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.
Partly the answer is simply that that Takahashi make (or once made) the FC-76Q as a real product. In May 2016, they released thirty FC-76Q sets for the upcoming Mars opposition, noting, “it is recommended for the observation of Mars”.
The other 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. Now I’ve tried it, I know why! Read on …
At A Glance
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:
Design and Build
The FC-76Q is following a path started by the FS-60Q and most recently continued by the FOA-60Q.
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:
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 indicates that this is a foil-spaced design: 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.
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.
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.
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).
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.
Takahashi sell a nice soft camera-type case in Japan that would take all the OTA parts when broken down. As usual you can fit various Tak’ finders.
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.
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.
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).
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.
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 Mars will be around opposition in 2018 and 2020, this might be a killer advantage compared to most fast apochromats.
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.
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 the FS-60Q.
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.
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.
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.
Likewise, Jupiter is razor sharp and shows the most detail you are going to get at 3” aperture, with excellent contrast.
The FC-76Q is unreasonably good for deep sky. 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 star 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).
Even more than the FS-60Q, the FC-76Q is a slightly weird scope. But just like the FS-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.
It’s worth pointing out that Tak’s new ortho-apochromat FOA-60Q uses a similar layout to produce (apparently) one of the most perfectly corrected refractors ever made. It’s important to stress that the Q module is nothing like a mere barlow, or indeed any post-focuser extender.
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, 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 sounds 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