View Single Post
  #28  
Old 29-04-2012, 03:57 PM
madbadgalaxyman's Avatar
madbadgalaxyman (Robert)
Registered User

madbadgalaxyman is offline
 
Join Date: Mar 2011
Location: Brisbane
Posts: 936
Wavytone,

your comments about using only a 2-4 element eyepiece for certain applications are very very interesting and very worthwile;
though there are some experts who would regard these comments as being highly controversial or questionable.

This sort of argument lead to the idea of a "planetary eyepiece" designed, for instance, to maximize freedom from scattered light in the field that is caused by reflections from multiple air-glass surfaces. For instance, the planetary observers swear that a good orthoscopic eyepiece can give planetary views that are better than those provided by many of the more complex eyepieces.
(Planetary surfaces are a severe test for any combination of optical elements, as the slightest unwanted or excess light that is in the diffraction disk or in the field....can lead to a loss of low contrast detail)

I note, however, that maximizing the contrast between the object and the surrounding field, also can improve the observer's view of a deep sky object. On stellar and non-stellar deep sky objects, the particular Nagler eyepiece that I mentioned had considerably superior contrast to the LVW I tested, to such a large extent that the difference was blatantly obvious even after a few seconds viewing;
but exactly what combination of smaller star images and/or greater light transmission and/or a smaller amount of scattered light, was actually the cause of this noticeably better performance by the 20mm typeII Nagler..... I do not know.

cheers, bad galaxy man

Last edited by madbadgalaxyman; 29-04-2012 at 03:59 PM. Reason: typo
Reply With Quote