Takahashi FOA-60Q Review
Takahashi’s
original ‘Q’ scope, the FS-60Q, uses an inline
extender/flattener to turn the FS-60 imaging scope into a mini super-apo for
the solar system. It is one of my favourite small refractors. It’s ideal
for eclipses, but makes a great terrestrial telephoto too. The FOA-60Q on test
here uses a similar module to convert the FOA-60 into … well, what
exactly?
You
see, unlike the FS-60, the FOA-60 is already one of the most perfectly
corrected refractors with a long focal ratio of F8.8. What value could an
extender module really add? On the face of it, the FOA-60Q is a bit of a
puzzle. I’ll let Takahashi explain:
“The
FOA-60Q has the highest optical performance among all Takahashi optical
systems. It boasts the World’s highest level of optical performance,
maintaining a Strehl ratio of 99% over the entire visible light range and the
entire field of view of a full-size camera.”
Those
are quite some set of claims. Indeed, they need to be given that the FOA-60Q is
getting on for the price of a Tak’ FC-100DC or a Mewlon
180.
Takahashi
go on to add that the FOA-60Q is thus ideal for observations of the Moon and
planets, for corona imaging of solar eclipses and as an “ultra-high
performance super telephoto lens”.
In this
review, I’ll put all that to the test, but at this stage you could fairly
call me sceptical.
Two Qs:
FOA60Q and FS-60Q: note the red serial plates for quadruplets.
At A Glance
|
Telescope |
Takahashi
FOA-60Q |
|
Aperture |
60mm |
|
Focal
Length |
900mm |
|
Focal
Ratio |
F15 |
|
Length |
540mm/600mm
dewshield retr/extd |
|
Weight |
~2.4Kg incl clamshell |
Data from Me.
What’s in the Box?
Typical nested Takahashi boxes:
Design and Build
The
FOA-60Q is based on the FOA-60 and that means it’s a premium Tak’
with a slightly retro vibe: the
tube is the same 68mm diameter as the classic FC-60 and FC-50 (yes, their
clamshells fit, I checked) and the tiny cast focuser looks to be the same too.
But where the FC-60 had a fixed dewshield, the FOA’s is a sliding affair
with a lock screw. Did I mention it looks good, with the long slim tube and
proper lens hood? Much better, in my opinion, than the Vixen-FL-like FS-60Q.
The
livery is Takahashi’s latest – i.e. bluish green powder coat for
the focuser, a slightly off-white gloss tube and a matte silver lens ring.
A note
on serial-number plates: you could convert a blue-serial-plated standard FOA-60
by buying the Extender 1.7XR. Alternatively, you can buy the complete FOA-60Q
with the module installed, in which case you get a red serial plate, same as
other quadruplet Taks (in case you’re wondering, triplets get a green
plate). That’s how I bought
the one on test here.
The
FOA-60Q is a quadruplet and gets the red plate, same as an FSQ.
Three
generations of Takahashi long-focal-length 60mm apochromat: FC-60 (bottom),
FS-60Q (mid), FOA-60Q (top, shield retracted).
FOA-60
front-surface fluorite Doublet lens.
Collimation
screws on the back of the cell, usually hidden by the lens ring.
Laser
test confirms a front-surface fluorite doublet with a very large air gap.
Optics
The
FOA-60Q claims to be perhaps the most perfectly corrected apochromat ever made.
How does it achieve this?
The
base FOA-60 is already pretty special. It uses a front surface fluorite crown along
with some kind of special high-dispersion flint glass mating element and a
large air gap (see above) to create a doublet that’s competitive with
their triplet ortho-apochromats (TOA-130 and 150) for chromatic aberration.
The
FOA-60 lens cell is large and collimatable (the
collimation screws are on the back, hidden by the lens ring). The inside is all
ridged and blacked like a premium camera lens.
The
‘Q’ then adds in a doublet flattener/extender module – the
1.7XR – to further correct the following remaining limitations of the
base FOA-60:
·
A trace
of centre field chromatic aberration
·
Edge
chromatic aberration
·
Field
curvature and vignetting, esp. across larger sensors
·
Some
residual spherochromatism (variation of spherical aberration with wavelength)
The 1.7XR
extender for the FOA-60 is similar to the Q module for the FS-60Q. It also has
a 40mm doublet lens, but a different tube size (68mm vs 80mm) and it is considerably
more expensive. As with the other ‘Q’ module, the lens has superb
multi-coatings and should absorb very little light.
With
the module in place, the F8.8 doublet of the FOA-60 becomes a quadruplet
optical system at F15 (900mm focal length).
The
result is a scope that corrects false colour almost to reflector levels.
Perhaps more importantly, spherochromatism – variation of spherical
aberration, i.e. optical quality, by wavelength - is basically eliminated for
all visible light as well.
For
imaging, the ‘Q’ module confers a flat and well-illuminated field
across a full-frame sensor for virtually the whole visible spectrum. This being
Takahashi, they’ve backed those claims up with some graphs and spot sizes
that I’ve re-printed below.
To get a handle on just how theoretically excellent
the FOA-60 is, I have also collated Takahashi’s published centre spot
diagrams for a few of its ‘planetary’ refractors, along with a
basic FS-60C for comparison. As you can see, the base FOA-60 – even
without the ‘Q’ module in place - achieves tighter control than any
other Takahashi refractor, even including the outstanding TSA-102 (a now
discontinued F8 triplet) and the very latest FC-100DZ.
The poly-strehl
(spherochromatism) graphs for the FOA-60Q and FC-100DZ are also telling: the
‘Q’ is way better, almost perfect as claimed.
FOA-60 Extender 1.7XR Module with 40mm lens.
Some spot diagrams for Takahashi fluorite
apochromats compared.
Spot diagrams for FOA-60 and new FC-100DZ compared.
Poly-Strehl graphs for FOA-60Q and new FC-100DZ.
Note that the FC-100DZ is already very good in this respect.
Tube
The ‘Q’ borrows its 68mm tube from the
base FOA-60, which in turn derives it from the old-skool
small Taks, the FC-60 and FC-50 (the super-rare FCT-65 too). Physically, you turn an FOA-60 into an FOA-60Q by unscrewing
the focuser and inserting the 1.7XR module between it and the FOA main tube.
The threads seem very well machined, but they are fine and would be easy to
cross-thread, so I always thread them carefully and with the tube vertical.
The
sliding dewshield has a large thumbscrew to secure it and runs easily, locks
with a satisfying thunk. It’s a generous length and has some micro-ridge
baffles at the front – another little premium feature.
Inserting
the extender changes the optical character; the physical character too. The
FOA-60Q is quite a bit longer than other Takahashi 60s: 540mm long from the
2” visual back (the 1.25” insert adds another few cm) and with the
sliding hood retracted. Extending the dewshield takes it to 600mm in length.
For a
60mm, it’s quite heavy too at ~2.4Kg including the clamshell. The FOA-60Q
is almost as heavy as an FC-100DC, heavier than the FC-76DC. By comparison, the
old FC-60 was just 1.5Kg incl. its ring.
The FOA tube has a single knife-edge baffle, one
area where the old contrast-monster FC-60 beats it with three.
Dew-shield retracted …
… extended.
FOA-60Q focuser at full extension, showing 2”
visual back with slot-in 1.25” adapter.
Focuser
The
focuser appears to be the same unit as the old FC-60 and FC-50. It looks tiny,
much smaller even than the FS-60’s, but it has a full 84mm of travel to
accommodate most eyepieces without an extension. For photography, Tak’
provide a quality 2” extension (also useful for Japanese style
straight-through viewing).
The
FS-60Q, like the old FC-60 and new FC-76, has the cheapo hollow-plastic
imitation focuser knobs, but the FOA-60 gets the proper anodised silver metal
ones like other Tak’s. The matching silver knob on top of the focuser is
the standard Takahashi lock: progressive and shift-free.
The
focuser tube is the same slim 45mm silver one as the small FCs. Back then, that
limited those scopes to 1.25” accessories. But the FOA visual back
differs from the FC-60’s - it terminates in an adapter and 2”
eyepiece holder. On the FC-60 the visual back threaded on, but in more recent
models like the FOA the 1.25” visual back just slots into the 2”
one. Like all Tak’ 2” VBs, there are twin set-screws, not the
lock-ring you get with the 0.965” or 1.25” visual backs. If you did
want to go all retro, an old 0.965” FC-60 visual back simply threads into
the adapter.
The
focuser tube is all concentric ridge baffles and camera-black inside to kill
stray light. Takahashi extend the premium build to parts that aren’t on
show.
Despite
its small size, the focuser takes larger eyepieces fine and remains smooth and
shift free with a camera. It started out a bit stiff, but accurate and with no
slop. It has gradually eased up to become a typically butter-smooth Tak’
focuser, although still stiffer and less fluid than the identical unit on my 30
year old FC-60, which has probably the smoothest focuser I have ever tested
(yes, even smoother than a Feathertouch).
Mounting
Though the FOA-60Q is well within the weight limit
for the miniature Takahashi equatorial mounts, the Teegul or PM-SP, it is long,
which means it vibes a lot more than an FS-60C or even an FC-76DCU. For high
power use as designed, you need a heavier mount. Much of my testing was done on
a Vixen SX2.
FOA-60Q on Vixen SX2 (no need for a counter-weight).
Takahashi’s excellent 6x30 finder.
6x30 finder view: sharp, flat, wide and with loads
of eye relief.
Accessories
As explained above, a 2” visual back as
standard, as is a 1.25” adapter with the traditional Tak’
twist-lock and silver plug. A quality 2” extension is also provided for
imaging and straight through viewing. But that’s it for standard
accessories, unless you buy the complete package.
The package will include Taks’s
excellent 6x30 finder. If you hate optical finders this unit will change your
mind with pin-sharp optics, a huge field and loads of eye relief.
Unlike the FC-60, the finder mount is the standard
one, so alternatively you could go the whole hog and buy the 7x50 unit with the
illuminated reticle. Yes, it’s the price of a
decent small Chinese apo, but it’s only money, right?
The package also includes a clamshell. As I noted
already, the FC-60 and FC-50 68mm clamshells fit fine, but the
‘proper’ one for the FOA-60 is a little different, having mounting
holes on top for the GT40 guider. But the base is the same – twin M8
holes at 35mm separation like always (except now there is another pair at right
angles for side-by-side on a big plate).
In Use – Daytime
Weird. Almost supernatural. I mean, look, when I
reviewed Swarovski’s state-of-the-art 15x56 HD binos
I marvelled at the sharp false-colour-free views of silhouetted feather and
branch … at 15x. Now with the FOA-60Q you can multiply that by ten to
create a kind of long-distance microscope.
Viewing birds, berries, leaves or whatever,
highlighted against a sunny sky at 150x with an Ethos 6mm eyepiece, the view is
totally sharp – like being a few centimetres away. What’s more
there is no hint of false colour, none: not in focus, not focusing through.
Only now can you really appreciate how much false colour other
‘apochromats’ leave in.
Consider that my usual apochromat test is viewing
silhouetted branches at 100x. Most refractors fail it, some extravagantly.
Indeed, anyone who has used a normal spotting scope will appreciate how
extraordinary viewing in crystal clarity at 150x plus really is. Photos
can’t convey that perfection, but I’ve tried with a snap taken with
my phone through the Ethos 6mm.
Ordinary views not in silhouette are just as
sensational. I watched insects crawling across a trunk 200m away in close-up
HD. And the view is sharp and colour free right to the edge. But you do need a
superb, low-aberration eyepiece like the Ethos (£500 each) to do this
– my Naglers don’t really cut it at this magnification during the
day.
Practically, though, there is another problem
– the FOA-60Q is big for a spotter and at those magnifications you need a
very stable mount. You could take the FOA-60Q out for nature photography, but
you’d a big tripod and cine-head.
Snap of needles 200m away at 150x with FOA-60Q,
taken through an Ethos 6mm eyepiece with an iPhone camera.
In Use – Telephoto
Like the FS-60Q, the FOA-60Q makes an outstanding
telephoto lens, in this case 900mm F15.
Coverage on APS-C is perfect. On full frame, the
image is absolutely sharp right across. Vignetting is only evident in the very
corners and a wide-T mount might prevent even that. Resolution at full frame
with my EOS6D Mark II is just superb.
As usual the images below are straight from the
camera, just re-sized.
Full frame: Canon EOS 6D Mark II with FOA-60Q, 1/80s
ISO 200.
Crop of centre section of full frame image above at
actual size.
APS-C: Fuji X-Trans with FOA-60Q, 1/250 ISO 800.
Crop of extreme RH corner.
Prime focus shot of berries. Again, Straight from
Fuji X-Trans camera.
Crow in flight with FOA-60Q: no false colour.
In Use – Astrophotography
An aperture of 60mm at F15 doesn’t sound
promising for astro-imaging, but with a very flat field, wide coverage, minimal
violet bloat and large image scale, the FOA-60Q has some real applications.
Below are some sample subs straight from the camera to show what’s
possible. As expected, images of the Moon and planetary nebulae are
particularly good.
Coverage would likely be even better with a
Takahashi (or Borg) wide-T mount.
M1 at full-frame: 180s at ISO1600 with Canon EOS 5D
and FOA-60Q.
Crop of Moon with FOA-60Q: slightly increased
contrast, otherwise un-retouched.
In Use – The Night Sky
General Observing Notes
Visually,
even the brightest O-A stars like Vega and Sirius show no false colour, none at
all, even in the star test. This is a truly chromatic-aberration-free
refractor. Again, it’s almost odd. It’s also chastening to consider
how far you have to go (a fluorite/ED quadruplet 60mm F15!) to get a refractor
to do what comes naturally to mirrors.
With a perfectly corrected eyepiece like an Ethos
(or even Nagler), the FOA-60Q delivers beautifully pin-point and aberration
free stars right across the field; this is unusual and again a little
unnatural.
One
really striking feature is the FOA-60Q’s ability to cut through bad
seeing. On one night I was enjoying a setting first quarter Moon only
10-12° above the horizon. The FOA-60Q was delivering super-sharp and
detailed views at 100x with 9mm Nagler; I easily resolved Hyginus crater and
caught glimpses of the rille. But turning to my other scope, the Moon was a
mess of boiling air.
Cool Down
All
that glass means cooldown is noticeably a bit slower than a doublet, but still
fast compared to other types. It’s usable straightaway, but actually only
delivers its finest views after perhaps ten or fifteen minutes. This was
apparent when I tried splitting Epsilon-Lyrae straight from the house.
Star Test
Independent bench tests have measured a random
sample of the base FOA-60 lens at 99% Strehl. However, the ‘Q’ star
test, like the FS-60Q, was slightly off – quite under-corrected. Complex
optical systems with aspherical surfaces can show this in the star test. In
practice, there’s no question this is an outstanding optical system.
The Moon
The FOA-60Q delivers the coldest hardest whitest
Moon you’ll ever see (in a refractor anyhow). No false colour anywhere.
You don’t notice this in an image, but you do visually. There is no smear
of lilac around highlit peaks or shadowed craters at
all. Focusing through the bright limb of a nearly full Moon – centre
field to avoid eyepiece effects – yields no trace of colour at 180x; an
FC-60 alongside generates the merest hint of gold and dusky-rose either side of
focus.
A 3-day crescent Moon fills a 7mm Nagler Type 6 at
129x. The Moon is low and from my other scopes I know seeing is poor, but the
FOA-60Q still gives a good view, confirming that long f-ratios do work better
in turbulent seeing. Mare Criseum looks really
involving and mysteriously explorable, even at this tiny aperture –
impressive.
At 180x with a 5mm
Nagler, examining Mare Imbrium and Theophilus on a different night,
there’s no sense that this is more power than the Q can handle. Swapping
to the same magnification but with a 10mm Zeiss Abbe Ortho in the Zeiss 2x barlow definitely
sharpens things up and reveals more detail. I notice how little light bleed
there is off the limb into black space.
Dropping back to 69x with
a 13mm Panoptic give a real wow moment, a stunning view of the whole Moon with the
star Propus in Gemini hanging a firey
orange just off the limb. The view reminded me of my TMB175 with a 13mm Ethos
– a perfect hard white and grey orb in miniature, full of sharp detail.
One of the finest views of the whole Moon I’ve ever had.
One frosty November
morning of excellent (8-9) seeing gave me a last quarter Moon, high in the sky
just off the meridian, with Albategnius on the terminator. The ‘Q’
was in its element. A 5mm Nagler giving 180x showed a wealth of sharp detail. I
could make out the craterlets like a string of beads along Rima Hyginus,
normally the preserve of larger scopes. The view was just like a good 100mm
apochromat, reminding me of a similar morning with an FS-102 years ago.
Incredible for a 60mm.
Traversing the
terminator, I wanted to forget the review and just view. Mons Piton alone in
the mare, bathed in evening light. The sharply defined peaks of the Apennines.
Rima Ariadaeus full of shadow and running off into the lunar night. Alphonsus
with its offset central peak and hummocky ridge, where Ranger 9 impacted in
1965. The Straight Wall and its odd arrow-head at one end. The slumped walls of
Tycho in extraordinary detail. Clavius and its arc of craters.
I don’t generally like
excessive magnification, but the ‘Q’ could clearly take more. So,
I upped to a 3.5mm Nagler, giving a ridiculous (for a 60mm) 257x. Yet the
view remained incredibly sharp, with no break up or softening, the kind of
‘Lunar Module porthole’ view I have only experienced in much larger
scopes. I spent ages flying over the rugged shadows of the terminator,
struggled to quit the eyepiece in the end. Takahashi promised the ability to
take exceptionally high magnification; they delivered.
The FOA-60Q is a fabulous
lunar scope for its aperture.
Jupiter
At 150x
in a 6mm Nagler zoom, Jupiter showed an excellent image with absolutely no
false colour and no softness or stray light. But then I swapped to a Zeiss Abbe
Ortho’ 6mm. Usually the difference would be very subtle; but in this
case, Jupiter sharpened considerably with more contrast and detail, revealing
NEB and SEB, polar hoods and hints of darker storms – impressive detail
for a 60mm.
Mars
A
low and tiny Mars, at just 13 degrees altitude early in an opposition year was
nonetheless a hard, tight ball with no softness or CA.
I revisited Mars with the FOA-60Q two
days after the 2020 opposition, with Mars still at 22” and in excellent
seeing. A 7mm Nagler T6 giving 129x showed the tiny southern polar cap,
featureless (to a 60mm!) deserts of Tharsis in the north and significant albedo
detail in south including the ’Eye of Mars’, the Solis Lacus
region. Upping to 180x with a 5mm showed no extra detail, but stayed perfectly
sharp and crisp with no loss of contrast or softening, no false colour in or
out of focus.
The FOA-60Q gave a very similar view
to the base FOA-60 at similar mags on the same night, but impressively I
thought it delivered just a little more contrast, as even sharper high mag’
image. But perhaps that was just because the longer focal length and thus sweet
spot made finding perfect focus a little easier.
Deep Sky
At 129x with a 7mm Nagler, the Double Double was the easiest and cleanest of splits I’ve
seen in a small scope, in decent seeing just after dusk.
Whilst slow focal ratios mean longer exposures,
it’s a myth that slower scopes are dimmer for visual. In fact, the FOA-60Q’s
ultra-high strehl should mean tighter brighter stars
and that’s how it seems to work out. With plenty of field width in a 32mm
Plossl to accommodate them, the Pleiades are
especially brilliant and diamantine, shining in a silvery mist of nebulosity.
I find the Ring Nebula, swap to an 18mm Takahashi
MC Orthoscopic and … wow! I can’t remember seeing the Ring so
clearly defined, like floating smoke, through a small aperture before. I hunt
down the Dumbbell and it seems even more so, hanging with an almost 3D solidity
and separation in black space. The 18mm MC Ortho quickly became my favourite
deep sky eyepiece in the FOA-60Q, with loads of eye relief, no blackouts and
incredible transparency and contrast.
Next up are two bright globular clusters –
M15 in Pegasus and M13 in Hercules. M13 in particular seems brighter than
I’ve ever seen it in a 60mm refractor and with averted vision I can start
to resolve the mass of outer stars. M15 is smaller and dimmer, less resolved,
but looks good too.
The FOA-60Q’s good deep sky performance (for
a 60mm obviously, this is no Big Dob!) is notable,
likely down to its tight star images, flat field and top-quality coatings.
Summary
When I started work on this review, I’ll admit
I was pretty sceptical. Why would anyone want that level of perfection when the
basic FOA-60 is already very good, as is the cheaper and lighter FS-60Q?
Now I’m converted, excuse the pun.
Sure, it’s only a 60mm refractor, but there is
no other telescope I know of that will do what the FOA-60Q can do. Perfect
views of birds roosting hundreds of metres away at 150x is extraordinary. Views
and images sharp to the very edge are amazing too. Ditto sharp lunar views
still sharp at 257x (!)
Most amazing of all is that, visually and for
daytime telephoto at least, this is truly an ortho-apochromat, with no
discernible false colour at all under any circumstances. Daytime telephoto
images are outstandingly good, even at full frame.
Who but Takahashi would dare build such a thing and
sell it to the public? App-driven automated imaging scopes are one type of
progress; pure optical innovation like this is another. But I fear that if we
lose the high-end manufacturers like Takahashi, the latter will stop.
Of course, whether you need the singular optical
wizardry of the FOA-60Q is up to you. In ordinary circumstances for astronomy
you will notice no difference compared to other fine 60mm apochromats. But on
the right occasion, with perfect seeing, the FOA-60Q has the power (literally)
to amaze. Or if you need a terrestrial super-telephoto at sensible cost, this
is a serious option.
The
FOA-60Q is certainly a specialist telescope, but it’s far from a
pointless exercise as I had feared. Performance, for visual or imaging, day or
night, is just outstanding. For specific uses and connoisseurs of fine optics,
the FOA-60Q is highly recommended.
