Jump to content


- - - - -

Borg 101 Refractor

Discuss this article in our forums
Borg 101ED Refractor

Borg 101ED Refractor
by Lawrence Carlino

When science-fiction aficionados hear the word "Borg," they immediately cringe at the image of the malevolent human-machine hybrids that wreak havoc on the galaxy in Paramount's imaginative and entertaining TV series "Star Trek: the Next Generation."
Fortunately, in the real universe of astronomy and telescopes, the word is simply a contraction of two Japanese terms for "telescope equipment" ? no collective consciousness or evil intent implied or suggested.

With a host of modern apochromatic refractors to choose from, particularly in the popular 4-inch aperture, finding the one ideal for a given observer's needs is both a joy and a challenge. If light weight and portability are not a primary concern, fine instruments in this range are available from Astro-Physics, Takahashi, TeleVue, Stellarvue, TMB, Vixen, and several others. But for those who require 4" APO performance in a svelte airline-portable package, the choices shrink markedly. Try for a tube length of less than 22 inches coupled with a weight of under 6 pounds, and only one possibility remains: the Borg 101ED.

Made in Japan, Borg refractors are uniquely modular in construction. They are offered in "packages" as a complete OTA or as a plethora of individual components that can be tailored to specific needs and preferences. Currently, the 101ED is Borg's largest offering, and it can be configured as a visual or photographic/ccd instrument. Two different tube diameters, 80mm and 115mm, are available, and the myriad available accessories provide a host of visual and photographic iterations. A dedicated ccd reducer/corrector transforms the Borg into an f/2.8 instrument, and an f/4 photo version is sold as a complete OTA. Complicated as this might appear, the good people at Hutech, Borg's US distributor, provide an excellent level of customer support in explaining and selecting the best configuration for an individual's needs.

As I am primarily a visual observer, the Borg 101ED visual OTA seemed the best choice. Using the 80mm tube set and a Borg helical focuser, this 4-incher has a focal length of 640mm and an f/ratio of 6.3. It is remarkably small and light, having an overall (dewcap-retracted) length of 20 inches and a weight of less than 6 pounds. Further, the objective lens assembly can be unthreaded from the main tube and the focuser drawtube removed. The resultant components easily fit into a very small carrying case ? a natural for air travel. For those who can get by with less aperture, both the Borg 77mm ED and 77mm achromat are interchangeable with the 101ED objective lens assembly.

Finished in glossy white with black accents, the 101ED creates an impression of quality workmanship. There are no plastic parts save for the snap-in dustcap. Everything else is made of aluminum or glass. At its current price of $1730, the scope is not exactly inexpensive, but it does undersell most of the competition. Add the white-finished Borg tube rings for the 80mm diameter main tube and a 6x30 finder, and the price escalates another $160. Other worthwhile options include the larger 9x50 finder, the more robust MDX helical focuser for heavy loads, and the wonderful Starlight Instruments dual-speed Feathertouch focuser that can be ordered with the original OTA or as a retro-fit.

Borg advertises the 101ED as an "apochromat," but that appellation hangs on one's personal definition. For the purist, a short-focus, 2-element ED lens, no matter how well made, can't defy the laws of optical physics and be perfectly color corrected. But it can be very good. Is the Borg ED completely free of spurious color? No. But is its color correction far superior to that of an achromat? Absolutely.

Putting the Borg to a variety of observational tests, I discovered several things immediately: First and foremost, the objective lens was significantly miscollimated, probably due to jostling during the long trip from Japan or from temperature changes. This is the third 4-inch Borg I've owned {a 100ED and 2 101ED's}, and all three arrived out of proper alignment. Fortunately, detailed instructions are provided for re-collimation, and the procedure can be accomplished by the user with reasonable ease. Removing the sliding dewcap reveals 4 recessed hex-head screws at 90 degree intervals in the lens cell. By using the tiny (and I DO mean TINY) hex wrenches provided, in a push-pull arrangement, the user re-centers the rear ED element. This requires some patience and finesse, but the eventual result is dead-on optical alignment. Care must be taken to avoid excessive tightness, as pinched optics could result, particularly in cold weather.

Secondly, the light weight and small overall size of the scope made it a snap to support it on a variety of mounts, some of them normally suitable for only 3-inch or smaller instruments. A Universal Astronomics Unistar Light alt-azimuth supports the scope with reasonable stability and a three-second damping time. A Celestron CG-5 equatorial verges on overkill, as damping is nearly instantaneous. Although I don't have one, I imagine that a sturdy photo tripod and head would provide adequate support. Regardless of the mount employed, it's obvious that the Borg is the king of grab-and-go in the 4-inch refractor category.

Portability notwithstanding, it's usually optical performance that determines a telescope's true worth. For testing the Borg, I was fortunate to have several "benchmark" refractors available for direct comparison: a very fine Takahashi FS-102 fluorite doublet; a Vixen 114mm, f/5.3 ED; a Vixen 80mm, f/8 fluorite; and a Celestron/Vixen 102mm, f/9.8 achromat. A friend's Astro-Physics 105mm Traveler was also made available. Over more than a dozen evening observing sessions and a couple of forays into the frigid pre-sunrise morning air, I was able to get a solid impression of the Borg's optical quality.

And that quality is good, but not up to the lofty standards set by the Takahashi and AP refractors. Star testing of the Borg revealed a fairly well corrected optical system with just a hint of astigmatism and spherochromatism. Inter and extrafocal stellar patterns displayed the characteristic blue and cyan coloration that switched position on each side of focus ? typical in an ED doublet lens, and the fresnel rings themselves were relatively concentric and clean. Certainly not bad, but short of the textbook perfection displayed by the Takahashi.

With the first quarter moon presenting an attractive target, I inserted high-quality TeleVue and Stellarvue dielectric star diagonals into the scopes' drawtubes and went to work. With a TV 7mm Nagler Type 6 generating 91x, the Borg displayed sharp, high-contrast views of the lunar surface. The Altai Scarp and heavily cratered lunar south stood out in bold detail despite mediocre seeing conditions. There was no trace of the violet fringing generated by achromats, and the area north of Eudoxus and Aristoteles gave an "I'm in orbit" impression where the telescope's optics seemed to disappear. Several nights later, with the power boosted to 183x (3.5mm Nagler Type 6), the delicate Rima Birt near the Straight Wall was clearly visible, and the chain of tiny craterlets close to Copernicus showed easily in moments of steady seeing. As impressive as these views were, they lacked the stark contrast and color purity of the Takahashi FS-102. The Tak had a more satisfying "snap" to focus, and the Borg had a tendency to show black shadows with a deep red fringe if even the slightest bit out of focus ? something that occurred regularly as atmospheric turbulence came and went. With a Takahashi 2.8mm LE eyepiece (229x) this trait became an annoyance. However, the Borg generated none of the purple"wash" that severely compromised the Celestron/Vixen achromat at similar powers. The 80mm Vixen fluorite provided a sharper and more pleasing image than the 101ED or the achromat, though the image was not as bright.

With Mars looming in the eastern sky, its disk size close to 20 arc-seconds, all of the refractors gave impressive, detailed images of the Red Planet. At 128x, using a 5mm Orion Ultrascopic eyepiece, the Borg clearly presented the pale pinkish-orange disk, a prominent Syrtis Major, Mare Serpentis, a bright Hellas region, the north polar hood, and several limb brightenings. A tiny splash of excess red that came and vanished with variations in seeing conditions surrounded the planet. Overall, contrast was quite good, and a #21 orange filter further improved the view and allowed powers to be boosted to the 230x range without significant image breakdown. Again, however, the Tak FS-102 was superior. Though it showed no more detail than the Borg, that which was visible was easier to discern, and it remained more easily visible when the seeing degraded. The Vixen 114ED, despite its short f/5.3 focal ratio, also outperformed the Borg in image contrast, but it embedded the planet in a faint violet haze that was absent in the 101ED.

Perhaps the main factor here is the new "eco glass" that Borg employs in the lens' ED element. Superseding the older fluoro-phosphate glass used in the Borg 100ED, this "environmentally friendly," lead-free material seems to have different optical characteristics, perhaps better suited to photographic and ccd applications than the visual. The Borg 100ED that I owned several years ago strikes me as having been a slightly better instrument for visual use. Another factor may be my own abnormally high sensitivity to red light ? great when detecting the rosy extensions of the Great Orion Nebula and the outer shells of bright planetary nebulae, but not so good on point sources. It's quite possible that observers with normal color perception would find the Borg's red excess minimal or invisible. For the record, I have found a similar color "error" in the Orion 80ED and William Optics Megrez 80 ED triplet. Just call me "H-Alpha eyes!"

With Jupiter caught in the pre-sunrise turbulence, I turned to the late-rising Saturn. As expected, the ringed planet provided an impressive sight in all of the telescopes in spite of rather unsteady seeing conditions. At 91x, the Borg easily revealed the Cassini Division in the rings and the planet's South Equatorial belt. Stepping up the magnification to 128x with a 5mm Orion Ultrascopic brought out the dusky south polar area, the crepe ring where it crossed the planet's disk, and four moons. Contrast and rendition of the delicate Saturnian colors was quite good, but the image again fell behind that of the Tak FS-102 and Vixen 114ED. These scopes seemed less affected by atmospheric turbulence, had sharper definition, and generated images that were simply more impressive to the eye.

Double stars, frequently an effective test of a telescope's optics, were targeted next to further evaluate the Borg. Epsilon Lyrae, a classic favorite, was beautifully and cleanly resolved with the 101ED operating at only 67x with a 9mm Nagler type 6. At 128x, using a 5mm Type 6, the hard, sharp airy disks of the stellar quartet were surrounded by delicate first diffraction rings tinged with just a hint of reddish coloration. Tweaking the focus would eliminate the red, but the airy disks were rendered a bit less distinct. Both the Tak FS-102 and Vixen 80mm fluorite showed dead accurate color fidelity at similar magnification.

Zeta Aquarii, a much more challenging test, was clearly resolved with the Borg at 168x using an Orion 3.8mm Lanthanum eyepiece, as was the close, difficult companion to Delta Cygni. The smooth, progressive motion of the scope's calibrated helical focuser made obtaining a tightly focused image easy to achieve, though the twisting motion required generates a bit more vibration than does a conventional rack-and-pinion or Crayford unit. The Borg focuser showed no tendency to bind under moderate loads, but with a heavy 2-inch diagonal or binoviewer attached, one might consider the heavy-duty MDX helical or Feathertouch options.

A host of other "test" double stars gave the Borg little or no difficulty. Castor's close pair of suns resolved at 128x with no intervening haze or sloppiness, and the companion to Rigel was easily separated from the glare of its brilliant primary at powers as low as 67x. Quite pleasing overall. Yet, the relatively easy Alpha Herculis displayed some red excess around its ruddy primary star, especially in moments of atmospheric turbulence ? a trait not displayed by the two Vixens or the Takahashi.

While no 4-inch telescope can be regarded as a deep-sky dynamo, the Borg acquits itself quite well. The hard, sharp stellar points generated at all powers and effective suppression of glare create better-than-expected magnitude penetration and contrast. The multi-coated objective lens and thorough tube baffling do their job effectively and enable some very satisfying views.

With light grasp nearly identical to that of the Tak FS-102, the Borg resolved M 13 to the core at magnifications of 91 and 128x, the Nagler Type 6 eyepieces providing a wide and impressive framing window. Here, the Borg outperformed the smaller 80mm Vixen by a significant margin, and it also had a slight edge over the Celestron/Vixen achromat. Only the 114mm Vixen gave a better view, largely as a function of its greater aperture. With a TV Everbright 2-inch star diagonal and 40mm Orion Optiluxe eyepiece attached, the Borg also served admirably as a rich-field telescope. At just 16x, with a field-of-view of nearly 4 degrees, the Borg provided a marvelous starscape of the Milky Way near Deneb and an impressive wide-angle sweep through the rich Sagittarius region. The Andromeda Galaxy strikingly revealed its faint extensions, both satellite galaxies, and hints of dark lanes. With the magnification boosted to 49x using a 13mm Nagler Type6, the Double Cluster in Perseus provided dozens of gleaming stellar pinpoints against a velvet background. A lovely sight, but one that fell just a bit short of the intensely BURNING stars served up by the Takahashi FS-102 at the same power. The difference was subtle but unmistakable.

So where does the Borg 101ED stand in relation to its peers? Clearly, it is a good telescope that is less expensive than most of the competition. Its color correction is far better than that of an achromat, but it trades the characteristic excess violet (at least for my eyes) for too much red. It does create some very pleasing views of the moon, planets, multiple stars, and deep sky objects ? yet it falls noticeably short of the textbook optical quality revealed by the Takahashi FS-102, AP Traveler, Vixen fluorite, and probably most other ultra-high-end APO refractors. True perfectionists might find it mildly disappointing, but the majority of observers and photo/ccd imagers would probably find the Borg to be very satisfactory. With a three-year warranty and excellent customer support from Hutech Corporation, the 101ED is a safe and affordable bet.

The Borg's true ace card is its small size, feather weight, and incredible portability.
Nothing else matches this particular combination of virtues. With that in mind, it's the clear winner for the frequent traveler or observer with limited storage space.

And one other thing: Unlike its "Star Trek" namesake, my Borg doesn't communicate with other Borg(s) using sub-space signals (at least as far as I can determine), nor does it have any aspirations of galactic conquest.

Clear and steady skies!
Larry Carlino

p.s. I have no affiliation with Borg or the Hutech Corporation, nor have I ever been a member of the Borg Collective or received implants of Borg components.

  • Ephemeral likes this


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics