Telescope Reviews: Post a picture of your refractors (PART 5)

After dinner tonight I went out to my observatory (in my driveway) and fired up the 1500 watt heater under the seat. The temperature in Minneapolis tonight is about 12F, the air is crisp and we have Jupiter and a first quarter moon overhead. This should be a good night for a bit of cosmic cruising.
After I finish this post I’ll take my thermos filled with hot apple cider out there where the inside temperature will be around 68F. I’ll be out there till 2 or 3 AM. I’ve been known to fall asleep leaning on the eyepiece. Later, when I quit for the night and look in a mirror, I see I have a black eye from the rubber cup on the eyepiece. None of my astronomy buddies can make that statement.
Per the invitation for observatory pictures I offer some shots of Tardis I, my heated observatory. It’s home built, started in 1980 and finished in 89. The scope was built around a rugged 6 inch F-10 Jaegers that I bought for $350 in 1978. By rugged I mean it has not had a lens cover on it for the last 18 years. The objective is always marinated in the outside ambient air so no problem with heat currents. No need to temperature stabilize, it’s always ready to go.
The 1500 watt heater, can hold an inside temp of 65F with the outside temp as low as -20F. In use for nearly 23 years I remember only once when I had an image problem due to inside heat. During a “star party” with a group of 8 year olds, Jupiter looked like a jiggling ball of jelly and I was befuddled by the cause. With young people hanging on the eyepiece inside and several more waiting on the entry stair with the door open I realized what the problem was. I told those standing to get off, and shut the door. I’ve never had a problem with heat since.
A feature of my design is the layout of the mounting. It shares some resemblance to the Naysmith design with some large differences. I use the term asymmetric alt/az to describe the Tardis I mounting. The significant word is “asymmetric”. Simply stated, asymmetry allows that for any object in the sky there are two possible positions for the scope (objective lens) to view a given object. One position places the objective up wind of the heated cabin and the other downwind. The objective lens can almost always be positioned up wind in virgin outside air. Heat rising up from the enclosure is drawn down wind, away from the objective. I must admit, although I believe the above is true, I have never had to consider “upwind or downwind” while viewing. Heat rising has never been a problem with viewing. Keep in mind, the enclosure is well insulated.
At 81 years old, I can be up and running in two minutes flat. (same to shut down). Last week we had our first snow for the season here in Mpls. We received 17 inches (see photo) and I did use a broom today. I’m not into fancy observing (high tech stuff), I just enjoy “cosmic cruising”.
Cheers,
billybird

Edited by billybird (12/22/12 01:38 AM)