My "Little Six Inch Fellow"

After a trip to the local library, my dreams of a half metre cassegrain dissolved fairly rapidly. I was advised by all and sundry to start with something manageable, say a six inch Newtonian.

I duly ordered a six inch pyrex mirror kit from Newport glass works, which arrived a good few months later, and started madly grinding. My target was f/5, as I reckoned that would be a little harder than the f/8 recommended for a first project, but still doable.

After much work in grinding and polishing, I then spent an enjoyable couple of weeks figuring the mirror, then sent it out for aluminising.

I built a fairly portable mount for the mirror, using purchased secondary, secondary mount, focuser and eyepieces. I've included a few photos of the mount below for reference.

Above is an overview shot. It's a shameless copy of Ronald Ravnebergs' "A scope like Alice". Although I've done as Ronald suggested and added a few of my own touches along the way.

The mirror box is 10mm "marine ply". The focuser board is 6mm MDF, and the rocker box is 16mm MDF. I bought the eyepiece (a nice 25mm Televue Plossl) as well as the focuser (JMI) and the secondary and secondary holder (Novak). Everything else I made, or else conned my wonderful workmates into making for me in their spare time.

The next photo shows a view down the barrel, as it were. The primary (yet to be coated at this stage) is sitting on a mirror cell (I am yet to make the mirror retaining clips) which is fabricated out of mild steel plate. A button headed cap screw in the middle of one plate provides a pivot point, and four screws on the sides allow the telescope to be collimated. The weight of the mirror cell was carefully calculated to counterbalance the secondary and focuser, despite the pivot point being fairly close to the primary.

The core of the design is the truss tubes. These are made out of two 25mm aluminium tubes I fished out of the scrap bin. The length of the shorter one (500mm) dictated much of the telescope design. A friend cut some 25mm holes in some blocks of aluminium for me on a lathe, and then cut them into cradle shaped bits, and I did the rest of the metalwork with a drill press, taps, files, and lots of work.

The spider is located with two simple stainless straps, which are bolted to a length of 19mm hex shaped aluminium bar (scrap bins are wonderful) which I drilled a 9.5mm hole in using the drill press.

The altitude bearing is made from pieces of 6mm delrin sheet, which work reasonably well with iron on plastic veneer, which I bought from the hardware store. Most of the woodwork is just glued and screwed together. My nice new router had plenty of work.

The object of this telescope is for it to be portable enough to carry on my motorcycle, as the seeing where I live is truly dreadful. By undoing four bolts, all the optics pack up to a package some 24 x 24 x 30 odd centimetres, as well as a pair of 50cm long aluminium tubes, which should fit nicely in my carrier bag.

The telescope is currently (June 2006) in pieces. After a 4km hike to the top of Mt Orroral with it, I'm rebuilding much of the mount to reduce the weight.