Pocket
Borg Review
The
Pocket Borg is the lightest, most compact way to enjoy the Moon.
Doubtless
quoting yourself is the first sign of madness or megalomania, but here goes.
When I reviewed the MiniBorg a few years ago I wrote ‘if a smaller, lighter,
more compact astronomical telescope exists, then I don’t know about it’. Since
then Borg have introduced two smaller scopes to confound me. So I thought I’d
try the smallest of them all – the 25mm Pocket Borg. Famous last words,
but this really is the smallest astronomical telescope you will ever be
able to buy.
Stop
laughing. I know what you’re thinking. What possible use is a 25mm scope? This
thing has the same focal length as the aperture on my TMB 175;
half the aperture of its finder!
But
if you’re thinking the Pocket Borg is useless, let me challenge you with two
questions:
When
you go on holiday or travel for business, how often do you take a scope with
you?
How
often have you found yourself on one of said trips, looking at something in the
distance and thinking ‘wish I had a little scope with me’?
For
me the honest answer to those questions would (still, having owned many
supposed travel scopes) be ‘never’ and ‘regularly’.
If
you’re much the same, then the Pocket Borg might just be for you. It’s so small
that you could take it with you without thinking about it much, wherever you
go. And when you get there, a one inch scope might be more useful than you
think.
At
A Glance
|
Telescope |
Pocket Borg |
|
Aperture |
25mm / I” |
|
Focal Length |
175mm |
|
Focal Ratio |
F7 |
|
Type |
Achromatic refractor |
|
Length |
~12cm Astro’ / 17cm monocular (incl visual back) |
|
Weight |
~175g (depending on visual back used) |
Data
from Me.
Design
and Build
Despite
its tiny size, the Pocket Borg is engineered in true Borg fashion to match
their larger kit – beautifully finished, light in weight … and with lots of
threads! This is really where the Pocket Borg adds value. Borgs are well-known
for their flexibility and the Pocket Borg is like their larger models in this
respect. A tiny scope it may be, but Borg seem to have worked hard to make it
as adaptable to different roles and configurations as possible. You could
easily use it in any of the following ways:
1) A miniature
astro’ scope with a diagonal and 1.25” eyepiece that mounts on a small photo
tripod.
2) A
straight-through spotter on a photo tripod.
3) A highly
configurable 25mm finder, either right angle or straight-through, with an
illuminated reticle eyepiece if you want.
4) A tiny
hand-held monocular.
5) A
miniature telephoto lens: natively 175mm F7, or pair it with a 2.5x TeleVue
Powermate to create a, sharp 438mm F18 lens. Push things with a 5x Powermate
and it still works at 837mm, but is very dim at F36, so you will need a tripod
and high ISO.
Optics
Pocket
Borg Objective.
One
good thing (and we need to find a few) about a 25mm scope is that chromatic
aberration is no longer an issue. It’s an achromat by design, but optical
theory suggests the Pocket Borg should be almost APO-like at F7. So if the lens
has been well-ground and polished, near-perfection is possible (and with so
little aperture we’ll need it to see anything).
On
the face of it, all we can say about the Pocket Borg’s objective is that it’s a
tiny well-coated achromat in a threaded cell that’s integral with the
dew-shield. It does look better and rather different to the objective on your
average small finder: just like a MiniBorg objective unit, in fact, only
much smaller!
One
advantage of such a tiny focal length is the enormous field of view on offer.
With a 1.25” eyepiece, the Pocket Borg has a maximum true field of almost 9°,
wider than almost any binoculars.
Ridiculous?
With a Pocket Borg and Ethos 13mm you get 13.5x magnification and 7.3° FOV!
Tube
Pocket
Borg Components: Focuser, extension and objective.
Pocket
Borg configured as a 12x monocular.
Pocket
Borg configured as an illuminated finder.
Pocket
Borg as a 175mm telephoto.
As
you can see, there are lots of ways to configure the Pocket Borg. Let’s look at
how Borg have built-in this flexibility.
The
white-painted part of the tube has an integral threaded extension section. This
is because the Pocket Borg can be used straight through as a monocular, or as a
DSLR lens (insert extension) or with a diagonal (remove extension). The photo
on the Hutech (Borg’s US reseller) website shows the Pocket Borg on a tripod
with the extension in place and a diagonal in the back: it’s wrong.
The
rear section of the OTA – the satin black part – bells out to end in a in an
M36.4 metric thread that accepts various 1.25” visual backs. The standard Borg
visual back (part 7317) is one option, but has locking screws and will mar your
diagonal barrel; I threaded-in a Takahashi unit which has a twist grip.
Finally,
the OTA is properly designed to counter stray-light: there is a knife-edge
baffle in the focuser tube and the inside of the OTA and focuser unit is ridged
with machined-in micro-baffles.
Pocket
Borg extension tube has machined-in micro-baffles to prevent stray light.
Borg’s
smallest helical focuser should thread or slot in for finer focus control.
Focuser
The
Pocket Borg focuses by simply sliding the white tube over the black rear section.
It sounds crude, but in practice it’s easy to get focus at any power
the Pocket Borg will cope with. For photography, it could do with a small
helical focuser and Borg make one that should thread straight on … for a price.
Mounting
That
black rear OTA section incorporates a ¼-20 thread for a photo tripod which is
handy: unlike the MiniBorg the thread is integral so there is no mounting block
to get in the way if you want to use it as a finder or monocular.
Pocket
Borg has ¼-20 thread built in.
It
goes without saying that the lightest photo tripod is more than enough for the
Pocket Borg. As shown above, mounted on a table-top mini tripod with a
ball-head, it really is a complete system you could put in a pocket.
In
Use – Daytime
At
low powers with a decent Plossl the Pocket Borg gives good daytime views. In
fact, the view with a 25mm TeleVue Plossl at 7x is really excellent. It reminds
you of how much erecting prisms take away, so absolutely sharp is the view and
still plenty bright enough, even in dull weather. And just as we thought, the
small aperture and longish focal length mean no apparent chromatic aberration.
Enlargement
of daytime branches (albeit against a very dull sky) shows minimal chromatic
aberration.
Getting
the Pocket Borg to yield high powers is a problem. Theory suggests even a
one-inch scope should cope with 30-50x magnification, but with only 175mm focal
length that means eyepieces of 3-6mm focal length. Now that’s fine if you have
£300 worth of Nagler Zoom to hand. But it’s a problem if not, because the
Borg’s short focal length doesn’t work so well for conventional eyepieces -
like Plossls and Orthos - below about 7mm F.L.; they seem to end up with almost
no eye relief. The Pocket Borg works much better with eyepieces that have a
built in barlow lens to increase the effective focal length of the objective.
Attaching
such exotic eyepieces to a small cheap scope seems and looks odd, but works.
Daytime views at 35x with a 5mm Nagler Type 6 (an eyepiece that costs three
times as much as the scope) are close to ideal for terrestrial use
in bright conditions, but not at dusk or when it’s very dull. The view
remained bright and sharp, with just a trace of chromatic aberration creeping
in out of focus.
The
Pocket Borg makes a very lightweight 175mm F7 terrestrial telephoto lens too –
just add a suitable T-mount. You can see a terrestrial snap taken with it below.
Ahhh, but 200mm lenses are cheap as the proverbial these days. Well indeed, but
the Pocket Borg is a telescope so it’s optic is sharper on-axis than
a typical camera lens. Off axis a camera lens is better corrected of course.
Daytime
shot through Pocket Borg as a 175mm telephoto lens: very sharp on-axis, but
quite curved at the edges.
In
Use – The Night Sky
Star
Test
With
so little aperture perfect optics are essential and fortunately the Pocket Borg
has them. The star test is virtually identical either side of focus
with nice evenly illuminated rings and perfect collimation.
Moon
With
such a small aperture even the full Moon isn’t blindingly bright, even at low
powers – a real advantage if you enjoy looking at the full Moon’s brilliant ray
system.
At
higher powers, the Pocket Borg gives good views of the Moon at 50x with a 3.5mm
Nagler T6: perfectly sharp and with minimal in-focus chromatic aberration. On a
gibbous Moon in twilight, I was able to watch sunrise highlighting just the
rims of the crater arc within Clavius, whilst the rest of crater remained in
darkness; ditto the central peak in Tycho. I could easily make out the dark
patches in Alphonsus and just resolve the Great wall. Mons Piton and Pico stood
out clear and bright from the Mare.
On
another night, I was quite surprised to find that a 2.5mm T6 Nagler giving 70x
also worked well on a Moon just past full. Two highlights were the mountains
around the rim of Mare Criseum and the Messier twin craters with their double
ray. The bright limb was surrounded by a dark purple halo, but this did nothing
to spoil the view or the contrast.
This
is a situation where the Pocket Borg refutes the idea that a one-inch scope is
useless: no hand-held binoculars will show you that level of Lunar detail. Put
it another way: the Pocket Borg would outperform anything available to Galileo
or his contemporaries.
Planets
Unlike
binoculars or terrestrial spotters - encumbered with prisms that cause flare on
small bright objects - the Pocket Borg does well on planets for its aperture.
At
30-50x it will just about show you Jupiter’s equatorial belts and polar hoods
and Galilean moons, but little else. Still, that’s again better than any
hand-held binocs.
Venus
shows its phase with no untoward flare and just a touch of chromatic
aberration, whilst you can tell Mars isn’t a star, but would struggle to guess
its phase (gibbous or full).
Deep
Sky
In
truth, the Pocket Borg really doesn’t do deep sky. Averted vision on the Double
Cluster? The Pleiades looked pretty good, with sharp stars, but lacked their
usual diamond-dust sparkle. Even a bright open cluster like M38 needed averted
vision to see more than just the faintest fuzzy patch.
The
Great Nebula in Orion (M42) looks much better in most binoculars because of
their greater light grasp.
Overall,
for portable deep sky you would be better even with a good pair of 8x32
binoculars … but of course they would be much bulkier and heavier to pack than
the Borg.
In
Use – Astrophotography
The
Pocket Borg doesn’t really have enough light or scale for imaging, but there
follows a shot of the Moon at prime focus through the Pocket Borg (no barlow or
Powermate) and then cropped. The result is better than I could achieve with my
Nikon 200mm lens, anyway and would have been sharper if focusing had been
easier (with their smallest helical perhaps).
Moon
through Pocket Borg: crop of original prime focus image, but with no PhotoShop
enhancements.
Summary
For
some buyers the Pocket Borg will doubtless be a route into a customised small
finder, perhaps by combining it with an erect-image diagonal or an
illuminated reticle eyepiece.
But
though I’d hate to think of children or beginners getting a Pocket Borg as a
starter scope, because it’s much too limited for that, it does have a use
beyond being a premium finder. For Borg have engineered this tiny scope with a
well-finished objective capable of higher magnifications and a properly baffled
tube, to create a sub-binocular sized setup that can do somethings
better than any hand-held binoculars.
If
not as a finder, then the Pocket Borg’s main use is as a travel scope for all
those times (let’s face it, most times) when you wouldn’t otherwise take any
scope at all. Whilst the 25mm aperture is seriously limiting for any kind
of deep sky apart perhaps from bright clusters like the Pleiades, there are
three reasons I can see for why you might want a Pocket Borg in your travel
bag:
1) First and
foremost, use it as a miniature daytime spotter in bright conditions and
at moderate magnifications. Pop it in your luggage at the last moment, then
deploy it on the patio table of your holiday villa, next to a glass of Barolo,
for distant views of that Tuscan hill town or smoking Sicilian volcano in the
distance.
2) When it’s
getting dark, turn the Pocket Borg on the Moon. No it isn’t going to let you
hunt for TLPs or Gruithuisen’s Lunar City, but the aesthetics of the view
–typical of small refractors - reward just gazing at a rising Moon over the
darkening sea at low power, without binocular shakes or softness. If you have a
short enough eyepiece, the Pocket Borg will show you a satisfying level of
quick-look Lunar detail at 30-70x.
3) For
quick looks at the planets, Pocket Borg also gives a more satisfying view than
binoculars. So if you’re still enjoying a quick observing session from your
Tuscan Terrace, you can see Venus’ phase, Jupiter’s main belts and moons,
Saturn’s rings.
The
only caveat is that to get powers above binocular level you will need an exotic
eyepiece or two, preferably something light like a Nagler zoom, to avoid
spoiling that travel portability.
I
cautiously recommend the Pocket Borg despite the severe limitations of its 25mm
aperture, but only as a travel scope in extremis – for those trips (for me
almost all trips) when otherwise the only distance magnifier to hand would be
miniature binos.