Finding a tube supplier for a refractor.

[Guest chaz2b]

I’m having trouble trying to find a supplier of tubes for refractors. I have a Astro-Tech 102ED objective cell and a Starlight featherlight focuser which I wrote about in another board a little while ago, I was pointed to Moonraker telescopes, but they are a little out of my price range.

Does anyone know of a supplier or maker that I can contact? Or did you find your own solution?

 

chaz

[vlaiv]

How about making your own?

I don't think it should be too hard to do. Maybe trickiest part will be flocking and baffling the tube, otherwise, you can get aluminum tubing of required diameter fairly cheaply and it would take just a bit of machining to get it in shape?

 

[Guest chaz2b]

Actually I have bought a Ali tube of near dimensions, but I would have to have an adapter machined for the cell to fit, the focuser is slightly smaller than the tube so again an adapter to give a snug fit, I could then use JB weld to fit the two, using a release agent on the threads of the focuser so I can remove it or adjust the focal length.

When it comes to collimating,  it will require me to be pretty accurate ensuring the parts are perpendicular to minimise collimating the optics.

 I also bought flocking a little while back for a 10” dobsonian which I haven’t got round to, but flocking a smallish tube will be a challenge for my big hands!

The only other thing will be a suitable material for baffles and knowing where to place them, is there any links to refractor construction?

chaz

[cletrac1922]

Chaz

Seems a lot of effort, for something which might not work

Machining is not cheap these days, and had to be exact

Be interested to see finished result

John

 

[vlaiv]

56 minutes ago, chaz2b said:

Actually I have bought a Ali tube of near dimensions, but I would have to have an adapter machined for the cell to fit, the focuser is slightly smaller than the tube so again an adapter to give a snug fit, I could then use JB weld to fit the two, using a release agent on the threads of the focuser so I can remove it or adjust the focal length.

When it comes to collimating,  it will require me to be pretty accurate ensuring the parts are perpendicular to minimise collimating the optics.

 I also bought flocking a little while back for a 10” dobsonian which I haven’t got round to, but flocking a smallish tube will be a challenge for my big hands!

The only other thing will be a suitable material for baffles and knowing where to place them, is there any links to refractor construction?

chaz

Maybe simplest thing to do would be to get a section of tubing that is a bit smaller diameter than main tube.

Then you can cut a thread in main tube, and cut outer thread on smaller diameter tube (machine it to fit inner diameter) - and fashion adapters for focuser and lens cell out of this?

Don't know what is the best way to go about collimation - maybe just make sure that your cuts are straight and perpendicular to tube and also be precise when drilling holes?

As for baffles - well, you want couple of those and you also need to know what is usable field from that lens, and then it's the matter of just drawing the diagram.

You can make a scale diagram on a piece of paper and measure diameter of each baffle (and position) or you can do the math (a bit of trig) to get exact values. I can do a simple diagram that will help you understand what is involved.

[Guest chaz2b]

Well it all sounds very straight forward, but it will require extreme accuracy for me to get the best out of the Astro-Tech objective.

 I find it annoying that those who sell these items cannot get replacement parts.

The cost of a complete scope is $599 from astronomic, so getting any machining done needs for the costs to be kept at a minimum for it to be worthwhile project.

The alternative is to find postal/carpet tubes of suitable diameters and then glass cloth them.

chaz

[GlenM]

The trouble these days seems to be finding a little jobbing shop that would do the machining for you. Could also turn out pricey. I used to buy my aluminium tube for aluminium warehouse. 

 

Glen.

 

[Guest chaz2b]

Came across I R Poyser how to build a telescope, very informative.

chaz

[johninderby]

The aluminum tube is the easy bit to obtain. When I built my Carton 100 f13 scope I made most parts myself but had the countercell machined by Richard at Skylight Telescopes.

Protostar flockboard was ideal for flocking the inside and also for making the baffles. Search ray tracing for baffles for info on getting the baffling right. Many use powdercoating for the tube which is cheap but nowhere near as tough as proper two pack paint but that cost several times as much to have done.

https://stargazerslounge.com/topic/319262-carton-100-f13-reborn-return-of-big-red/

 

Edited June 25, 2019 by johninderby