Quote:
Originally Posted by tnott
A friend of mine got rid of curved vanes in his scope because he reckoned they changed shape with change in temperature, throwing out his collimation (like a thermostat?).
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I've not really ever seen this happening on any curved vane spiders that I've actually had the pleasure of using. I could possibly see this happening if he'd used two dissimilar metals, which have wildly different coefficients of expansion. Phil here has used brass/brass - so they should be thermally "centred". Even if they were dissimilar, because they are in a spiral pattern, each on a third, I'd expect them to all contract or expand at the same rate each, still resulting in a centered secondary.
If one vane was bent the opposite way to the other two (i.e. the dissimilar metal strips were accidently reversed on one arm) then maybe... Anyone??