Northamptonshire Natural History Society

Astronomy Section

Section President
Nick Hewitt
Section Secretary
James Whinfrey

Godfrey Finn's telescope

After reading many books, and seeking advice from experienced astronomers in the NNHS, my son Nicholas and I considered various options, and finally decided to build a Newtonian reflector on a Dobsonian mount.

The Hourglass Nebula taken by the Hubble Space Telescope

The optics were purchased, but the rest of the instrument was constructed by ourselves. The octagonal tube is made of 9-mm ply with 20-gauge formed aluminium angle fixed inside, and the box mount is also made of 9-mm ply. The mirror cell is made of 19-mm MDF, stiffened for stability, and is mounted at three points round the edge - one of them a universal joint, and the other two on strong spring-tensioned mounts. Two collimating rods enable adjustments from the top of the tube. The diagonal mirror is on a three-arm curving mount.

These and other metal parts were made by my son-in-law Stuart. A strong triangular base was constructed, and the turntable is fitted with a two-way spirit level, rotating in azimuth on three fixed castors. Turned trunnions are fitted inside sections of 7-inch gas-pipe to facilitate altitude adjustment. Setting circles are also fitted, and we use the StarTrak program on a hand-held Psion 3. The tube splits into halves, and the box hinges to fold flat, so that the entire instrument can be dismantled to fit into a car.

Image credits: Stellarium (background image)

Menu credits: http://javascript-array.com/

26 May 2014 (v 22)

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