John Dobson started making telescopes from the portholes of ships. After the mirror is polished out it is placed vertically in a stand. More ambitious amateurs have been making mirrors in excess of 36 inches. March"Robert E. No matter how often the string is struck the frequency does not change. The telescope criteria calculator. Check out the four page story on my 25 inch and Pierre Lemay's new helical focuser in the February issue of Sky and Telescope magazine.
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Astronomical Society of Greater Hartford
In it I make the case for 'telescope mode' observing. The night of x power; when we ran out of doubly stacked barlows. More exotic materials can perform even better, but they can be unrealistically expensive. These had a large readership of enthusiast sometimes called " telescope nuts "  constructing their own instruments. Ordinary glass expands much more. The mirror is now being supported by the tool that was used to grind the back flat.