Hello,
about this lense, how good would this make a LX with SD-11 clear for
astrophotopgrahy ? equivalent of this would be 5.8" mirror Smith
Cassegrain. and a 24x36mm eye-piece...
what type of TC could be used with this lense ?
Philippe
> Hi,
>
> a question to the optical-formula gurus. Pentax describes the optics of
> this mirror lens as 6 elements in 4 groups. Looking at the diagram that
> they provide us, I see 8 elements. I will number them 1 through 8 when
> looking from left to right. 1 and 2 as well as 5 and 6 seem to be forming
> the two two-element groups (like the optical formula suggests), but what
> about the rest?
>
> I am thinking like this:
>
> - elements 2 and 3 must be mirrors, so they might not be counted towards
> the number of optical elements. Now we are down to 6 elements which
> agrees with Pentax. But the number of groups is now 5.
> - alternatively, element 8 is the screw-on filter, so that might not be
> counted. Then we are left with 7-5. Still doesn's fit.
>
> Your ideas are welcome. Cheers,
> Boz
>
> -
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