Re: ATM Enhanced coatings

[epabcc@epa.ericsson.se (Bratislav Curcic)]

Larry Manuel wrote :

> coronographs [the instrument used for viewing the corona of the
> sun, with an occulting disc] are always made with uncoated objectives [which
> are lenses] since the coatings scatter more light than an uncoated surface

> If I'm wrong, please correct me.

Yes, you are wrong (and I was too)! Apparently, there is a coronograph in the
orbit that is all reflective, and it uses special method of ion "wind" during
aluminizing to get super smooth coatings. It is unlikely that your favourite 
coating company would have the technology, though.

> Perhaps a Huygens, Ramsden, Monocentric or Tolles type could be made to work
> astoundingly well, in a long f/ratio scope, without coatings.  The level of
> polish on the surfaces is more critical than the coatings in a simple
> planetary eyepiece, I believe.

I can't agree more !!! Not just those, there are some old Zeiss uncoated Orthos
around that are worth their weight in gold. Ortho, unlike Plossl, has very steep
surfaces, so reflections are much less noticeable. So it's not just guys with 
long refractors and Schiefspieglers that can enjoy these.

But all that said, many modern eyepieces are just as good (if not better),
despite multicoatings. Especially fancy glass ones (ED etc.).

Bratislav