Quote:
Originally Posted by alistairsam
Thats looking "schmick" Rolf.
With the 4 UTA supports, do you think they're adequate to prevent any lateral movements?
I've found that the weight of the secondary mirror exerted sufficient force on the strings to flex or move the upper part of the UTA, sufficient to show deflection with a laser.
I therefore added two rectangular ply pieces along the x and y axes. that strengthened it a lot. I'm wondering if it'll be more pronounced with yours as the focuser woud be quite heavy and when the scope is at say 45deg, the upper ring might show some deflection due to the mirror and focuser's weight.
Could the Al tube bite into the ply underneath over a period of time due to the lateral forces?
Also with the washers underneath the guitar head holders, wouldn't that allow them to swivel as the bolt is at one end?
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Thanks Alistair
I haven't noticed any movement with my current 10" which is built with the same 4 poles, but it's certainly a possibility to add some ply pieces to prevent movement if I see any. I don't have a laser collimator but plan to get one and then I'll be able to test how it holds up while moving the OTA around.
Re the guitar tuners, that was exactly why I added the washer - to make it easier to swivel them
I found that the orientation of mine are quire hard to adjust when the wood is screwed down together without a washer, you sort of have to break them loose again if you even need to adjust the direction of the strings. I had to do that once when I replaced the secondary and re-stringed the spider. Now with washers underneath I expect the holders to be easier to swivel, and no it doesn't move at all when it's tightened.
I thought about adding some mechanism to adjust this angle with some screws but that would add extra weight so I didn't.
Quote:
Originally Posted by ausastronomer
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You actually want it to bite in a fraction. If you use a good quality hardwood plywood it will only bite in less than .5mm. This is just enough to give the spreader poles grip on the plywood so there is no lateral movement in the top end at all. You should use aluminium spreader poles with a wall thickness of .9mm.
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Cheers John, that's exactly what I did. The poles are sitting tight up against the plywood and they do indeed make a circular mark and bite a little into the surface. Should be secure I think.