Quote:Consider the use of fibreglass resin (like polyester resin) - mix it up, brush it on. Your cardboard tube will no longer be cardboard, it'll be a composite of cardboard and polyester and so will be waterproof, rigid, etc... It cures in 30-90 minutes, so let it set up until it's no longer tacky and then gently tease the rings into place to ensure the round shape is there, but not mounting the rings in permanently. You may be able to buy aluminium tubing of even PVC plumbing pipe with an appropriate internal/external diameter, but if you've found something that fits, go with it. Call it a prototype and no-one can say nothing! Not speaking from experience - I've not made a sight tube like this, but just some ideas for you. Good luck.
Celestron 8SE Dobstuff 13.1": Swayze refigured Coulter mirror, 6 pt mirror cell (2 pt edge support) and CF focuser board made by me StarBlast 4.5 ST80/PortaMount II Zhumell 20x80/Oberwerk 15x70 on a Seronik-style tripod boom mount Hubble Optics 18 inch F/4 mirror.
Quote:so it should be sufficient to squarte the secondary under the focuser? another quick question; i have a laser coll and coll cap, so do i need a cheshire?
Quote:I know it sounds silly at first but hear me out. I want to use a cardboard paper towel tube to make a sight tube. I found out that a m42 t adapter fits perfectly in the end of the tube, making it 100% perfectly round. I also found out that the retaining ring from a m48 filter fits perfetly around it, allowing it to be screwed to a 2 - 1.25 adapter and making the other end perfectly round. Stick a collimation cap in the adapter, verify everything is level, and you have yourself a pretty much free sight tube. I have an idea to use string for the crosshairs as well if the sight tube part works. Is that a silly idea or do you guys think it could work? Advice would be very appreciated as I don't really want to spend 100 dollars on a sight tube, thanks.
Ron NS11GPS Pronto
16" dob Vixen NA140SS
127mm F9 Surplus Shed/Crawmach kit scope
Best of ATM