Big Dobs are great

Anybody know of an observatory design which accommodates big Dobs say 9/10
feet high. OK runoff roofs is one but it leaves everything very open to
wind etc There must be some new revevolutionary thinking out there.
I am not as impervious to cold and discomfort as I used to be.....

"Kerr's Pink" wrote in message ...
Anybody know of an observatory design which accommodates big Dobs say 9/10
feet high. OK runoff roofs is one but it leaves everything very open to
wind etc There must be some new revevolutionary thinking out there.
I am not as impervious to cold and discomfort as I used to be.....

You will find that a closed observatory has to be just as cold as
a open observatory. Otherwise, the temperature difference will distort
the wavefront as it encounters the air bubble at the opening of the
observatory. The best one can do is to limit wind exposure.

Modern dome observatories have the ability to move massive amounts
of air at low velocity. The opening of the dome may be 30% dome
diameter, and a large part of the base ring can be opened to allow
unfettered airflow. This provides rapid cooldown. Observatories
designed to be used nightly, will air condition the interior air to
the expected twilight temperature surrounding the telescope to further
minimize temperature equilabration.

A big DOB is not an ideal design for a dome. When the altitude bearing
is located at mid tube, the size of the dome is minimized. Modern
DOBs have altitude pivot points around 20% scope height. This will
require a dome of about 2*(DOB_Height*(1-20%)+1ft), or for a 10ft
DOB 18 foot dome, while a scope balanced at 50% height could use a
12 ft dome (maybe even 11ft).

Mitch