Friday, February 10, 2012

Cloudy day exercise: motorizing a Maksutov

First, I've to find a place where I can mount a motor.  The screws at the back were for collimation, and so I cannot use them.  The whole focuser shaft is a moving part, so I cannot fix it there.  I might use the visual back but then it's a bit crowded there.  So I've chosen to install a plastic plate via the dovetail bar.  It's a great fit since I use a file to fit in exactly, the plate is fixed via the mounting screw of the dovetail to the OTA.

The original owner has installed a timing pulley there on the focuser shaft but the screw was a little bit too long so that it has to be tightened excessively in order to engage the pulley, so I've installed a plastic ring to make it an easy fix.

So you see the plastic plate and the timing pulley installed.  On the other size you can see the Rigel Quick Finder base installed via the threaded hole originally for a finder.

The first proof-of-the-concept prototype was done by using blue tack and a simple rubber band, backlash is crazy but then it works.

On searching my tool boxes, I found a thin belt which should work better than a rubber band, and then I also fixed the motor via some metal wire...  I should find a thicker belt and a better mounting method in the long run, anyway, this is how it looks like:

 Finally a short video to see how it works out:

The whole setup costs nothing, since I have all the parts at home.  The most expensive part is the DC geared motor while the plastic plate, the pulley and the belt were all very cheap.  The hand controller is from my JMI NGF-CM focuser, so it's shared with no additional cost.


Further improvements:

I wanted the whole setup to be removable and can be placed back easily, so I've enlarged the mounting screw hole to a slot so that the whole thing could be taken out easily.

The above pictures tell the whole story easily, the big white pulley was left on the focuser shaft to serve as an oversize focusing knob.

No comments: