Quote:
Originally Posted by FabrizioF
about ausastronomer: "The Pentax XW's, which use multi layer partial phase coatings, have a transmission > 90% across the entire visible spectrum; and in the critical range from 500 nm to 620 nm they achieve almost 95% light transmission (96% @ 550 nm [green light])."
But....this is the transmission for each single optical surface, correct? It means a light loss of 4-5% x each optical surface, I suppose. I cannot belive the light comes out from the eyepiece with a total of 5% light loss. (if you say YES  I will buy some XW just tomorrow!!!).
Cheers
Fabrizio  |
Hi Fabrizio,
The figues I have quoted are the "net" transmission figures for the entire eyepiece. The top quality multi element widefields with modern glass types and coating technology will all achieve 92% to 96% "net" transmission for the entire eyepiece. These include the new Televue ETHOS and DELOS, The 12.5mm Docter (possibly the best eyepiece I have ever used) and the Nikon NAV HW's. Despite what you might read on Cloudy Nights, I don't think the older Televue eyepieces (earlier Naglers and Panoptics) are quite up to the newer offferings in terms of ligth transmission and contrast.
Cheers,
John B