[APML] Focus

[Stuart Heggie <stuart.j.heggie@sympatico.ca>]

Just got to try my new focusing tool. It is an STI IV ronchi grating. I
just used the part with the grating (i.e. straight through) on my long
lens. The focusing went according to the textbooks - lots of lines down
to essentially all black then all white as the star drifted across the
grating (I had the drive off).

A couple of questions:
My lens has an internal skylight filter and a front objective filter (to
protect the lens). The determined focus is quite far from the marked
infinity point on the lens (not unexpected as a lot of my pics are
ruined by soft, bloated stars). Is it possible that the two filters are
shifting the focus this much? They are both skylight filters. The
internal filter came with the lens and I left it in - the external
filter I bought to protect the objective.

Second, anyone willing  to offer a pronunciation for "ronchi" so I don't
sound like a goof if I ever talk to anyone about these?

Thanks!
Stuart

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