by The Bolton Group
Homemade GOTO mount - shown with C8 tube
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A Poor Man's Paramount
by The Bolton Group Homemade GOTO mount - shown with C8 tube |
 Advantage of the German mount - different tubes can be mounted
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Introduction It's red & black, it has Byers gears, it has GOTO....but is it a Paramount? Definitely not! But at slighly less cost (1/10th) it is our answer to a computer controlled German mount. It uses AWR's stepper motor GOTO drive system. This British alternative has periodic error correction and the ability to interface with Planetarium software such as SkyMap. It will however function without a computer and the latest version of the software has in-built object databases (see later).The Mount The mount is over 20 years old but is built to carry a massive load. It features solid steel shafts, 2 inch diameter for the RA and 1.5 inch for the DEC plus oversize ballbearings. The castings are aluminium. It was updated with new Byers worm gears - 7.5 inch 360 teeth for the RA and 4.7 inch 359 teeth for the DEC. The 7.5 inch gears were made to upgrade SCTs. The smaller gears were made for the CamTrak. Brian made the new gear mountings and clutches. Both worm mountings have adjusters so the mesh between the worm and wheel can be finely adjusted. Conventional wisdom is that you don't have clutches on GOTO mounts. Common sense says you do! It anything should go wrong - and remember in the dark things do - they could save your gear teeth. To minimise backlash (the killer for GOTO mounts) the stepper motors are coupled direct to the the end of the worm shafts. It has periodic error correction using a infrared index switch and a disk with a slot attached to the worm shaft. The mount has now been set up im its permanent home in the Yorkshire Dales. The polar alignment has been carried out using the AWR two star calibration method which returns the alt and az errors making homing in on the pole relatively straight forward. Residual errors were 0.01 degrees in both alt and az. The latest vesrion of the AWR software was installed 2005. This has provided comprehensive databases (no planets yet). I had a few teething problems with this upgrade - it has a few new parameters to enter which are zero by default and until they are changed the mount declares most objects below the horizon. The periodic error correction recording was also lost and has to re re-entered. I do this with a webcam now and IRIS software rather than looking through an eyepiece at an illuminated reticule. |
 Byers gears to both axes - note direct drive from motors to worm shafts
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