Vixen
60/910 L Achromat Review
This was the original (with a close
serial to prove it) guide scope on a beautiful veteran Vixen FL-102S set that I
was kindly loaned to review. But it was such a nicely made thing I decided to
unmount it from the rings and try it out as scope in its own right.
I discovered a very fine little long-f
achromat, worthy beyond the guide rings and capable of high powers. My guess is
that this is the same optic that Vixen once sold stand-alone as an L version.
At
A Glance
|
Telescope |
Vixen
achromatic guide scope |
|
Aperture |
60mm |
|
Focal
Length |
910mm |
|
Focal
Ratio |
F15.1 |
|
Length |
900mm |
|
Weight |
~1.8 Kg |
Data from Me.
Design
and Build
Thirty years on, Vixens from this era
are developing a following as classic small Japanese refractors. It's a bygone
era now, one when many amateur astronomers were at their happiest teasing out
detail on the Moon and planets through 0.965" Kelners and Orthoscopic eyepieces
with a narrow (but super-sharp) field, their eyeball glued to a tiny glass eye
lens.
This may be just a guide scope, but it
has the classic Vixen look from the 1990s and early Noughties, complete with
Hammerite green metallic accents like the standalone scopes from that era -
from modest achromats like this one, to apochromats approaching 5".
The build still has a
hand-made-in-small-batches vibe largely gone from astro gear now. However,
whilst build quality is good, it isn't at the artisanal level of a Takahashi
FC-60 (for example), nor honestly the slick mass-produced quality of many modern
scopes from China, but that IMO is part of the charm.
1990s Vixens shared styling and finish
cues, this one a 70FL.
Optics
The lens is
a Japanese made, air spaced (with foil spacers) achromatic doublet, with basic
crown and flint elements, same as millions of others. Coatings appear to be
high quality, but a single layer of magnesium fluoride, not modern multi
layers.
The
difference from many achromats of the time is that this one has a longer focal
length than most at 910mm, to give a full F15 that should mean very low levels
of chromatic aberrations at 60mm aperture. It's also, as we will see, very well
figured - notably better than most similar optics that I've reviewed (including
those from the likes of Unitron and Pentax).
The cell is fixed, unlike that of the FL-102 it came with
(though later FL objectives also did away with collimation adjustment).
Tube
The tube is
~65mm diameter and is otherwise like any other Vixen of the time, well finished
in glossy off-white enamel, flat-blacked inside and with a couple of knife-edge
baffles to kill stray light and improve contrast.
The lens
cell threads on, but it's basic screws for the focuser.
The long
focal length means this is a much longer OTA than a 60mm apochromat and much
less portable as the result, but it is very light at under 2 Kg.
Focuser
The cast
focuser with its chrome drawtube and green Hammerite finish and black
Vixen-typical plastic knobs matches the big scope. Smooth and image-shift free
it's a nice unit, but the drawtube is too narrow for a 1.25" eyepiece holder,
so it's 0.965" only.
Mounting
The original
guide scope mounting consists of two wide rings with long metal bolts to
provide support and adjustment. Fortunately for the tube, those bolts have
nylon tips.
To mount the
OTA separately, I reached for an FC-60/FC-50 Takahashi clamshell that looked a
similar diameter at 68mm; but unfortunately the tube is slightly narrower, so I
had to temporarily shim it with some felt.
The OTA is
long but light, goes on any small mount. Of course, a classic Vixen SP, GP or
DX with the matching green hammered finish would be ideal. At the time of
writing, nice examples of these mounts are still widely and cheaply available (cos y'all
want sine wave motors and goto).
Vixen SP
mount that came with the FL-102 set is a perfect match for the smaller OTA.
Accessories
The focuser
drawtube has a threaded end, but is only wide enough for a 0.965" eyepiece
holder. Back in the day, Vixen would have supplied some very decent 0.965"
Orthoscopic eyepieces with this if bought as a standalone OTA, but I don t have
a set.
Luckily, I
do keep a Takahashi 0.965" prism diagonal and a set of matching Takahashi MC
Orthos for this situation. I really like Tak's MC Orthos they're very well
made and coated, but come at a much more sensible price than Pentax's 0.965"
Orthoscopics which now seem to attract collector's prices (or maybe I'm just
sore cos I sold mine when they didn't).
I also
swapped out the set-screw eyepiece holder that you see in the pics for a
Takahashi twist-lock visual back from an FC-60 to avoid marking the diagonal
with Vixen's set-screw the threads matched.
Takahashi's
MC Orthos are highly recommended for 0.965" only scopes: better than circle V
and T, (much) cheaper than Pentax's.
In
Use Daytime
Not the kind
of thing you'd ever use as a spotter, it nonetheless gives sharp daytime views,
with very modest false colour in my usual 100x branches test.
In
Use Astrophotography
The 0.965"
visual back means I couldn't try any imaging.
In
Use Observing the Night Sky
General
Observing Notes
The focuser
has a narrow draw tube that makes it 0.965" only. I guess it had been little
used (if at all). The action is very smooth and free of shift, but as always
the grease had hardened to make it a bit stiffer than it would once have been.
A focal
length of 910mm is getting into the range where I prefer a finder, but there's
no way to mount one here. One advantage of that long focal length is that you
can use longer focal length eyepieces to achieve high magnifications (Orthos
suffer from terrible eye relief below 5mm): I only needed the 9mm and 7mm.
Unfortunately
the downside is a small field - the longest MC Ortho is 25mm and gives a minimum mag of 36x and a field of about a degree,
too narrow for the largest DSOs and asterisms.
Cool
Down
Small
doublets cool almost immediately and this one is no exception.
Star
Test
It's not
hard to make a slow, small achromat and this little Vixen proves it with a
perfect star test - identical rings either side, evenly illuminated and narrow - ironically, even slightly better than the expensive FL-102S it came attached to (though the FL s was still very good).
The
Moon
Small
achromats are lunar over-achievers and the 60/910 is no exception, giving a
sharp and contrasty Moon at 101x with a
9mm Takahashi MC Ortho, but with a purple fringe to the bright limb in focus
that apochromatic optics avoid.
Mars
At 101x with a 9mm Takahashi MC Ortho, Mars at 10.8" diameter showed a
proper gibbous disk, crisp and sharp, with a hint of albedo markings after
opposition in February 2023.
False colour here was different from a typical ED doublet: no red blur
out of focus or in the seeing, just a very faint and diffuse halo of deep
purple that I'd seen recently when viewing Mars with another long-f achromat
the 12" Zeiss at Griffith observatory!
The 60/910
guide scope even took the 7mm Tak Ortho on Mars, to yield a maximum practical
magnification of 130x with no false colour and sharp gibbous disk with hints of
albedo.
Deep
Sky
This kind of
telescope really isn't what you'd choose for deep sky, but with a 25mm Tak
Ortho the Pleiades just fitted in the field and looked nice and sparkly.
Another
classic use for long focal length achromats is double stars. Castor was an easy
split, but I couldn't convince myself I'd picked Rigel's dim companion from out
of the glare.
Summary
It's just a
guide scope after all, but production economics mean Vixen likely re-purposed
one of their 60L planetary achromats, so this is a super little scope for
planets, but for the Moon and easy doubles too.
Die-hards
might tell you a perfect long-f achromat like this gives the same view as a
60mm fluorite apochromat like Takahashi's FC-60 (a real favourite of mine). It
doesn't, quite. But it does come quite close for a fraction of the cost.
This is actually my first experience of a Vixen L achromat the long
focal length editions they made of their small achromats from the Nineties,
aimed at the planetary and lunar observer. If this one's anything to go by,
they're well worth seeking out if portable planets are your thing.
Just a 60mm achromat, but a beautifully
made (in Japan) one, with near-perfect optics.
