Truss Refractor?

[LAW (Murphy)]

I should preface this by saying "I have no idea what I'm doing".

I have a Tasco 525 that I bought for $10 to use as a guide scope but my SSAG won't mount straight onto the .96" focuser and the tube is too short to mount it straight on with the focuser removed.

So I looked around the garage to see how I could overcome this problem, and I saw a lathe and a camp chair...

My plan is to use the aluminium legs off the camp chair between two rings with the lens mounted at one end and a 1.25" clamp for the camera at the other. The 'tube' needs to be 565mm long plus 135mm for the eyepiece holder to make up the 700mm focal length.

I chose this method to overcome the diameter differences between the 67mm lens and the 51mm clamp and I can always wrap it in carbon or aluminium if there's too much stray light getting in.

I drew this up on a napkin at the cafe this morning so I'm sure there's something I've overlooked, any suggestions are most welcome.

[2stroke (Jay)]

Most people just grab some pvc for the finder scope conversions, really you should go a .965 to 1 1/4 and use an extension tube but hey thats money. I wouldn't use a truss setup though sounds to dodgy, just get pvc white and match it up nice. this may give you some idea's

http://www.cloudynights.com/ubbthrea.../o/all/fpart/1

and here
http://msfastro.net/articles/finder_guidescope/

[alistairsam]

if the aperture is small, I wouldn't bother with a truss, it may not be effective at small diameters, plus all those connectors would be tiny.
best to fabricate a pvc or wood extension with the focuser removed and then tape the ssag to the fitting.
although I've always wondered what a truss refractor would look like, just having built a truss reflector.!
Something like the Hubble's main body with multiple sections might work.
scroll down this amazing site to see the hubble truss frame
http://www.apollomissionphotos.com/i...le_hubble.html

[MattT]

Here is the Istar prototype truss refractor.
http://istarscopeclub.proboards.com/...lay&thread=318
Matt

[LAW (Murphy)]

That's cool! I haven't had a chance to fire up the lathe (little cousins running around waiting for Santa).

Hopefully mine will look something like that, I had a similar plan for a baffle tube at the camera end so I'm glad I'm not the only 'mad' one around

It's more of a curiosity thing now to be honest, depending on how it pans out I may use it as an opportunity to test some fabrication techniques for my main OTA project.