Ptolemy's Cafe

Lessons Learned

What I Would Do Differently Next Time

Westward Ho!
I had to make it roll off to the west to avoid messing up my yard too much. But this is a more serious compromise than I thought. I'm loosing too much of the western sky, which is my darkest (though the seeing is usually poor that low). This problem is especially severe for the western pier location. There are a couple possible solutions other than the obvious rolling off to the north. First would be to make the roof peak lower. Second would be to make the rails longer so the roof could be pushed farther away. Third would be to have roll off rails on the eastern side, too. This never occured to me until long after it was too late; I had just assumed that they would be way to ugly to be over the deck. But not so! They actually look kind of neat (IMHO).
Newts need not apply
The high walls make are much more of a problem for a Dobsonian than an SCT or a refractor. I designed it with my LX200 in mind. But when I try to use my 10" f/6 Dob inside the observatory its lower optical axis means that the top of the walls is much higher in the sky. An equatorially mounted Newtonian would either have the same problem or would necessitate the use of a ladder to reach the eyepiece. A really big Dob would also need more floor space. Looks like my next scope will have to be a refractor :-)
We get a lot of wind here. And as I was raised in San Diego, 50 degrees F and a 15 mph wind seems like an arctic blizzard to me. The walls, high though they are, don't protect from the wind as much as I would like. A dome looks a lot better when I'm shivering and going back in for my ski suit in May! A dome was out of the question this time but next time I think a roll off dome might be the way to go. Or possibly a split roll off (roof rolls two ways, joining in the middle with the possiblity of each half going past center) so that the opening could be adjusted to fit the weather.
More isn't always better
My concrete pier is unnecessarily big. All that extra mass didn't seem to have any effect. Strength is not much of an issue with amateur scopes. What is important is vibration damping. Concrete isn't good at that. My huge pier is not harmful but it's not helping much, either.
Room to roam
Even though it came out bigger than planned, the floor area could be a little bigger. There's no room to pass between the scope and the wall if the observing chair is in the way. Another two feet in each direction would help. (Assuming the two scope layout; with just one scope in the middle I think it would be fine.)

Bill Arnett
last updated: 2000 Oct 10