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At some stage of my life (before our twins were born and I had a little more time) a former colleague and good friend of mine, Greg Roberts, got me interested in satellite tracking. In order to follow these sometimes feeble spots of light crossing the sky, I acquired an old 20x80 spotting scope which I mounted on a surveyor's tripod, alongside the original home-made finder from my 9" Astronomical Telescope. I also added setting circles to enable me to point the telescope along the expected track of the satellite, as predicted by computer software. A close-up of the telescope can be seen in the picture below.
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The telescope was originally fitted with an erecting prism for terrestrial use near the horizon, as can be seen in this picture on the left. This is not practical for satellite tracking where a comfortable viewing position of the Zenith is necessary. With a non-destructive modification, I changed this to a 90° eyepiece with the option of easily returning to the original system for terrestrial viewing. By using the same drawtube size as my 9" telescope, a low power eyepiece, yielding a more than 4 degree field, can be fitted - good enough for satellite tracking. In the picture below, the original spotting scope eyepiece can be seen, fitted to this 90° prism modification.
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The azimuth "bearing" is simply a hole in a round teflon piece, into which the rod of the azimuth mount fits (see the picture below). Around this teflon piece fits the azimuth setting circle which is formed by a 360° plastic protractor which can be locked by a thumbscrew in a any position. |
| This azimuth rod was originally part of the steering mechanism of a motor car which was modified with a 90° bend, yielding enough overhang for the scope to reach the Zenith. The other end of this steering rod ended in an eye which became the altitude bearing. |  |
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Another plastic protractor completes the altitude setting circle. To set up the mount, the tripod is first levelled w.r.t. the azimuth bearing top surface. After mounting the telescope, it is pointed at a known object. The azimuth circle is now rotated until it reads this position and locked in place. The altitude pointing is automatically OK when the tripod is level. By using my ASTRO program, this known object can be any astronomical object. This can be great fun when used to find planets and bright stars in daytime. |
| The home-made finder telescope was made from an old slide projector lens after simply adding an eyepiece, yielding an effective 7x50 monocular. The original spiral focus mechanism of the slide projector is very handy for focussing by moving the objective lens instead of the eyepiece. A finder is not essential for satellite viewing but is sometimes found handy when trying to find a relatively bright satellite using old elements when a wide field of view is ideal. |  |
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All the different components of the finder and main telescope with the two prism options can be seen here, spread out, in this picture. |
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