Quote:
Originally Posted by FabrizioF
I want to be optimistic: the light transmission of each optical surface can be 95% so for each single surface it means a light loss of 5%, extreme optimistic: 2%??? it means an eight elements eyepiece=10%-40% of light dispersion, more: each surface gives another problem, the internal reflection=lost of definition on bright images (planets for example), this is why refractors or some reflectors are best for planetary images (not catadipotrics). In terms of magnitude it is easy to say: your main optics-(10%-40% of light grasp)= true main optics aperture.   |
Modern "multi element" eyepieces with newer glass types and multilayer coatings can do notably better than this. 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]).
Whilst the Clave Plossls are very good, they are also very warm in their colour tone (coffee colour) and are the complete opposite to the Zeiss orthos and Brandons in this regard. Although the warm tone does help with some planetary observations, notably on Jupiter; it is something I really don't like much, particularly on the moon.
Cheers,
John B