Fun with lenses and mirrors!

Some years ago I bought an achromatic 6" F8 refractor. They were on special from Celestron as an introductory offer and impressed with the size of the aperture and the stories of what I'd be able to see with it, I took the plunge.

So the thing arrives and it's massive. It has a serious hunk of glass at the front. My previous scope was a little a 60mm refractor from some years before, but this monster could eat scopes like that for breakfast. I put it together and it looks like a howitser. The supplied aluminium tripod's not really up to the job, so I replace that with an old surveyor tripod, read up on equatorial mounts (just enough to get myself into trouble) and reckon I'm ready for some serious skygazing...

Four years later and the scope's been gathering dust in a corner for most of that time.
I think this is what happens with many a store bought telescope or those gifted during christmas. They look impressive in the shops, they have little signs saying '300x magnification!', there's spectacular astronomy pictures on the wall (taken with much larger, professional level telescopes), but once you get your little unit home, you realise just how user unfriendly hobby telescopes actually are.

Consider - it's dark. You have a long tube you're trying to point at one tiny point in the sky. The mount works on odd axes. The finderscope typically doesn't have a diagonal, so you have to scrunch your face up close to the main tube just to look through it. Many objects are too dim to be seen through the finderscope and so you have to equate a book of starcharts with what you're seeing in the night sky- not at all easy for a beginner. For extra fun, you should use red light to retain your night vision when reading your charts and the image in the finderscope is usually upside-down. Sigh. Perhaps your dimwit neighbour steps outside and wonders if he should call the police when he sees you sitting next to what appears to be a rocket launcher, poring over flightpath charts with a stealth nightlight.

The mosquitoes make a meal of you or it's bitterly cold and once you think you're pointed in the right direction, you transfer your attention to the main eyepiece. Success? But the earth keeps turning and by the time you've gotten focus and searched a little bit, your attempts have lost you the prize. So it's back to the finderscope just to verify your aim. And don't touch the eyepiece! Else the seeing will vibrate like a moth caught in a spiders web. And don't breathe - you may fog the lens. And scrunch up your other eye because it's one eye viewing only. As a rule, the eyepiece will always be at an awkward height and if you haven't strained your neck and back by the end of the evening you just aren't trying hard enough!

It's no wonder Trademe.co.nz is doing a good swap in secondhand scopes. Let this be a warning to those who think owning a scope will be 'neat' and a 'gateway to a new world'. Well, perhaps a very uncomfortable one.

So 'm going to do a crazy bad experiment. I want something I can take outside and just plonk down on a table. I want the eyepiece to be at a comfortable height regardless of the scope's pitch. I want up/down/left/right pointing - because equatorial movement is just too much work.I want to use that big hunk of glass I've got, but I have absolutely no woodworking skills and only limited access to tools (I might be able to drill a hole or two). I don't want to spend too much money (like buy a goto mount) and I want to use what I've got plus a few bits and pieces I might get over Trademe. It's going to be a hobby project. Sounds impossible?

Well, I've ordered a cheapo 6" short focus reflector. Basically, I'm going to take it to bits and shove the refractor's big objective lens on the front. It will be the bastard child of a newtonian reflector and traditional refractor a 'fractonian' The theory is that the objective mirror will not only fold the objective len's lightpath back on itself, it will also shorten its focal length. This should allow me to reposition the diagonal at the tube's centre of gravity (pitch point), meaning the eyepiece will not move when the tube is pitched up or down. I'm also trying to source a cheap dobsonian mount and will try and jury rig it all together. I expect it'll be an abomination - but it'll be interesting and I'll see what happens. ;-)