3" F/4.5 Copyscope temporarily mounted on my camera tripod..

The view down the business end of this small scope.
The lens cell was mounted in the 4" PVC male coupling by wrapping it with tape and friction fitting it inside the coupling. The tape was trimmed so that it would not slip out through the hole in the front, and a 4" PVC double female coupling was put in place to form the telescope tube. I then used a 4" to 2" flush adapter to serve as the telescope end and focuser mount. Another 4" coupling could probably be added if you wished to utilize 2" eyepieces, but I added several pieces of drain tube extensions with set screws mounted in them to form a basic 1.25" push-pull focuser. 

A star diagonal is necessary to use this telescope without back pain. I have recently made one out of a 90 degree PVC Elbow, and an old binocular prism. It seems to work very well, but it is not the best mounting job I have ever done. If it does not work out, I may put the prisms back in the binocular body and attempt to make the entire telescope into what I had originally intended; a 3" binocular telescope. (just to be weird!) I would have to purchase another lens to do this.

Just a quick hint for those of you who try to make your own diagonal, always make sure the prism or mirror is perfectly aligned. It is very critical to avoid blurred and astigmatic images which are amplified by a scope of this type. I used double-sided tape and cork gasket material to fill the space and mount the prism.  I am very happy with the results of this diagonal so far, but I accidentally left off a screw to hold the eyepiece in. I have my eyepieces parfocalized with washers so that all they do is drop in to the correct position.

If this telescope didn't weigh about 20 lbs it would make a great finder for my 6" newtonian. It is so packed full of large, thick, glass lenses it is very heavy. I am currently building a wooden fork mount for it since it is way to heavy for the tripod.

Sorta' like a big telephoto lens on steroids isn't it?

Questions or comments?

I would have preferred an F/8 lens, but this was all that I could find on the market in my price range. Of course you can always splurge and buy a large format camera lens for the same effect, just be aware that F factors below 4 show serious uncorrectable coma in their images. The lens I used still shows coma around the edges at moderate powers and requires quite a good eyepiece at low power to straighten this out. It will give your eyepieces quite a workout, so I don't recommend building one this focal length unless you have several good eyepieces already.

Amazingly, my Rini 52mm eyepiece is absolutely wonderful in this thing with a dark sky. I get almost a 5 degree field of view with no coma, though the magnification factor is a bit too low at 4X. So I built a 30mm Erfle from a kit I purchased for $9.50 from Surplus Shed. It shows a little coma, but it is quite usable. A 35 to 40mm would probably be perfect.

I have bought several items from Surplus Shed and have yet to have any serious problems. Sure, occasionally I have received surplus lenses which were a bit more surplus than I cared for, but for 3-5 bucks a piece who cares! If you are creative, it is possible to make some really outstanding eyepieces with their eyepiece kits. I recommend sticking with the longer focal length sets at first since it is much harder to build small focal length eyepieces properly. They are also the dealer for Paul Rini's wonderful line of homemade eyepieces at VERY reasonable prices.