advice pitfalls on self build newt

[graham.hobart (Graham stevens)]

Hello, sometime next year I am interested in a self build project-either an f4 12" newt or f5 10" -depending on mirror availability.
I want it to fit in my dome so would have to be max length about 1100mm and have a sturdy probably moonlite focuser.
This could be a truss design as my friend El Draco is building a huge Truss currently and I am hoping to pick his knowledge !
Weight limit would be scope and camera plus smaller scope (SV 60 frac) on PMX.
I am looking at suggestions for mirrors, for fittings, for design inspiration and for any pitfalls.
I have a basic ATM book and have seen the NEWT WEB design app (which doesn't seem to work on my laptop).
This is really to get more personal satisfaction than buying a bigger scope as I really like my 8" newt and a 12" f4 that had a small footprint would be about the best I could do in my dome. (and still slew it!!)
I know this is a brad ranging enquiry but I thought I would test the waters early to avoid financial mistakes.
Cheers
Graham

[ZeroID (Brent)]

I'd suggest you check out Rolf's (Skyviking) website with his 12" Serrurier truss design and his earlier 10" f5. I've 'copied' his design principles twice now for a 10" f5 and an 8" F8 and it builds a strong, rigid and well balanced OTA. The rest comes down to build accuracy.

[AlexN]

I'm using his design idea at the moment in construction of an 8" f/4 and rebuilding my 5" f/5 too. I'm doing the mods mostly because I find the tubes of commercial newts let the optics down. My 8", the tube creaks when slewing from east to west even with the rings 13" apart and no extra weight. (no cameras etc) and I've done the same test with the laser collimator in the focuser and saw the collimation shift between east and west.

[glend (Glen)]

Check out my 10" f5 carbon tube strut imaging newt build thread in the ATM section here.

[AlexN]

I've been reading through it the past few days Glen. Very nice indeed. I only worry I will fail to get the alignment of the focuser right.

[glend (Glen)]

If your building an imaging newt the Newt Design apps are schewed to visual design and not camera image spot size and location, so keep that in mind. As to focuser location, make some drawings, mock up a jig that allows you to slide the focuser to find the optimum position, only then build the final location. Good luck.

[AlexN]

I'm basically taking the measurements off the ota as it stands at the moment with regard to secondary and focuser position. Just locating the central frame based on balance. Just doing calculations I dont think I can easily truss convert my 5" with where the balance point is already. It's focuser/camera end heavy to the point where the front ring is hard up against the back of the focuser.. I really need to make the rear end heavier to better the system and by measurements I've made the rear will shed weight and the front end won't really at all. That's a bit of a shame as I would have liked to have done a test of concept on the 5" before doing the 8"