Takahashi FC-76Q (FC-76DCU + EX-CQ)
Review
The
FC-76 manual has this strange addition to its system diagram. It suggests that
you can thread the CQ module 1.7x extender from the FS-60Q into the FC-76 to
create another variant of what has become a modular telescope system for the
Takahashi 60mm and 76mm objectives.
Of
course, to do this you need the version of the FC-76 that threads in half. This
used to mean combining an FC-76 objective unit with the focuser end of an
FS-60, but now you can buy a complete split-tube FC-76. In either case, the CQ
module just threads between the objective and the focuser tube.
Why
might you want to do this? After all, the CQ extender exists to cure the
FS-60’s less-than-perfect high-power performance; but the FC-76 is already a
very good performer at high powers (i.e. for the Moon, planets and double
stars).
The
answer might be that the FC-76 is still slightly compromised. Compared with the
old FS-78 (a superb planetary scope), the FC-76 has just a bit more chromatic
aberration, is just a bit softer on Mars and Venus. The CQ module should fix
these minor issues and give a larger image scale too.
“But
why are you reviewing it separately?” you ask.
Part
of the answer is that – just like the FS-60Q – the FC-76Q is a very different
animal from the FC-76, so worth its own review. And apparently (according to a
major Japanese dealer), lots of people are doing this by buying the split FC-76
and the CQ module separately.
The
other part of the answer is simply that that Takahashi do sell (or once did)
the FC-76Q as a separate product. In May 2016, they released thirty FC-76Q sets
for the upcoming Mars opposition, noting:
Takahashi’s
original announcement of the FC-76Q for the 2016 Mars opposition.
At A Glance
|
Telescope |
Takahashi
FC-76Q |
|
Aperture |
76 mm |
|
Focal
Length |
954 mm |
|
Focal
Ratio |
F12.6 |
|
Length |
810mm |
|
Weight |
2.1 Kg
(2.7 Kg incl finder, ring) |
Data
from me.
What’s in the Box?
Shown
is the unboxing for the FC-76 objective unit, which is the way I did this:
The
other two Takahashi ‘Qs’: FOA-60Q (top), FS-60Q (bottom).
Design and Build
The
FC-76Q is following a path started by the FS-60Q and most recently continued by
the FOA-60Q (see above).
Take
a doublet refractor of moderate focal length and thread an extender ‘module’
into the OTA to create a longer focal length whilst improving correction and
coverage right out to full frame. Result - a super-sharp visual scope or a
large image scale and highly corrected field for imaging of small DSOs,
eclipses etc. Then market the new scope as either an upgrade or a complete OTA.
Here’s
that excerpt from the FC-76 manual:
Optics
The objective is obviously just the same as the
standard scope, i.e. it’s a Steinheil doublet that
puts the fluorite element at the back, like the original FC-76. This helps
protect the delicate and hygroscopic Fluorite. Like other Takahashi objectives,
this one was made by Canon/Optron in Japan. A laser
test confirms that this is a foil-spaced design (you can just see the spacers):
there is no significant air gap.
The standard FC-76 has an f-ratio of F7.5, giving a
focal length of 570mm. The CQ module extends that to 954mm (F12.6), a long
focal ratio for an apochromat, but slightly shorter than the FOA-60Q which is F15.
The CQ module is a doublet that sits half way down
the OTA making the overall optical system a quadruplet. This configuration
makes the module an integral part of the optical system, unlike most extenders
that go in the focuser tube. Result? It feels like a complete scope, not a
bolt-on.
The FC-76Q weighs in at 2.7Kg including finder and
ring – about the same as the FOA-60Q.
Tube
It’s a strange looking tube - very long at 810mm and
thin with two segments, but it all fits together just fine, then looks and
functions like an item.
The CQ module adds just 300g, so total weight, at
just 2.1 Kg for the bare OTA, is still low (the old FS-78 added half a kilo to
that). It all disassembles into short (~300mm) pieces, so no problem with
transport. The long tube makes for more vibes than the standard FC-76 though,
meaning it works better on a beefier mount.
Focuser
Of course, this is just the standard FS-60/FC-76
focuser with its 2” (50mm) drawtube. It’s compact, accurate and very smooth,
takes weight well and has an excellent brake. This one is largely free of image
shift, too.
But
in one way, I am surprised that Tak released this
combo as a production scope, because the
1.5” available focus travel just isn’t enough for all eyepieces. With a
1.25” diagonal, there’s not enough back focus, but with the shortest extension
there is too much. Meanwhile, a 2” diagonal works for some eyepieces, but not
others. You could easily cure this problem with a longer drawtube focuser
(perhaps a 2.5” drawtube Moonlite).
Mounting
The FC-76Q is light enough to go on my Vixen SX2
without any counterweight (the SX2’s motors act as a counterbalance). It will
still mount and balance on the Takahashi Teegul
micro-mount, but only with light accessories and even so it’s more shaky than
usual and strains the little RA motor. Driven Manually, it is perfectly usable
on the Teegul though, if a bit vibey at high power.
Accessories
Takahashi
sell a nice logoed soft camera-type case in Japan that would take all the OTA
parts when broken down, but it suffers from the usual Takeyourcashi
problem at around £250 imported.
As
usual you can fit various Tak’ finders, but the outstanding
6x30 unit is the one you’ll likely pick because it’s much cheaper and smaller
than the 7x50 and has more eye relief as well (though no illuminator option).
In Use – Daytime
Viewing
my local Jackdaws roosting in high branches against a bright sky, generates too
much contrast for many so-called apos, forcing them
to line branch and feather with purple and green chromatic aberration. But with
the FC-76Q at a ridiculous (by spotting scope standards) 161x with a 6mm Ethos,
a whole Jackdaw fills the frame – pin sharp and false colour free. Even
focussing through I can detect only the very merest trace of colour.
Using
the FC-76Q as a telephoto lens is a stretch, physically and thanks to the slow
f-ratio, but daytime shots are flat, super sharp, full of detail and with
almost no false colour at all.
Note
the ‘almost’ no false colour. That’s significant, because in daylight viewing the
FOA-60Q has none, really, just none (and the FOA employs a lot of extra optical
tech’ to get rid of that last smidgen of chromatic aberration).
In Use – Astrophotography
I
was just astounded at the image of the Moon I got with the FC-76Q. Part of the
goodness is just down to increased Image scale, but the detail on an evening of
fairly steady seeing was outstanding – by far the most detailed image of the
Moon I’ve taken with a scope of this size. The image is sharp from limb to limb
too, due to the flattener effect of the CQ module. In fact, the FC-76Q
<might> just have produced the best single-shot Lunar images I’ve taken.
For
deep sky, it’s slow at F12.6, but after that the news is all good.
On
an APS-C sensor it is flat to the edge with excellent coverage. Stars are
pinpoint and show almost minimal blue-violet bloating. The extra image scale
actually works well for smaller DSOs, where one minute
exposures at ISO 3200 would give good individual frames to stack.
At
full frame, stars are still undistorted to the edge; coverage drops only in the
very corners (and that might be improved with a wide T-mount). Compared to the stock
FC-76, both flatness and coverage are much improved, but violet bloat appears
the same (i.e. minor, but present). Interestingly, coverage is slightly better
than the FOA-60Q, but again a wider T-mount might fix that.
As usual, the images below are single unprocessed
frames (why? Because my skills – or lack thereof - with MaximDL
and Photoshop are irrelevant).
M57:
58s ISO 3200 Fuji X-Trans APS-C.
M1:
102s ISO 1600 Canon EOS 5D.
Moon:
1/320s ISO 1000 Fuji X-Trans APS-C (cropped).
In Use – The Night Sky
General Observing Notes
The longer focal length (and so smaller field of
view) makes finding things a bit harder, but maximum FOV is still double that
of an 8” SCT – 1.6° with a 1.25” eyepiece, 2.8° with a 2”.
My impression is that the shallower light cone and
larger focusing sweet-spot make the FC-76Q less sensitive to seeing than most.
This is a real bonus for objects low in the sky. Given how low the planets have
been lately, this might be a killer advantage compared to most fast
apochromats.
Cool Down
As you would expect, the extra glass and longer tube
means cool-down is slower than the basic scope, but probably still faster than
a 3” triplet.
Star Test
My FC-76 already has a good star test and adding the
module retains it, with near identical rings either side of focus, although the
outer ring is more diffuse – an effect of the module, same as both the FS-60Q
and FOA-60Q.
The Moon
Even my first view of the Moon at just 40x was a
‘wow’ moment – so razor sharp and clean that I immediately knew this was
something a bit special. In good seeing on a 1st quarter Moon at
193x with a 5mm Nagler, the view is perfectly crisp
and sharp, if just a little dim. There is no chromatic aberration. At that
magnification the Moon is a lot more involving than the usual lower
magnifications I use with a 3” refractor.
Venus
At 193x with a 5mm Nagler,
the view of a crescent Venus is quite simply one of the finest I have ever had:
absolutely crisp, with no unfocused light and no false colour at all, even
focusing through.
Venus presents a problem for many otherwise excellent
small apochromats, but not for the FC-76Q.
Mars
In good seeing, a tiny (3”) Mars shows as a perfect
disk at 193x, again with no flare or softness. This is an improvement over the
base FC-76, which is OK on Mars but still a little softer than the very best.
Jupiter
Likewise,
Jupiter is razor sharp and shows the most detail you are going to get at 3”
aperture, with excellent contrast.
Deep Sky
Surprisingly, the FC-76Q is unreasonably good for
deep sky, just as I’ve found the other ‘Q’ Taks are.
Why? Not sure, perhaps the perfectly corrected lateral field just works well
for extended objects.
The 1.6° field of a 32mm Plossl
easily fits the whole Pleiades in and it’s maybe the best view I’ve had in a
small scope – pin sharp stars with wonderful true colours, lots of nebulosity
and a really flat field.
M37, an open cluster in Auriga, is magnificent with
a diamond dusting of perfect tiny stars. The Dumbbell Nebula is again as good
as I’ve seen it, ditto the Ring nebula in Lyra. I start to explore and find
other objects, such as M56 and M1, a bit dim. But then I remind myself that
this is just a 76mm scope, not the 175mm it’s sitting on top of!
It’s a similar story with doubles: picking likely
candidates from the ADS catalogue using GOTO, I find that brightness not
resolution is the main barrier. Still, epsilon-lyrae
(the Double Double) is super-easy; again the best I’ve
seen in a sub-100mm scope.
The FC-76Q edges
noticeably ahead of the standard FC-76 (and perhaps even the old FS-78) on the
Moon and planets. Surprisingly, with its tight stars, very low false colour and
really flat field, it’s great for deep sky too (within its aperture
limitations, obviously).
Summary
Even
more than the FS-60Q, the FC-76Q is a slightly weird scope. But just like the
FS-60Q and FOA-60Q, it is simply outstanding at higher powers and image scales.
The view is pin sharp all the way across. False colour is in the super-apo
league. It beats every other (really) 3” refractor I have tested on the Solar
System. The integral extender makes for a much better scope than any barlow-type device that plugs in the focuser.
It’s
not just about image scale and centre-field resolution: the CQ module works as
a flattener too, so extended Lunar (and so by extension eclipse) images are just
stunning.
So,
if you need a really portable (it will still just go on my little Teegul mount) planetary, Lunar or eclipse scope, this might be for you. Then again, for
imaging it may be slow but the field is super flat, blue-bloat almost absent
and coverage excellent. It’s (surprisingly) a really nice visual deep sky scope
too, perhaps because of its pin-point stars across the whole field.
If
you have an FC-76 objective unit already, all you need is the CQ module. But if
you are buying an FC-76DC from scratch and think you might want to do the CQ
module thing in the future, you need to wait for the FC-76DCU version that has
the split tube and is supposed to be replacing the existing FC-76DC.
Don’t buy the CQ module for your standard FC-76, it
won’t work!
The
FC-76Q looks like a lash-up, but it really works and then some. For the
peripatetic planetary observer or eclipse imager, it’s brilliant. If you have
an FS-60+FC-76 objective unit (or an FC-76DCU) already this is a highly recommended
upgrade.
By
Roger Vine 2018
