These impressive binoculars
provide brilliant, wide-field views of celestial objects.
BY PHIL HARRINGTON
JMI's RB-66 binocsope
Mention binoculars, and most of us envision a
pair of small prismatic refracting telescopes joined together by a central
spine. Their small size and light weight make binoculars perfect for an
impromptu viewing session — whether a distant scene, a bird in flight, or a
look at the night sky. Of course, not all binoculars are small and
light. Some are large and heavy. Despite their differences in size,
however, all binoculars have the same basic design. Until now.
A new concept
Late in 2002, Jim's Mobile, Inc. (JMI) introduced an innovative product
called the RB-66 binoscope. The "RB" stands for "Reverse
Binoculars" something the amateur market hadn't seen. The RB-66 is,
in effect, two 6-inch f/5 Newtonian reflectors with a protective
"clamshell" of molded plastic surrounding the entire assembly.
The RB-66 comes with an alt-azimuth mount that attaches
to a Celestron tripod. Accessories include two 20mm matched Plössl
eyepieces (any two identical eyepieces will work), two Celestron 1¼"
mirror star diagonals, and Celestron's Star Pointer red dot unity finder.
JMI's own NGC-microMAX digital setting circles (with a database of 245 objects)
is an optional accessory. The mount is predrilled to accept the NGC-microMAX
and its encoders. A highly recommended accessory is a foam-lined, wheeled
carrying case. The case helps when the RB-66 must be moved or shipped.
Light enters the two tubes of the RB-66, reflects from the primary to the
secondary mirrors, and exits through focusers that face each other. A pair
of star diagonals then turns the light path 90°, toward the front of the
instrument where the observer views from a seated position. The tubes are
separated by about 10 inches, so the observer's head won't block the view.
One problem JMI overcame was how to focus the
image. Conventional focusers move in and out, but that would never do for
the RB-66 because the distance between eyepieces (called the interocular
distance) changes every time they're focused. This distance has to be
adjustable for each observer, but once set, it needs to remain fixed.
To solve the dilemma, JMI modified and motorized their
RCF-mini1 focuser to slide parallel to the tubes. Each secondary mirror
holder is permanently attached to the focuser to move with the eyepiece.
The focusers are independently adjusted by pushing two sets of buttons on the
RB-66's control panel, which is located between the tubes.
Interocular distance also is adjusted electrically with
a rocker switch. The controls' motions are smooth, although focuser
travel is a little fast. I would have preferred a two-speed control to
make critical focusing easier. The folding control panel also has a pair
of foam-covered, motorcycle-style handles for pointing the binoculars.
A 6-volt, 4.5-amp-hour rechargeable battery hidden inside the pier supplies
power for the RB-66's motorized focusers and adjustment motors. Just
insert the plug into the connector mounted on the pier, and the system is ready
to go. A charger that comes with the telescope plugs into a standard wall
socket to recharge the battery when needed. This battery really holds a
charge. Although I used the telescope extensively for more than a month, I
never had to recharge the battery.
The RB-66 arrived from the factory in two boxes, one holding the binocular
telescope in its molded carrying case, and a second containing the tripod.
The RB-66 comes from the factory fully assembled. Just remove a shipping
brace and attach the finder to the protective cover.
To se up the RB-66, first open the tripod and adjust
the length of its legs. At this point, attach the tripod's leg spreader to
strengthen the assembly. Before lifting the binocular unit out of its case
and onto the tripod, tighten the vertical position lock to hold the binoculars
rigidly to the alt-azimuth mounting. This way, the mount won't flop around
when the instrument is lifted by the top-mounted handle. Place the
mounting base on top of the tripod and bolt the two together using the three
Although this sounds simple, it takes some getting used
to. I had difficulty positioning the instrument's base exactly over the
tripod's three mating holes, especially at night. An alignment pin or some
other reference key machined into the base of the RB-66 would have made the
whole process much easier.
Once the telescope and tripod are bolted together, they
can be carried as a unit to your favorite viewing spot by lifting the carrying
handle with one hand and the base with the other. But be forewarned:
The RB-66 is no lightweight. The inseparable binocular telescope and
alt-azimuth mount weigh nearly fifty pounds, and the tripod adds another
ten. Because of its weight and ungainly shape, the assembled system may be
difficult for some observers to move alone.
Like using any reflecting telescope with a fast focal ratio, the first thing
to do when setting up for an observing session is to check the system's optical
collimation. The test instrument arrived with both sides out of
collimation, but gaining access to the three adjustment screws behind each
mirror was easy: I simply removed the instrument's carrying handle and
pulled away the cover's top half.
Once collimation is complete, both telescopes must be
aimed parallel to one another, an easily accomplished task. Aim the RB-66
at a known object such as the Moon or a bright star to check and adjust
this. Center the target in one of the eyepieces and then look through both
eyepieces. By flipping the two rocker switches back and forth on the
control panel, a pair of electric motors moves the telescope on the observer's
right horizontally and the telescope on the left vertically. As the
instructions advise, move the horizontal adjustment first, until the two images
of the target lie directly above and below each other. Then, use the
vertical motor to merge the two into one. If the process is reversed and
the target is aligned horizontally first, the observer's eyes will try to merge
the images by crossing. "Crossed eyes" frequently cause eye
fatigue and headaches when an observer is using misaligned binoculars,
regardless of their size.
The alignment process gets even easier with practice,
but I would have preferred the alignment motors to have both low- and high-speed
settings, because I often overshot the exact point where the images
merged. It's also easy to confuse the two identical switches that control
the alignment motions, since both rock left to right. A better design
would have been for the left-hand (vertical) switch to be mounted perpendicular
to the other. That way, both switches would toggle in the direction they
move the telescopes.
Time to observe
As luck would have it, the sky was clear to first night after I received the
RB-66, so I eagerly walked it outside and set it up for a look around. I
didn't bother waiting for complete darkness before aiming at my first target,
the waxing crescent Moon. My first impression?
"Wow!" The sunlit part of the lunar surface was sharp with
excellent contrast, but the portion lit only by earthshine really impressed
me. Binoculars seem to show that area better than telescopes anyway, but
the RB-66 outdid any I have used. The view of the still-dark maria and
major craters along with the illuminated crescent created a surreal, faux 3-D
effect that was quite striking.
After twilight faded, I turned the instrument toward
Jupiter. The supplied 20mm eyepieces produce only 38x — not enough to
see great detail but enough to show all four Galilean moons, the planet's north
and south equatorial belts, and many other features.
Wile there may be telescopes better suited for
planetary observing, the RB-66 is in a league of its own when it comes to large
deep-sky objects like the Orion Nebula (M42), the Lagoon Nebula (M8), and the
Andromeda Galaxy (M31). I was particularly impressed with the RB-66's view
of open star clusters. The Double Cluster in Perseus (NGC 869 and NGC
884), for instance, really sparkled across the RB-66's 1.3° field of view.
I also was struck by how much image contrast improved
when using both eyes. Whether it was the faint, luminous bridge connecting
the Whirlpool Galaxy (M51) to its irregular galactic neighbor NGC 5198, or the
gentle rifts of the Lagoon Nebula, object contrast and brightness where enhanced
when I used both eyes as compared to viewing through just one side of the
binoscope. There was also a slight improvement in limiting magnitude (the
faintest stars that can be seen), typically between 0.1 and 0.2 magnitude.
Optics and mechanics
To star-test the RB-66, I checked each optical assembly using a 10mm Tele
Vue Radian eyepiece and 2.5x Powermate, which produced 193x. Both
telescopes had excellent optics that produced textbook diffraction patterns,
giving little indication of optical aberrations. It's critical for a
binocular telescope to have identical sets of optics because even a slight
difference in focal length between the two will create viewing problems.
As far as my visual tests could determine, both 6-inch telescopes were equal in
Few binoculars can compare to the RB-66. The best known, comparable
system in the 6-inch size range is the Fujinon 25x150 MT-SX binoculars, which
retails for about $6,000 (mounting extra). The higher cost and fixed
eyepieces of the fujinon binoculars are distinct disadvantages, but setup time
is reduced — there's no need to collimate optics or align tube assemblies.
If you're looking for breathtaking low- and
medium-power views of star fields, nebulae, star cluster, and the Moon, give the
RB-66 from JMI serious consideration. For observers who appreciate the
wonderful views seen only through a true binocular telescope, the RB-66 is a
Optical system: 6-inch f/5 primary mirrors, 1.6-inch secondary
Interocular spacing: Variable from 2 inches to 3.25 inches
Weight: 49.4 pounds
Height: 29.5" (locked into vertical position)
Depth: 10.5" (folded)
Tripod weight: 9.6 pounds
· Two 20mm matched Plössl eyepieces
· Two Celestron 1¼" mirror star
· Celestron Star Pointer red-dot unity
· Protective white clamshell cover
(available in black by special order)
· Six motors for adjusting interocular
spacing, focusing, and optical tube alignment
· Rechargeable battery and charger
· NGC-microMAX computer, $399
· Carrying case with wheels and handles,
Jim's Mobile, Inc.
8550 W 14th Ave, Ste 200
Lakewood, CO 80215
[t] 303.233.5353; 800.247.0304
Phil Harrington is the
author of the new observing guidebook Star Watch.