Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Lawrence Sayre
Abbe Normal
Reged: 10/16/04
Posts: 4731
Loc: N.E. Ohio
|
Re: Strange Results in Eyepiece FOV Comparisons
05/17/08 07:26 AM
|
|
|
In addition to accounting for the rectilinear distortion present within the eyepiece, the RFOV also corrects for the field of view modifying effects of the "real" focal length of an eyepiece as opposed to the focal length under which it is marketed (and upon which it is stamped). I believe this is why Baader's AFOV (actually RFOV) figures for the Eudiascopics are so far off from Orion's 52 degree AFOV for the Ultrascopics. The Eudiascopic (and Ultrascopic) eyepieces not only have inherent pincushion, but their focal lengths are also likely not as indicated (being in all instances somewhat less than indicated). This also could be a significant factor for the Hyperions TFOV vs. AFOV. Ditto for the Ethos. If in fact the Ethos exhibits noticeable pincushion of greater than about 1.7%, then its real focal length is likely not 13 mm.
People have often wondered why the pseudo-Masuyama's from Celestron (the original Ultima's) were sold as for example 12.5 mm, 18 mm, and 24 mm, whereas the others all sell them as 15 mm, 20 mm, and 25 mm respectively. Hmmm??? 
--------------------
My philosophy, in essence, is the concept of man as a moral being, with his own happiness as the moral purpose of his life, with productive achievement as his noblest activity, and reason as his only absolute.
Ayn Rand (in the appendix to 'Atlas Shrugged')
|
|
6 registered and 11 anonymous users are browsing this forum.
Moderator: Greg K., Jason B, csa/montana
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Rating:
Thread views: 1772
|
|
|
|
|
|
|
Previous
Index
Next
Flat
Edit
Reply
Quote
