The poles
look thin, but if they are carbon fibre (or even aluminium) then the stiffness may be fine. Causes of problems are often different to what we might first think. When I first built the 16" tridob lots of people thought the poles were too thin (20mm Aluminium) but they were plenty rigid enough for the light UTA.
There were issues with the secondary going out of collimation, but it was due the wire spider exerting torsional force on the top ring. The design I used was a X-cross section though, rather than a V-shape like this one-so you wouldn't get the same "seesaw" effect on the top ring. Also, there was too much space between the apices of the poles and the attachment points of my spider. I had to stiffen the top ring but afterwards it was all OK.
In my subsequent scopes I made sure the spider attachment points corresponded to the apices of the poles for better structural stiffness and so learnt from my mistake.
This design is different and I am interested, if the secondary is going out of collimation, where the flexure is to help others in their future ATM choices.
I've admired Bruce's scopes before and drew inspiration from them. It is interesting to see how much big scopes can be cut down without suffering from poor performance.
PS - wire spiders don't need to be under a lot of tension.
, not specifically to this design but others I've seen - where the secondary is held in place by a 'wire' based spider, how is it arranged so that the secondary holder-assembly doesn't "bounce around", if you get my drift....there must be quite a bit of tension in the wires to stop that from happening which in turn would mean the secondary frame has to be pretty sturdy to stop it from warping...
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to the forum Bruce.
