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The mounting was designed to keep the eyepiece at a comfortable height so that I don't have to bend over while hunting. It is very stable despite its unconventional appearance. The top half is a standard Dobsonian design and is supported by a pier which sits on top of a car jack. This allows me to raise or lower the scope by small amounts. The front legs are held together by a chain and eye hook arrangement. Having an adjustable base makes it possible to set it up on a sloping surface. My dark sky site south of Canberra is on graded dirt road with a pronounced dip at the shoulder. The centre of the road is quite flat, but curiously, I don't like to set up there! |
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The scope is controlled by a custom built DSC program known as Real-Time Observer. The laptop is kept warm in a light tight box with a sliding lid. The box has a false bottom which contains the power supply and AC inverter. Most components are already plugged together. When setting up on-site, the remaining leads are plugged in through holes covered with heavy duty rubber. As they are always in the same position, I can do this in the dark while my dark adaptation begins. An 80Ah deep cycle battery powers the DSN control box and laptop. |
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Detachable 8K encoders are mounted on the altitude and azimuth bearings.
For smooth motion in azimuth, I have used a 12" diameter "lazy
Susan" bearing. It can be pushed with only slight pressure from one finger.
The altitude bearings ride on pads made from a substance known as "Lubron"
which is similar to Teflon. The surface was roughed up with with a file
so that the motion in altitude is quite stiff. This means that the scope
won't accidentally change altitude as I rest my hand on the end of the
tube while scanning in azimuth. Many thanks to Keith Ward for machining
the encoder couplings.
The DSN control box monitors the shaft encoder positions more than 50,000 times per second. It accumulates the encoder positions and communicates them to the Real-Time Observer software over a serial link. |