The
Simpler…The Better
By
Phil Harrington
It
is often said that simplicity breeds purity. When considering telescopes, this
axiom holds true, especially with the Tele Vue 102
and its imaging capabilities.
Ever
since company founder Al Nagler introduced his
line of Plössl eyepieces in 1979, Tele Vue
has set the standard in quality optical products for amateur astronomers. In
1982, Nagler decided to enter the high-end
refractor market with his MPT (Multi-Purpose
Telescope). This was followed by a number of different instruments, including
the Renaissance, Genesis, Pronto, Ranger, Tele Vue
85, Tele Vue 101, and the limited edition Tele Vue
140.
Most
recently, Tele Vue introduced a refractor called
the Tele Vue 102 (TV102).
The heart of this telescope beats around a 4-inch f/8.6 objective lens. Unlike
the TV101, which focuses starlight into the
eyepiece using a complex of four separate lens elements set in two groups, the
TV102 has a simpler two-element design.
The
optical interplay of these elements produces tack-sharp images of the moon,
planets, stars, and brighter deep-sky objects, which are nearly devoid of the
false color (called secondary spectrum) that plagues many achromatic
refractors. I have been fortunate enough to use several TV102s
since the telescope was first introduced in 2000, and all have performed
flawlessly.
As
is custom with every telescope I evaluate, I began by performing the “star
test” — the tell-all check that compares the appearance of a star slightly
inside of focus versus slightly outside of focus. Each TV102
displayed a perfect set of diffraction rings on either side of focus, just as
a high-quality telescope should. And for those who are interested, I would
estimate the final wavefront at the eyepiece to be
no less than 1/8 wave, or even better. If you’re not familiar with such
optical jargon, then this is just another way of saying the optics in the TV102
are among the finest in this telescope’s size and class.
Let’s
put some of this perfection into practice. When viewing the moon through an
achromatic telescope, the lunar limb is usually accentuated by tinges of blue,
purple, or yellow, depending on how you hold your head to the eyepiece. These
telescopes also show similar false colors, or secondary spectrum, around
brighter stars and planets (unless the telescopes’ focal ratios are quite
high, greater than about f/13 for a 4-inch scope). However, an apochromatic
refractor should eliminate secondary spectrum entirely. Even at high power,
the TV102 gave only the slightest hint of
secondary spectrum around Vega, and absolutely none when viewing the moon.
Speaking
of the moon, I could spend hours exploring the countless nooks and crannies on
the lunar surface visible through the TV102. And
while the level of detail was exquisite, what really impressed me was the
lunar starkness. Unlike some traditional achromatic refractors, which seem to
cover the moon with a haze due to scattered light within the instruments’
optical systems, the TV102 displayed detail with
amazing definition. The shadows that covered the crater floors near the lunar
terminator were pitch black, rather than a milky gray, while crater rims, rilles,
and mountain ranges all showed a crispness.
Turning
to more traditional deep-sky objects, my first target was Epsilon Lyrae,
the famous Double-Double star. With a 9mm eyepiece
(97x) in place, all four components were easily and
cleanly resolved. Next stop was M13, the Hercules Cluster. Using a 12mm
Tele Vue Nagler
eyepiece (73x), the cluster dissolved into countless stars, with many strung
together in arcing threads, giving the appearance of legs reaching out from a
giant celestial spider. Several other globular clusters, including M2, M10,
M12, and M92, were also well defined with the TV102.
Perhaps
my favorite views came when I paired the TV102
with my 22mm Tele Vue
Panoptic eyepiece. This combination yielded a magnification of 40x and an
impressive 1.7o field of view.
Favorites such as the Lagoon Nebula (M8) and the Double Cluster (NGC 869 and
NGC 884) quickly became sparkling gems against their brilliant, star-filled
backdrops. Incidentally, a 55mm Plössl
will produce the TV102’s largest field of view:
three degrees.
Light
throughput is excellent with the TV102, as
evidenced by glimpses of stars up to 13th magnitude — not bad for a
“small” telescope. Image contrast is also superlative with the TV102,
with fine details in the many belts of Jupiter showing through clearly. The
more subtle features of Saturn’s atmosphere were also evident, as was Cassini’s
Division in the planet’s rings. The Crepe, or C
ring of Saturn was also apparent, silhouetted against the bright, yellowish
planetary disk.
Photographically,
the TV102 should be a winner, although I did not
test it in this capacity. Tele Vue cautions that a
field flattener is needed for distortion-free photography of star fields. A
dedicated 0.8x reducer/flattener is available that reduces the TV102’s
focal ratio to f/6.9, while also producing pinpoint star images from edge to
edge.
The
TV102 performs just as well mechanically as
optically. Although the tube assembly weighs only 10 pounds and measures 31
inches from tip to tip, it feels quite sturdy. The 2" focuser, made from
machined aluminum with internal Teflon pads, glides in and out with just the
right amount of effort (although it can be adjusted, if desired) and shows no
evidence of wobble or backlash.
Unlike
other Tele Vue telescopes, the TV102
is sold without an eyepiece, star diagonal, or tripod-mounting ring. If you
are a first-time refractor buyer, then you also have to select and purchase
those items, as well as a suitable mounting. Although this may seem like a
drawback, it actually allows the purchaser to customize his or her accessories
to suit individual needs. Unless you already own one, you will need to buy a
2" star diagonal, such as Tele Vue’s own Everbrite
diagonal; several other manufacturers also offer suitable units, which
typically range in price from $100 to $255. Unless you plan on using only
2" eyepieces, be sure to get a 1.25" adapter, if one is not supplied
with the diagonal.
A
finder may also be on your shopping list. Select from a one-power “unity”
finder, such as Tele Vue’s Starbeam
or Quik-Point, or a magnifying finderscope
— all priced between $25 and $180.
Finally,
you may need Tele Vue’s ring mount (Item # RM4-0001,
$120), which mates the TV102 to any tripod with a
standard 1/4-20 photographic mount. The Tele Vue
Gibraltar altazimuth mount is ideal for the TV102,
as are the Vixen Great Polaris or GP-DX, Celestron
CG-5, and Losmandy GM-8 equatorial mounts.
The
Tele Vue 102 has quickly established itself as one
of the finest refractors in its size class sold today.
Phil
Harrington’s equipment reviews appear often in Astronomy. His book Star Ware
is available through bookstores as well as his website: http//www.philharrington.net.
Reproduced
by permission. Copyright 2001 ASTRONOMY magazine, Kalmbach Publishing Company.