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.
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.
