Re: (IAAC) FWD: What should I buy? (rich field scopes)

>Certain facts still remain. The transmission of a good ortho is more than
>that of a Nagler. (Al says so, on this I am prepared to believe him. I have
>never measured it, but I could easily do so if anyone has any interest.)
>The Nagler cannot, therefore, be "brighter".

>Jeff Medkeff          | Acting Assistant Coordinator

I speak for myself Jeff but I am interested in the transmission data
comparing 4-elements orthos and 8-elements naglers (as well as other commun
eyepiece designs). I have a friend here in France who has already measured
transmission curves of nebula filters for me and I believe he could do the
same with eyepieces to evaluate their rough transmission but if you have
the data already, I think it would be interesting as a starting point (I
have the theoretical data given from ligh loss per air-glass surface
variying on the type of coatings and the number of air-glass surfaces, but
practical data may be slightly different, who knows...).
I guess rough overall transmission of an eyepiece gives indications about
reflected light (ie indirect clues to scatterings, ghosts images, ...).
From my own data, I am inclined to agree with you that the best orthos are
more "transparent" to light than naglers (and Meade UWA 4000...) as long as
all are fully multicoated on every optical surfaces, but I would like to
know if the middle prices orthos (those not fully multicoated or just
simple coated) can compete with the same naglers/UWA regarding only the
transmission factor (putting aside distortions, astigmatism and coma.) ?

clear skies, Yann.

PS: I am very proud of myself today because I understood at least what the
discussion spread acronyms BTW and OTOH meant (beeing a natural born
english speaker really help on the net...).

Yann Pothier	tel: 01 43 41 43 29
11 impasse Canart, 75012 PARIS, FRANCE
Email: ypothier@abi.snv.jussieu.fr
Site : http://pegase.unice.fr/~skylink/publi/cielextreme