome. This can be good or bad. The appearance of the dome may clash with its surroundings. Also, a dome can draw unwanted attention from people (primarily youth) with less-than-admirable intentions.
Domes are better at reducing stray light because only the slit is open to the sky. Roll-off roofs radiate trapped heat much more quickly. Domes will protect you better on windy nights. Roll-offs provide a more impressive vista of the sky from within.Zoning or planned-neighborhood ordinances may forbid the construction of a dome in some areas. This also works the other way. In one instance, a friend chose to build a dome because of existing tax laws. He did this to minimize the building's area coverage, upon which his city based taxes. In his location, the area covered by a roll-off roof when it was open also was subject to property taxes.
Next week, I'll get into the specifics about each type to help you decide.