화성에 대비해서는 좀 늦은 감이 있지만,
미국의 Astro-Physics사와 러시아의 Aries사가 공동 개발한 아이피스 시제품이 나왔다고 합니다. 아래의 리뷰는 AP의 사장이 테스트한 결과를 유저그룹에 올린 글입니다.
팔은 안으로 굽는 다고 해서 자사 제품의 평이니 오죽 잘 했겠습니다만, 평소 그의 언행으로 보아 믿어도 손해는 없을 것으로 봅니다.
다만, 아직도 출시시기는 미정입니다.

아래 내용을 아주 간추려 이야기하면.....
시작품 5mm 8mm를 받아서 테스트 해 보았는데, 42도 화각에 38미리까지 퍼펙트한 상이고 아이릴리프도 아주 좋아 보기 편했다. 이제까지 본 아이피스 중에서 제일 좋았다. 죽음이다. 뭐 이렇습니다. ^^

Date: Thu, 26 Jun 2003 13:10:37 EDT
From: chris1011@aol.com
Subject: Eyepieces!! (Very long)

Hi all,

Today I received a package from Aries which contained 2 sets of our new
design planetary eyepieces - 3 pcs. 5mm and 3 pcs. 8mm. I was jumping up and down
as Marj handed me the package - we have been anxiously awaiting these lenses to
do a full evaluation on this new design.

As you might remember, I did test a 12mm version of our planetary eyepiece
design in Florida using the 10" Mak. Based on the evaluation tests that I did
down there, Valery of Aries Instruments and myself came up with a different
configuration to optimize the performance. Valery did the calculations to optimize
the design to increase the eye relief, and off-axis sharpness. The new design
features long eye relief and as wide a field as possible with tight sharp
star images across the field for all focal ratios from F14.6 (our 10" Mak-Cass)
down to F4.3 (for our 9.25" FastMax).

I spent most of the day evaluating the image performance of  these new
babies. After just a few minutes I knew without doubt that we had two outstanding
winners! The performance exceeded my expectations. I will describe the tests
below:

The test instrument was my trusty 130 F6 refractor aimed at an artificial
star source. For comparison, I have a set of new Zeiss Abbe Orthos for which
Baader was kind enough to send me the spot diagrams and theoretical off-axis
performance, so I knew what to expect as far as image sharpness, off-axis
astigmatism etc.

8mm field curvature and sharpness:
Using the 130F6 lens, the field is clean out to 38 degrees. With the
artificial star focused in the center, it remains a clean round Airy disc over the
entire field. You can see the central Airy disc and the diffraction rings right
up to the field stop! I have never seen that with any eyepiece with only 3, 4
or even 5 elements. Defocusing the star, the circular diffraction pattern
remains round to the edge of the field. The eyepiece shows almost no field
curvature that I could detect (the 130F6 has a tiny bit itself, but the eyepiece is a
very good match). Checking a 10mm Zeiss Abbe - this eyepiece has a 45 degree
field, but from 30 degree outward, the Airy disc shows typical cross shape of
astigmatism. Out of focus, the Abbe shows the typical oval shape of astigmatism
starting from about 30 degrees out to 45 degrees where it is quite oval. I
believe the new 8mm can have 42 degree field stop and still look better there
than the Abbe, however, vignetting will limit the field. Some experimentation
will be needed to find just the right size field stop.

8mm eye relief:
UnnnReal! This eyepiece has almost as much eye-relief as the 16mm Abbe! I can
see the entire field easily without my eyelashes coming even close to the top
of the lens barrel.

5mm field curvature and sharpness:
I like this eyepiece very much. It shows the same sharp Airy disc over the
entire 38 degree field. The field can probably be extended to 40 degrees for
this ocular, maybe 42 deg with slight vignetting. The Airy disc at focus is sharp
and hard, with excellent contrast. Comparing a 6mm Zeiss Abbe, the Abbe again
shows some off-axis astigmatism - a cross shaped Airy disc and oval shape out
of focus beginning at about 35 degree field size. The 6mm Abbe is somewhat
better than the 10mm Abbe, but again I feel that the 5mm triplet is sharper over
the same size apparent field.

5mm eye relief:
Excellent! Again, I can see the entire field of view with my eye well back
from the ocular barrel. The tip of my eyelashes are just barely touching the
barrel - almost the same as the 10mm Zeiss Abbe Ortho. With the 6mm Abbe Ortho,
my eyelashes are essentially squashed against the ocular barrel in order to see
the field.

Reflections - I can't see any. Will have to wait until full testing on the
sky.

Contrast - I would expect the contrast to be every bit as good as what I saw
down in Florida with the original 12mm, and perhaps a bit better since Valery
has improved the coatings on this set. In a side by side visual examination,
the coatings on the triplet oculars look almost identical to the Zeiss Abbes.

When it comes to optics, I have a very critical eye and can spot aberrations
in almost any optical system (my own included). I have seen a lot of
eyepieces, and there are precious few that can actually deliver diffraction limited
performance, both on axis and off, with short and long focal ratio telescopes. I
consider the Zeiss Abbe Ortho to be the standard for planetary eyepieces
(until now), however my criteria for a better eyepiece was that it be sharp over
the field with little or no astigmatism at the edges, and an order of magnitude
below the diffraction limit at focus. While the Abbe does not produce this at
F6, in fairness it was originally designed to work with the APQ refractors at
F8. I don't know of any Orthos that work truly well at F6 or below.

Just for comparison, I pulled out a couple of other "planetary" eyepieces.
While I cannot, and would not, compare the contrast using an artificial star, I
did test only the state of correction over the field. There was no contest -
they all failed in comparison!  A standard (and popular) Orthoscopic from Japan
showed about twice the astigmatism as the Abbe at the edge. I have a 6mm
Carton Orthoscopic that I always considered right up there with the best. No good
either - astigmatism starting half way out, culminating with a nice Maltese
cross at the field stop. Premium Plossl, 7.4mm, shows the same or slightly more
astigmatism with heavy vignetting starting at about 80% of the field. Just for
funsies, I tried an inexpensive Chinese made Plossl that someone told me was
pretty good. Oh my! This 35 degree apparent field eyepiece produced the most
mis-shaped edge stars that I have ever seen!

As a final test, I loaded up an 8mm Steinheil Monocentric triplet. This
design uses high index glass and was designed to be flat over a 25 degree field.
Yes indeed, the image was quite sharp over about 90% of the field, but then it
ran out of gas. In a classic monocentric (high index or low), the field can be
made very flat and reasonably sharp up to a critical angle, and then the
sagittal and tangental planes curve back very rapidly and the image diameter
mushrooms dramatically. In this eyepiece it happens at about 24 degree field size,
and the image deteriorated very rapidly at 26 - 28 degrees where vignetting
finally extinguished the light. Because of the small field, the overall
impression using this eyepiece was like looking through a drinking straw. Wider field
monocentrics can be designed, but then the field will not be as flat
(regardless of the use of high index glass), and some astigmatism will result toward the
outer part of the field because sagittal and tangential planes will not
coincide out there (same reason that the Orthos and Plossls produce cross shaped
astigmatism in the outer part of the field).

Bottom line:
These new designs are everything that I had hoped they would be. Superb
sharpness over the entire field, excellent eye relief combined with very high
contrast, works with my fastest refractors - everything I ever wanted in a new
super planetary eyepiece. In fact, I'm thinking of calling it a "SuperPlanetary"
eyepiece.

Thanks, Valery, for an excellent design! And thanks to your technicians who
labored on all the various prototypes for us, even staying at work during some
of your holiday times (give them a big kiss for me).

Roland Christen