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Borg Refractors: The "80 mm" Family: Part 1: Borg 50 mm F/10 Apochromatic Refractor

(left to right) Borg 50 ED, 76 ED, 100 achromat and 100 ED objectives

Physical Description and Background -- Borg Refractors:

As I found out in researching the Borg products before purchasing my 125 ED, unlike virtually any other telescope, the Borg refractors are completely modular in concept. They are built around three basic 'families' that share some components, 'cross-breed', but are divided into these three families based on the tube diameter. Each family consists of one of more objective lens that will fit on the same diameter main tube. There are multiple tube lengths, focusers (all helical), draw tube, visual and photographic back, and on and on and so forth.

I have provided a more detailed background description of the Borg refractors in my review of the Borg 125 ED available elsewhere at this site. Please see that for any additional information you may need.

The Borg 80 mm Family of Refractors:

The first 'family', which will be covered in this and related reviews, consists of a group of objective cells that all fit on the Borg standard 80 mm diameter tube set, part # 6000. The basic 80mm tube set consists of an 80mm diameter 205mm long optical tube, a draw tube holder and draw tube, the Borg 7835 Helical focuser, a long and a short extension/eyepiece holder, and an adapter. (Remembering that all things Borg are modular, the main tube may be removed and shorter tube (124mm) and slightly modified draw tube substituted for binoviewer use.)

You could simply order this basic unit and then add an objective cell. However, the slightly cheaper way to do this would be to order one of the "telescopes' themselves, and get this basic unit and an objective. In that configuration, you have the equivalent of most other 'telescopes', and need add only an eyepiece and a finder, if desired, and you are ready to go.

And now we start with the smallest of the "telescopes" that Borg sells, the 50 ED.

The Borg 50 ED:

The 80mm family, begins with a package (part # 6050) that adds the 50mm ED doublet objective cell and a lens hood to the basic 80mm set. The current retail price is $418. The result is an f/10 ED doublet that weighs an anorexic 1.5 kg or 3.3 pounds. (The lens cell itself is small and light, weighing only 220g.)

First impression? If I thought the 125 ED was compact and light, the 50ED is astonishing. I received the scope that I had purchased, and the extra objective cells I was reviewing, in their separate shipping boxes. The base unit common to all of this family came already assembled. Taking that out and checking it, it was a smaller version of the OTA for the 125 that I had been using for several months now, the only difference being the length and weight of the unit, and the two set screws that locked down the draw tube. (The 125 (which uses a 115mm diameter main tube) and the 150 ED (which uses a 140mm diameter main tube) rely on the locking knobs of the draw tube itself without the use of set screws.)

The build quality, again, is very good.. The paint on the OTA and the objective cell is smooth and glossy. The finish on the focuser, draw tube, and other parts was very nice, and in distinct contrast to the Chinese refractors that, while priced much less than the Borg, are mechanically very crude and crudely finished in comparison.

I took the base unit apart and checked its components and fit. Again, quite nice. The parts fit together well. The standard tube has a visual baffle shipped pre-installed, a hard plastic, black, knife-edge ring that proved very effective used in conjunction with the other baffle that screws into the front of the focuser. (The focuser baffle is an extra cost, but inexpensive item.) The inside of the main tube is lined with black felt, as is the main tube of the 125 and 150 and all of the other various length tubes I have used or ordered from Borg.

Mating the 50 ED objective (the one to the extreme left, and the smallest objective shown in the picture) takes only a few seconds, screwing it onto the end of the base unit to complete the 'telescope.' The lens hood takes up almost all of the objective as pictured in the lineup below, screwing onto the thin and small lens cell itself, and, unlike the 76 and 100mm objectives -- but like the larger 125 and 150mm units - not a sliding unit but one fixed in place on the end of the objective cell itself. (The 50 is screwed on, the larger 125 and 150 a 'press fit.' Do not grasp the latter by their hoods when mounting.)


Weighing only a skosh over three pounds, and fairly well balanced as the lens cell weighs very little, the 50ED mounts on anything with ease. The picture shows the 50ED mounted on the Borg single-arm AltAz mount (less than a pound) and on the Velbon 640 carbon fiber tripod (less than 3 pounds) using the Borg plastic tube ring (weighing virtually nothing and surprisingly rigid and inexpensive.) I tried the 50 ED on the GP-DX with the SkySensor 2000, and it worked well even though that mount was clearly gross overkill for so light a unit.

The 50 ED will work fine on virtually any tripod and simple mount. The Bogen 410 Geared Head handled this unit with ease, and it is difficult to think of any mounting system that will not work well with this telescope.


Okay, true confession time. I didn't expect to like the 50ED at all when I first received it. After all, what can one do with only 50mm of aperture? A glorified finder? That is what I thought when I read the specifications and when I first assembled the unit. I wanted to test it only to see if I was right.

Well, I was wrong. Dead wrong. The image scale is small, but the detail shown in the scope is as good as what I see through my Takahashi FS-60C. The contrast is excellent, the images crisp and, despite my best efforts, I cannot get even a hint of color out of this scope, in or out of focus!

On the Moon, contrast is very good, and no color off the limb. The scope will take magnification very well, although with only 500mm of focal length and 2 inches of aperture, you find yourself reaching for barlows and Powermates real, and I mean REAL, fast! The detailing on the Moon surface is also excellent, with the small image scale catching up here as the details are crisp, but depicted in such tiny size that ole poops like me have a hard time picking out the details that a younger eye might see easily here. Yes, you can even get craterlets in Plato, but as nice as the detail may be, don't expect to get the detail you will see in a larger scope.

Jupiter is purely a sometimes thing just now, and I was able to get my sights on it only briefly as the Western sky turned dark enough to see it down on the horizon. The details were, again, hard to pick out because of the small image scale, but the low surface contrast was very nice and the banding distinct and not blurred as I had expected. The Jovian moons were tiny but distinct disks, and I even caught a transit at one point in this tiny scope - albeit only long enough to get me to switch to the 100 TMB f/8 on the other side of the Giro -2, which provided a much nicer and larger picture. (Gee, Dave, what a surprise!)

Deep sky was, again, surprisingly good. Unlike many other small aperture scopes, the Borg allows full use of 2" eyepieces, and the star images were nicely resolved tiny (got to stop overusing that word) balls, with the scope coming very nicely into focus.

The 50ED is free of any optical foibles as far as I could tell. Cool down time was virtually non-existent (and advantage no doubt resulting from the small piece of glass that needed to reach equilibrium in the first place) and the scope is one that you can take outside and begin observing immediately in all but the most severe weather.


When Ed Ting tested the Takahashi FC-50, he was impressed with that scope, but also observed that its utility was questionable. The Borg 50ED is in the same category, a small, relatively long (the Tak was an f/8, the Borg an f/10) refractor that is capable of providing sharp, high power images in a lightweight and easy to mount and move package.

However, as crisp as the resulting images in this scope may be, they are still provided in an image scale that limits its planetary and lunar performance, and while its ability as a deep sky performer is no doubt better than the now-discontinued Takahashi FC-50 because of its ability to use 2" eps, it still has to do its job with a minimum of aperture and very little ability to gather light to display for its user. (The FS-60C Tak, on the other hand, is an f/5.9, and uses the more exotic fluorite to offer good correction and the possibility of more than 7 degrees of FOV with a 31 Nagler - of course at quite a high price.)

No, I would suggest that the 50ED is best seen as an introductory scope for someone who wants to buy an ED refractor at a reasonable price ($418) without optical compromise and with a fit and finish that needs no excuses. Given the chance to 'move up' to the larger 76 and 100ED objectives that will fit on the same, 80mm tube set, the 50ED offers the chance to 'see what it is all about' in a better quality refractor before you plunk your money down for that 5" Tak or TMB. Or, if you just like good things in really small packages, or want the ultimate in a 50mm guide scope or finder that can function as a full-fledged telescope, then you have found what you are looking for in the Borg 50ED.


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