Retrofiting 10" QCPTA telescope - 3

[Chanlunlun]

Dear ATMs,

While it is the topmost priority to repair the most important component, the primary mirror, of the 10 inch telescope the weather suddenly went worse. According to the Hong Kong observatory cold weather will persist for one week. A sudden drop in temperature prohibited the use of pitch lap to refigure the primary mirror.

We are not planning to sit there doing nothing. As an alternative we took up the job of re-engineering the gearbox of the slow motion control motor of the declination axis. This gearbox was originally made with plastic gears from 4WD toy motor cars and designed to reduce the speed of the stepper motor by 5 times. However the output shaft of the gear head was soon proved to be still running too fast and for a long time we had been thinking to re-construct this gearbox. This job was finally done on yesterday ( Saturday, 29th Jan,2005) , after a delaying of 4 years.

The job included an addition of a second gear train to reduce the speed for another 5 times to slow down the motion of the output shaft. As we also wished to save as much money as possible we decided to work on the existing gearbox instead of building a new one. This required drilling new holes accurately on the existing housing, machining new spindle and very precise assembling of new gears to the existing ones so that they can run without troubles. One careless mistake will spoil the whole gearbox. Fortunately the job was finished on Saturday without accidents.

It was this re-engineering of the gearbox that will make the equatorial mount boost in performance. I am delighted each time I see this gearbox displayed.

Best regards
Chan Yuk Lun
30-1-2005