30+inch+TROK+Telescope+construction

__Dave Owens images of the TROK__
http://picasaweb.google.com/daveowen1956/TROK30

The TROK mount and tube was mostly modified hardware from the old TRO telescope. The main parts salvaged and modified were the rocket box, mirror box, and top end cage.

The main parts that had to be made from scratch were the azimuth bearing, altitude bearings, mirror support, spider and secondary holder. Some images below show the construction of the telescope back in 2002.

The original TRO rocket box was too high. I used a router to lower the sides for the new larger altitude bearings. The old altitude bearings were too small. New ones were cut out with a router and lightweighted. 3 x 3/4 inch ply layers were used. The old TRO secondary had a 6.5 inch minor axis as it was F4. This was too large for the new F6 mirror. A new secondary was purchased instead of making it. A new spider and holder were made. The spider is now a 4 vane spider for greater rigidity. The original 3 vane spider is shown below.

The telescope needs 3 x 20Kg weights for altitude balance. These are easily removed for transport and stored in the floor of the trailer. A new altitude bearing was made. We have found through trial and error that wax is not very efficient and increases teh stiction of the bearings in both azimuth and altitude. Instead we have found spray PTFE to be the best. The teflon bearings are 'faceted' to aid in reducing stiction. Thi seems to work very well. The TROK during first assembly in the garage. Note that the top end fixings to the cage have changed from 8 to 4 fixings in the lower images. This make set up much easier. One person can do it.


 * __30 inch TROK mirror support__**



We use a 27 point wiffle tree made of wood (3/4 ply) for the primary mirror support. This is still working well today (2008) without any maintenace required.

A strap is used for lateral support. This can be adjusted form the rear. Doube sided tape is used to stop teh strap falling off in transport.

3 large safety clips are used to prevent the mirror bouncing out while in the trailer. We thought that thsi may be a big problem, but we installed a wireless camera in teh trailer with a light to 'watch' the mirror as we drove and went over bumps. What it showed was that the mirror hardly moves at all. No damage to date has been seen, and I have been over some very big bumps and cattle grids!


 * __PLOP results for the 27 point support for the 30 inch F6 TROK mirror

__**



Images below show the telescope is assembled outside for the first time. A bottle jack is used to lift the telescope a few inches to remove and install the wheels for transport into the trailer. An aluminum bracket is provided mid way along the rocker box on both sides for the jack to lockate.

A 6 inch F4 telescope (made by Geoff) is used as a finder. Since these images were taken we have fitted Azimuth and Altitude setting circles. We can normaly point the telescope to within 1/4 degree (mostly in the field or on the edge). Dave Owen reads off the coordinates from his palm computer.