Paper Telescope Tube

[Karls48 (Karl)]

Few weeks ago I purchased 136mm x 457mm f 3.4 triplet lens cell that come out of some sort of document projector. I was thinking to build nice refractor telescope with it. Since I have been advised that this type of lens is not suitable for telescope.
I have tried it on bright terrestrial objects with 2’’ 30mm eyepiece and it doesn’t seem to have any false colour and image is sharp. I have already build mandrel to use 1.5 mm plywood to build telescope tube. But 1.5mm marine plywood is $ 85 and I don’t want to throw good money after bad. Question is has any one build telescope tube from old paper and how did you do it. When I was kid (that’s very long time ago) we used to build model boats from old newspapers, laminating paper on clay form. But I cannot remember how we did it. Would the resin-laminated paper work for a telescope tube? I don’t want to use fibreglass, I hate working with it and the cost would be about same as using plywood.

[xelasnave]

Karl I have used newspaper and flour for so many projects I can not remember them all... Make up what you have in mind and paint it with resin... fibre glass is the stuff the plastic (resin) sits upon ... I make stuff in cardboard and cover it with resin...it is now plastic.

Build something in balsa and resin it and man it is so strong...

Carbon fibre , paper, fibre glass it is something to hang the plastic on.

Get a tin of resin and hardener and try it out ...I have made parts for dishwashers out of cardboard for example...

If you want strength lay some fly screen in the inside of the tube and resin it...

Imagine the boats you used to build if they had a layer of resin...

alex

[Karls48 (Karl)]

Thanks Alex, when I read your reply and you mention flour suddenly I remember what we used for making model boats – starch. I suppose flour will do as it contains starch. I will have go at it and see how it will come up.

[bojan]

Paper is excellent material for telescope tubes. Of course, you need to soak it with some resin to protect it from humidity, like shelack or plyester or epoxy (araldite).
Before you try to make your own. try to get a tube from places selling carpets or cloth for tapestry etc...
They are very round and straight...

[jjjnettie (Jeanette)]

Ponders has a refractor made with the same sort of lens.
It was mounted within plastic downpipe. Looks good, works well.

[skeltz (Rob)]

first of all what are you going to use the scope for?
Visual or astro photography ?
i presume you are getting the ply from brims, if money is a problem do it the cheapest ,if not go brimsply they make the best stuff period...

[Karls48 (Karl)]

Mostly for astro photography, if it is any good. Lens cell is bit heavy at about 3kg. I have build mandrel for the tube, similar to what you have built for your big tube. Only I used 12mm dowels instead. Tube needs to be just 400mm long, but only 137mm diameter. I’m not sure if I can bend the ply to such a small diameter. Also good quality marine ply, they sell it as big sheet. No one wants to sell me 1200mm x 900mm sheet. That’s why I’m thinking to build it from paper.

[Glenhuon (Bill)]

Karl, at 136mm and short focal length I'd be more inclined to go for a piece of 150mm PVC pipe. It comes in various wall thicknesses and would be much lighter and easier to cut to length with square ends than a sealed paper tube.
Check out the various fittings available for PVC pipe, as I've found that there's always something that has the right inside or outside diameter to suit the mount of the lens you have. Be less work and cheaper in the long run too as your dealing with standard sizes.
Take the lens into Bunnings or similar and wander through the fittings/pipe section, ask for help too. You get some funny looks at the beginning, but then lots of help when the staff person get interested in the project

Cheers
Bill