Ye Olde Telescope Tubes...

[boomboom]

Just thinking out loud here.
An idea based on Tim's great refractor and an attempt to reduce weight of my 6" f12 Istar atm Frac.





The pics are of the dew shield that I cut more than 1 kg of weight off by cutting the tube into a skeleton and riveting .5mm thick sheet on. Hopefully the internal skeleton structure is visible.

If I did the same thing with the 1460mm long OTA would it flex, be as strong as the solid 3mm tube? From memory the OTA weighs 6-7 kg's.

It depends a bit on how much metal is left on the solid tube to some extent. is there any rule of thumb for this sort of thing? If I could take out a couple of kg's off I'd be happy

Design wise along Tim's refractor, lots of rivets..... a whole lot actually!

I will try and sketch the skeleton idea, scan it and add it.

As I see it...

Pro's Look really good and reduce weight.
Con's might flex

Thoughts?

Matt

[Mike]

I would just switch over to a thinner walled aluminum tube. We are doing the same thing with our scopes. Going to much thinner walled aluminum tubes, smaller lighter weight counter cells, back plates and tube rings have reduced the overall weight dramatically. Our new tubes will use .032" (.81mm) thin walled aluminum.

[boomboom]

.81mm…..WOW that is much thinner than my 3mm.

I can't find a tube that thin which is why I thought of redoing mine.

.81mm…..for my tube that would be the equivalent to 2kgs instead of 6kg!

Seems like I should just go ahead and get another tube and chop it to bits and see what happens. Honestly this ATM thing is so cheap I can't think why more people are not into it. Well I do know….lack of time, tools, a bit of know how, which isn't my problem.

Think I'll give it a go and post as I go along.

Setting up the scope the other day I wondered how many years I had left to raise a 16Kg scope to shoulder height and get it in the saddle without dropping it or giving myself some kind of back injury….oohh for a permanent setup!

Seems like I can remove quite a bit of tube material before it wobbles about?

All I need is an Aluminium blade for my power saw.

Matt

[ploughc]

Mike will the thinner walled tubes still hold the lens cell firm
with no flexing of the longer focal length telescopes.

Pat.

[Mike]

Yes, absolutely. At this point the longest tube we will be making is the 150mm F10 and 204mm F9. All 150-12's are now made in the Truss format. Since the Asteria 150-12 TCR performs better than a 150-15 in terms of CA, we have stopped making the 150-15 OTA. The 150-15 is impractical to ship because of the length of the box at 102 inches. We will still make the 150-15 lenses for the ATMers. So again in answering your question since the longest tube we will be making is a 150-10 the new tubing is more than adequate. We have also added another baffle which adds to the rigidity and overall balance. We have also "lightened" up the entire assembly quite a bit which will put less stress on the tube.