Re: [ATM] PLOP Calculations

[Andy Saulietis <iss@pvtnetworks.net>]

Nils Olof writes,


>You have a point there, but here's how I think about it:
>If you could position the sling at the right level (of the COG) and
>accurately parallel to the mirror back, it would be ideal. But if you can't
>exactly (and I believe most mirror boxes won't let you do it easily), you
>could either:
>1) position the cable accurately at the mirror (by clamp or friction) and
>have the cable/sling leave at some small angle, pulling the mirror edge
>forward/back *or*

The 37" will be collimated by tilting the entire primary complete
with its cell so maintaining the location of the sling should
not be a problem.

>2) letting the cable (with bearings) roll against the mirror edge and find
>its own best position - perhaps a little away from the exact level of the
>COG, but without any grip on the mirror edge.
>
>I believe 1) is much more at risk for astigmatism, which is why I prefer to
>keep close to alternative 2).

I'm a little leery of letting the sling find its own preferred
position..I'd at least have non-contacting guides to limit the
excursion.

>The whole problem of edge support has received less attention than the back
>support, unfairly I think, but there is a wide open field for designing and
>experimenting.

I agree. Some of these problems have already been solved by the
pros, like mercury or air bag edge flotation, using a cetral perforation
for the edge support (done this & it works), etc.


>I have just made a quick-and-dirty webpage about my ideas for a 3-part
>sling - see:
>http://w1.411.telia.com/~u41105032/sling/threepart.htm

Interesting..I'll have to think about this.





Andy Saulietis
ISS Enterprises
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