ANTARES 8.5-12mm
SPEERS WALER
VARIABLE FOCAL
LENGTH EYEPIECE
Available from various dealers: MSRP:
$299 U.S.
Once
in a while, an eyepiece comes along which kind of stands out as both a decent performer
and a bargain in price. In about 2003, a friend of mine put an unusually tall rather
odd-looking eyepiece in my hands for review: the 5-8mm Speers Waler. It quickly
became one of my favorite eyepieces, and its performance earned it the nick-name,
“The Canadian Cannon”. Now, Glen Speers and Antares have
come out with a new longer-focal length version, the 8.5-12mm Speers Waler Variable
Focal Length eyepiece. With it comes a lot of the performance seen with the 5-8mm
model at somewhat lower magnifications.
OK, so what's a SPEERS WALER??
The eyepiece WALER part of the name stands for
Wide
Angle
Long
Eye
Relief, and the concept
is a wide-field (over 70 degrees) fairly well corrected eyepiece. The variable focal
length comes from the introduction of the ability to move the field-flattening “Smyth”
lens in the front of the eyepiece farther away from the other elements. As such,
this movement acts somewhat like a variable power Barlow to raise or lower the magnification
while still providing much of the field flattening effect which is needed for these
better-corrected wide-field designs. However, these eyepieces are clearly
not zooms, in that in order
to use them at the various focal lengths, one has to refocus significantly, something
which usually is not necessary with a true zoom. Also, the apparent field of view
of the variable Speers Walers does
not change significantly with
the changing focal length, which is also considerably different from the way many
true zoom eyepieces behave.
The 8.5-12mm S.W.
: Even though it is only an 1.25-inch barrel eyepiece, the unit itself is a fairly
large beast, as many wider-field oculars tend to be. It is about six inches (153mm)
long at the 12mm focal length (including the installed rubber eye-cup), and grows
to a whopping eight inches (203mm) at the 8.5mm setting. Its maximum diameter is
about 2.5 inches (64mm), and much of its length is a cylindrical upper portion about
four inches long that is coated with a knurled rubber exterior to provide a good
gripping surface. This new baby really feels SOLID, as it is made of heavy thick
walled (3/16”) aluminum. This shows up in the 1.32 lb weight (600 g)
of the eyepiece, especially when compared to my old
5-8mm's less-hefty 480 gram mass and somewhat smaller physical dimensions.
The lower sliding section holding the movable Smyth
lens is just under 2 inches in diameter, and appears to be black-anodized aluminum.
It moves entirely inside the main body when at the 12mm focal length setting. The
original 5-8mm model used a long open narrow slit and a set screw to create a sliding
arrangement and lock for the eyepiece's effective focal length settings. This had
the potential to let external light and dust into the eyepiece. However, in the
new 8.5-12mm model, this problem has been eliminated. The slot is smaller and is
covered by the rubber hand grip and a thin flexible metal strip “spring”
with an inward-facing pin on the end. The spring pushes the pin inward into depressed
divots located on the outside of the sliding section, creating seven detent-like
“click-stop” positions of focal length selections of from 8.5mm to 12mm.
The focal length can be read off from a small oval window opening in the base of
the knurled body section, and the slide moves easily from stop to stop. One can
adjust the focal length to locations between the stops, but it can sometimes be
difficult to get it to stay there. The bottom of the sliding section also contains
the 1.25 inch chromed barrel base, which has the usual 8mm-wide “safety groove”
to help keep the eyepiece from falling out of some focusers or diagonals. The barrel
is also threaded for standard 1.25” filters, and I had no trouble in threading
mine into the eyepiece. It might have been nice to have the bottom of the eyepiece
set up as a “dual” 1.25”/2” barrel system, but perhaps that
was not possible given the mechanical needs of the variable focal length system.
Optically, the 8.5-12mm has eight elements (one less
than the 5-8mm model), and all are mounted securely with no rattling heard when
the eyepiece was shaken. The field “Smyth” lens is about 27mm in diameter,
while the eye lens is about 30mm across. All lens surfaces appear to be well coated
optically. The outer surface of the eye lens appears to be nearly flat, so I recommend
that the rubber eye cup be left on to keep external light from bouncing off the
lens and into your eye. Indeed, the eye cup is difficult to remove and sticks up
about 8 mm above the eye lens housing ring (it can be easily rolled-down however).
The eyepiece caps mated well with the eyepiece, with the eye lens cap diameter made
specifically to cover the rubber eye cup snugly. Antares provided a bolt case for
the eyepiece as well.
I tested the 8.5-12mm Speers Waler in my 100mm f/6 refractor,
my friend's 8 inch f/5 Newtonian, and my 9.25 inch f/10 Schmidt-Cassegrain. I also
compared it to both a 10mm Plossl and my 2003 vintage 5-8 mm Speers Waler. I did
star-drift timings using the refractor to determine true fields of view for three
of the seven focal length settings. I used these figures to determine equivalent
“effective”
field stop diameters, so that those considering the eyepiece for purchase will be
able to figure the true fields of view they might get in their own instruments using
the standard Field Stop formula: TFOV = 57.3*EFSD/Fl (EFSD is the eyepiece field
stop diameter and Fl is the telescope focal length). I also put the eyepiece on
my crude version of an optical bench to get a fairly reliable figure for its apparent
field of view, and used an artificial star to judge star image quality across the
field. Here are the basic eyepiece specifications:
Dimensions:
6 to 8 inches (152 mm to 203 mm) long x 2.5 inches (64 mm) wide.
Focuser
Barrel Size: 1.25 inch standard (threaded
for filters).
Weight:
1.32 lbs (600 grams)
Number
of Elements: 8
Focal
Length Stops: 8.5mm, 9mm, 9.5mm, 10mm,
10.6mm, 11.3mm and 12mm.
Measured
Apparent Field of View: 81.4 degrees
(constant at all focal lengths).
Eye
Relief: approx. 11 mm.
Effective
Field Stop Diameters: 14.9 mm
at the 12mm focal length setting,
13.4 mm
at the 10mm focal length setting,
11.5 mm
at the 8.5mm focal length setting.
Performance in the Field:
Overall, the 8.5-12 mm Speers Waler is a good wide-field eyepiece, with many of
the same advantages and characteristics that the early 5-8mm version showed. The
wide 81.4 degree apparent field of view was definitely appreciated, especially when
working the “high-power” end of deep-sky observing. Its ability to give
the user a range of focal lengths rather than only one allow the view to be more
precisely “tailored” to the object. I particularly appreciate this ability
when viewing objects like smaller open clusters, globular clusters and planetary
nebulae.
Optically,
the 8.5-12mm isn't quite equal to a Nagler, but it is definitely better than some
of the less-complex “budget” wide-field eyepieces that are commonly
available. The eyepiece was fairly free of internal reflections and ghosting, as
it took an extremely bright concentrated light source against a dark background
to generate a rather faint greenish ghost image of the source. Star images over
much of the field of view are quite sharp and of reasonably high contrast for a
multi-element wider field eyepiece. However, 11mm the eye relief is somewhat limited
(not exactly what I would consider “long”), making observing with glasses
difficult. Indeed, I had to push my eye into the eye cup a little just to see the
field edge clearly. Still, the eye relief was longer than that of many eyepieces
of similar focal lengths.
Most
of the common aberrations present in eyepieces are fairly well controlled in the
8.5-12mm Speers Waler. The dominant aberration was mild outer-field astigmatism,
which just begins to show itself beyond 75% of the radius of the apparent field
but is somewhat noticeable right next to the field edge (a bit more noticeable at
shorter f/ratios). Chromatic aberration is corrected quite well (better than in
the original 5-8mm version), with only the very slightest hint of lateral color
on very bright stars that are right next to the very edge of the field. I noted
no significant curvature of field, although a small amount could have been masked
at the field edge by the astigmatism. There is also a mild amount of pin-cushion
distortion present, along with the slight “blackout” effect when I moved
my eye out of the optimal position (another good reason to use the rubber eye guard).
Saturn
at 276x in the 9.25 inch SCT showed good contrast with even faint Enceladus being
visible when the seeing settled down. Indeed, the throughput of the eyepiece on
deep-sky was pretty good even in a relatively small aperture. After making a star-transit
timing, just for fun, I moved my 100mm f/6 refractor down to M104 just to see if
I could glimpse the galaxy at all from my driveway in town. I was startled, not
only to easily see the galaxy, but to just barely make out the dark lane! Similarly,
Leo's Trio, and a few galaxies in the Markarian Chain were also fairly easy to catch.
Back in the 9.25 inch SCT, globulars were quite stunning at 196x, with M3, M5, and
M13 being spectacular and nicely framed in that wide high-power field. I even picked
up the “eye” formation of the “Ghost of Jupiter” planetary,
NGC 3242. All in all, I had quite a bit of fun running the 8.5-12mm Speers Waler
through its paces.
There
are some differences between the new version and its predecessor which do need to
be mentioned. The focal length range in terms of a percentage of the longest focal
length is a bit smaller in the 8.5-12mm version than in the original 5-8mm model
(29.2% vs. 37.5% for the original). The 8.5-12mm Speers Waler now has an apparent
field of view that is about 6.5 percent larger than that of the original 5-8mm model, which
was a bit of a surprise. I recently re-measured my 5-8mm version's AFOV at 76.4
degrees, which is notably smaller than its original manufacturer's claim of over
80 degrees, but is still quite good for a shorter focal length eyepiece. Perhaps
the manufacturer wanted to get this new version closer to that original 80+ degree
claim, but even at a 76.4 degree field, the original Speers Waler was definitely
a very good performer with few optical problems. The extra field is nice, but the
8.5-12mm version's attempt at a wider apparent field using only eight elements may
have resulted in some performance issues that were not as much of a factor in the
original 5-8mm model.
The
first thing I noticed when I put the eyepiece into my 9.25 inch SCT was that as
I quickly moved the eyepiece slide out to the shorter focal length and higher power
end of things, the edge of the field seemed to turn ever so slightly darker, as
if the eye cup was starting to intrude into the light from the eye lens. I thought
this might be due to a slight reduction in the eye relief, but tests run indoors
looking into the eyepiece at a white screen showed that what I was really seeing
appeared to be a small amount of field-edge vignetting internal to the eyepiece
itself. This became noticeable mainly for the focal length settings that were less
than 9.5 mm, and it manifested itself as a very diffuse and minor light loss mostly
in the outer 10 percent of the radius of the field of view. I went back to my 5-8mm
model and with some study, detected a similar effect, but it was somewhat lower
in intensity than it was with the new 8.5-12mm model. Perhaps I didn't notice it
originally in the old version because it does not have a hard eye cup to hold the
eye farther out from the eyepiece, or because the apparent field of view of the
old 5-8mm model is slightly less than the new version. A possible reason for this
apparent vignetting may be familiar to those who try to use standard Barlows with
some wide-field eyepiece designs, as the Barlow diverges some of the light enough
to miss the field lens of the eyepiece. Perhaps if Antares had restricted the new
version to the same 76.4 degrees, I would not have noticed this behavior, but the
plain truth is I noted it immediately, although I still consider this to be a minor
problem overall.
Second,
the edge-of-field astigmatism shown in the 8.5-12mm model was somewhat more than
was shown in the original 5-8mm model. At f/5, I would estimate that at the outermost
“ragged-edge” of the field, the astigmatism in the 8.5-12mm model was
close to twice as much as the modest amount that the 5-8mm model presented at its
field edge. The astigmatism seemed slightly less at the shorter focal length settings,
but it was still more than the 5-8mm had shown. This again may be due to the larger
apparent field size, or possibly the fact that the new model has only eight elements
to deal with the light. In any case, it was a bit more noticeable (even in the f/10
of my SCT), and from my standpoint, I might have been happy with just a little less
of that extra wide field of view if it meant better star images. Still, the astigmatism
was mainly a factor only in the very outermost part of the field. It was not nearly
enough to seriously degrade wider-field views of the moon, and star fields were
generally pleasing in the eyepiece, so I still consider the performance of the 8.5-12mm
Speers Waler to be pretty good.
Both
Speers Walers require some inward-focuser travel in order to achieve a proper focus,
and this may present a problem in some telescopes. When used in my 100 mm f/6 refractor,
the 8.5-12mm at the 10mm setting needed about a full inch of inward travel when
compared to the focal position for my 10mm Sirius Plossl. The inward travel needed
by the 5-8mm model seemed to be slightly less than that required for the 8.5-12mm
model, but that may have been due to different comparison eyepieces used to obtain
rough equivalency in focal length. The 8.5-12mm Speers Waler works well in SCT's
and refractors with large focuser travel ranges, but in Newtonians, focuser travel
issues may be present depending on the instrument. I could use the eyepiece in my
friend's 8 inch f/5 Newtonian, but it required a rather special low-profile 1.25”
to 2” adapter to do it. When Barlowed, I also could not bring the 8.5-12mm
model to focus in my refractor when using the Meade model 140 2x Barlow (either
with the Barlow ahead of or behind the star diagonal). This is one reason I am glad
I have the Tele Vue 2.5x Powermate, as that image amplifier almost eliminates the
focus travel problem entirely. Now the times when I might want to Barlow these two
eyepieces are probably rare due to their already fairly short focal lengths, but
it is nice to be aware of potential Barlow problems when considering an eyepiece
purchase.
Summary: 8.5-12mm Speers Waler: Judging eyepiece
performance is a somewhat inexact art, as so much of observer preferences or personal
tolerance of aberration factors in that it can be difficult to give a truly accurate
and unbiased report. Still, overall I would have give this new 8.5-12mm Speers Waler
eyepiece the following letter grades:
Construction: “A-”
(a good solid build, a bit on the heavy side).
Focal Length Range: “B”
(more restricted than with some zoom eyepieces)
Field of View: “A”
(nice wide field wider than many other eyepieces of its focal length range)
Astigmatism Correction: “B”
(might have been better, but was good for the wide field).
Lateral Color Correction: “A”
(better than the 5-8mm version).
Distortion: “B”
(pin-cushion present, but not terribly bad).
Curvature of Field Correction: “A”
(little if any seen).
Contrast/freedom from ghosting: “B+”
(flat back eye lens surface a slight problem)
Eye Relief: “C+”
(does not live up to the “L.E.R.” part
of the WALER acronym).
Overall Optical Performance: “B+”
Cost/Benefit Ratio: “B+”
(worth owning and not outrageously expensive)
Conclusion: the Antares
8.5-12 mm Speers Waler Variable Focal Length eyepiece is a good wide-field eyepiece
for those who need more than one single focal length and wider fields of view at
moderate to higher magnifications.
David Knisely
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