Re: 1.25" TV plossl vs other 2"
- From: mmd49@xxxxxxxxx (Mark D)
- Date: Sun, 17 Jul 2005 07:31:19 -0600
Hi Zarkovic,
In essence, a 32mm eyepiece regardless of whether it is 1-1/4", or 2"
will give the same image size, and magnification, so in all actuality,
the appearance of an object will appear identical, all other things
being equal.
The only differences that will be noted, will be the larger actual field
of view, due to the larger diamter lens elements, and the larger
diameter eyepiece barrel.
Due to not doing my homework on these other eyepieces you mention,
(sorry) I cannot comment on what types of design they are, how they
perform, and whether they are Plossls, Kellners, or ?
While the Plossl is said to be a simple design with generally two
cemeted symmetrical doublets, it is commonly known to be a superior
design to the Huygens, Ramsden, and Kellner designs.
As an example, years ago, I once bought a relatively inexpensive $300 or
so 2" eyepiece (I forget the brand name at the moment) from a fellow
amateur, and it was said to be a less expensive Japanese copy of the
revered, and awesome 2" 30mm 88 degree Leitz, which at that time was
commanding a price of about $1400-$1600.
While it looked nice, and bore some physical resemblence to the Leitz,
it was not a very good eyepiece I'm afraid, and was certainly not
anything near in performace to the 30mm Leitz.
Through my 105mm F-5.8 AP Traveler, much Coma around the outer 1/2 of
FOV, and nasty false color were noted.
Through a longer focal length instrument, such as my 5.2" F-12 Apomax
refractor, it didn't perform too badly, but a scope such as the Apomax
with its long focal length have the ability to make eyepieces such as
cheap Huygens, Kellners, and Ramsdens perform almost like they were
world class Carl Zeiss Abbe Orthos, or Clave Plossls.
Fast focal length scopes place a heavy demand on certain eyepiece
designs., and some may not be up to the task of performing all that well
at FL's of F-6, and faster.
I quickly sold the imitation Leitz, as to me, it didn't make sense
keeping an eyepiece that only performed OK in just one instrument of
mine.
Let it be noted also, that there were a few intinerations of the famed
30mm Leitz, and I understand that one intineration was NOT a very good
performer at fast focal lengths, and was designed to work well with
scopes generally F-10 or longer.
I'm hoping others can comment about these other eyepieces you have your
eye on, and just how well they perform in thier own personal scopes.
Mark D.
.
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