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Takahashi FS-60C and FS-60CB Review

FS-60CB with 6x30 finder.

FS-60C with 5x25 finder. Note the slightly longer tube.

I have a real weakness for tiny, high-quality refractors and I’ve wanted an FS60 for years. Somehow, though, I’ve managed to own most of the others in the FS range, but not this, the smallest … until now.

Tiny refractors like this work on a number of levels. For one thing, of course, they are very portable and cool down almost instantly. So they are ideal for travel and quick looks.

There is a more serious side to small refractors though – the short focal length makes some very wide-field astro-photography possible. Why not just use a camera lens? Well for a start 355mm is still a pretty large lens and for another, camera lenses often produce less-than-perfect star images when you really zoom in.

The thing about the FS-60 that differentiates it from the mass of other small APOs, though, is that with it you can build a complete multi-role observing/imaging system. Takahashi make a host of reducers, flatteners and extenders to change the optical parameters of the FS-60, including the recently introduced ‘CQ 1.7x Module’ which threads in behind the objective and turns an FS-60C into an FS-60Q, a micro super-APO for the Moon and planets. I will be posting a complete review of the FS-60Q in a separate article.

I have revised this review in light of my second FS-60 – an FS-60C built in 2006 - which is rather different from the first, a 2009 model FS-60CB.

Design and Build

Optics

The FS-60 is the last descendant of a once noble line of Takahashi FS refractors that also included 3”, 4”, 5” and 6” models, all now long-discontinued. The ‘FS’ stands for front-surface fluorite: these doublets all have a fluorite element at the front, something which I think adds a bit to contrast. Why more contrast? Because fluorite transmits more light and scatters less than any optical glass. Strangely, Borg is now using front-surface-fluorite Optron lenses in its recent small refractors like the 50FL, 67FL, 71Fl and 90FL (and very good they are too).

Unlike other telescopes in the FS series, which were all F8 and primarily designed for visual use (especially planetary and Lunar), the FS-60 is F5.9 (355mm F.L.) and aimed at the imaging market. Another difference is that the larger FS-series lenses all sit in sophisticated, collimatable cells, whilst FS-60 lens … err, doesn’t. Again, it is interesting to note that Borg’s small Optron lenses do have the same sort of proper cells and coatings that the larger Taks get.

On the first FS-60 I owned and originally reviewed - a 2009 model FS-60CB - the lens coatings were not as good as the larger FS models and looked suspiciously like ‘China’ green multi-coatings. The earlier 2006 FS-60C has proper broadband multi-coatings, but still not as good as other small Optron-made Taks and Borgs.

I started wondering if Tak were getting the FS-60 lens elsewhere and indeed whether it was fluorite or high-fluoride glass. So I did a laser test (on the 2006 FS-60C), As you can see above, there is no doubt: it’s fluorite!

Laser test on FS-60C objective clearly shows the laser disappear in the fluorite element (fluorite, unlike glass, doesn’t scatter a laser).

FS-60CB lens from 2009 – China Green coatings?

FS-60C lens from 2006 – quality multi-coatings.

FS-78 objective with very high quality multi-coatings and adjustable cell.

Fluorite, mating elements and chromatic aberration

A quick comment on chromatic aberration is in order. The FS-60 is widely known to be less than perfect in this respect and has a similar level of false colour to an F6 ED doublet like a TeleVue TV-60. On the face of it, this seems odd, because the FS-102 has much lower levels of chromatic aberration than the TV-102. Why should this be?

The answer, I suspect, comes down to the type of flint glass used in the negative lens of the doublet. Fluorite does not create a superior apochromat on its own, to do so it needs the right glass for the mating element. One of the reasons the F8 FS-series, Vixen FLs and the like were discontinued was that the glass for the mating element contained heavy metals and was proscribed in the move towards eco-glasses.

My guess (and it’s only that) is that the FS-60 uses a less ideal flint glass than its discontinued F8 cousins, preventing realisation of the full performance potential for the fluorite positive element. Another possibility is that the lens has a simpler design with little or no air gap. Borg fluorite doublets have a large air-gap which allows for better correction of various aberrations (see laser tests below), so that the F4.5 67FL has similar false colour to the F5.9 FS-60.

The Borg 90FL (like the 67FL) has a significant air gap between the elements; the FS-60 appears not to have.

Two Optron objectives: Borg 67FL and FS-60. Borg cell is larger, more sophisticated, more like larger Taks.

Tube

If the lens on the FS-60 looks similar to, but not quite the same as, as its larger siblings, then the same is also true of the rest of the OTA. The blue lens ring, oversized dew-shield and multiple knife-edge baffles that characterised the F8 members of the FS-series are all gone, as is the cast ‘manhole cover’ dew-cap that was an FS trademark.

The FS-60CB tube has no baffling, just flat-black paint, whilst FS-60C has a single baffle.

The FS-60 dew-shield is the same diameter as the tube, reminiscent of a Borg or a late Vixen FL. On the FS-60CB the dew-cap was low-rent black plastic but the older FS-60C has a Takahashi-green pressed steel item like recent Takahashis.

The OTA itself is very short (for back-focus and compactness) and will need extensions to come to focus in some cases. Two slightly different models exist, as I have said. The original FS-60C has a slightly longer tube than the later FS-60CB which was introduced to give more in-focus for imagers (to repeat myself, the 2006 model in the photos is an FS-60C; the 2009 model is an FS-60CB). You can convert an FS-60C into an FS-60CB just by buying a new barrel.

The standard visual back is 1.25”, but you can fit a 2” as an accessory. Doing so yields a staggeringly wide maximum field-of-view: 7.4° at 9x with a 40mm Pentax XW, almost identical to the latest Swarovski EL 8.5x42 binoculars, but with much more light gathering power.

Focuser

The rack-and-pinion focuser is reassuringly familiar: the usual Tak’ green enamelled casting, the familiar silver knobs and oversized tensioner. But unlike the larger FS models, the focuser on the FS-60 has a very short body for compactness, a bit like the one on the Sky-90, but with a smaller (~55mm) diameter drawtube. I’ll have much to say about the focuser in the test section: my FS-60C has a superb focuser; the FS-60CB I tested did not.

FS-60 focuser with optional 2” VB

Mounting

It goes without saying that the FS-60 is very compact and light-weight. Any small photo tripod would take it and it needs just the smallest counterweight on an equatorial.

Takahashi sell a tiny equatorial mount for the FS-60 – the Teegul Sky Patrol – ideal for eclipse chasers. The Teegul is marketed as a mount specifically for the FS-60 and it makes a surprisingly stable and solid platform for it. The Teegul/FS-60 rig can work in one of two modes: as a true German equatorial or as a half-fork. I’ll be posting a full review of the Teegul in due course, but here I’ll just say it makes an ideal grab and go setup when paired with the FS-60.

The FS-60 has a dedicated tube ring that is offset towards the objective end to allow better balance with a heavy camera (or eyepiece). The ring fits the standard Tak’ 2-hole pattern, but also has a central 1/4-20 thread for a photo tripod.

FS-60C on Teegul SP2 in German equatorial configuration.

FS-60C on Teegul SP2 in half-fork configuration.

The FS-60 is over-mounted on the P2-Z and extremely stable and vibration free as the result:

For this review, I also mounted the FS-60 atop my big scope to let the mount find targets and track them for some astrophotography.

Accessories

Like BMW, Takahashi really start fleecing you on the optional extras. A raft of tasty bits-and-bobs are available for the FS-60, including the CQ 1.7x module I mentioned, a flattener, a reducer, a version of the extender-Q, a camera rotator and more besides.

One of many accessories for the FS-60, the CQ 1.7 extender module turns it into a flat-field F10 super-APO.

Finder

In theory any Takahashi finder will bolt on, but the FS-60 is usually found with the excellent 6x30 unit. My second FS-60 happened to come with the rare 5x25 finder that I think suits it even better. Either finder has a wide field, sharp optics and lots of eye relief.

In Use – Daytime

It isn’t waterproof, but otherwise the FS-60 makes a great daytime scope – it is light weight, sharp and doesn’t generate too much false colour (though some is noticeable if viewing birds in silhouette at higher powers. Wide-field Tele Vue eyepieces, like Naglers, give wonderful daytime views that beat just about any spotting scope.

In Use – The Night Sky

The FS-60 is typical FS-series in many ways. Cool-down is very fast and benign and the views are very sharp and high-contrast. Optical quality is excellent and the FS-60 takes high magnifications easily. Focus snap is precise.

In comparison with the TV60, I think that the FS-60 might yield a tad more contrast, but also (and it’s odd, this) a bit more chromatic aberration as well. Certainly you couldn’t describe the FS-60 as ‘visually CA-free’ in the way the F8 versions are and I’ve discussed why in the ’optics’ section above. Chromatic aberration is not in any way a problem on most visual targets, but at 100x on a bright Moon you can see it as you focus in on the limb. Overall CA levels are very similar to the TV-76 and (curiously) the Borg 67FL which is both larger of aperture and radically fast at F4.5.

The focuser is very smooth and accurate, like most Takahashi’s, but on the 2009 FS-60CB there was a major problem: image-shift. The other Tak’ FS-series have minor image-shift; the Sky-90 I tested had a quite a lot; that FS-60CB had much too much. At high-power the image really jumped around when changing focus direction, enough to make finding perfect focus more difficult.

However, the 2006 FS-60C that I still own has an excellent focuser: buttery smooth and with minimal image shift: just how Tak’ focusers are supposed to be.

What’s going on? Is this just variation between samples? I don’t think so. You see, many FS-60s end up with big CCD cameras hanging off that compact focuser and I reckon after while it causes wear and play. This isn’t really a criticism: expecting a small focuser to handle several Kgs of CCD is asking a lot. But it would explain why the Taks I have seen with image-shift problems have been imaging models. Either way, check for image shift before buying used.

The Moon

I have always loved the view of the Moon through FS scopes. There is something about the contrast between the white Moon and absolutely black space, with very little unfocussed light, that makes the FS-series special. Perhaps it’s because fluorite scatters so little (back to that laser result again). Whatever the reason, the FS-60 is no exception. The Moon at 100x with the 3.5mm Nagler was spectacular for a small scope and reminded me why I like fine refractors. The Questar may have shown more detail due its larger aperture, but I thought the overall view was nicer in the Tak’.

Jupiter

If you imagine that a tiny, fast APO can’t do planets you’d be wrong. At 100x with a 3.5mm Nagler the FS-60 showed an impressively sharp and detailed view of Jupiter, with four belts, polar hoods and some cloud belt detail, plus the Great Red Spot. On the night, I thought it provided a view of Jupiter every bit as good as the nearby Zerodur Duplex Questar I also had on test, but did so much more quickly from a warm room.

Mars

Mars is a tough object for many refractors. Not only because is it often very small and its features low in contrast, but also because of its colour. Most short focal length doublets suffer spherochromatism and especially so at the red end of the spectrum. In other words their optical quality takes a dive at longer wavelengths. The FS-60 illustrates this point: excellent on other solar system objects, it gives an image of Mars that is a bit woolly and bloated, just like other F6 doublets do.

Deep Sky

The FS-60 is ideal for very large DSOs and I really enjoyed using it on the Andromeda Galaxy and the North American Nebula, neither of which fit in most scopes’ FOV.

Of course, it’s only a 60mm ‘scope, but the FS-60 pushes the limits. I managed to split the double-double (2.3”) without difficulty, Rigel too. Many DSOs – M13, the Dumbbell, M42, M56 – looked better than they had any right to in such a small aperture, with the superb contrast and perfect optics helping out.

Astrophotography

The FS-60 has the potential to take great images of extended objects. To give you an idea of what’s possible, there follows an unprocessed single APS-C DSLR frame of M31. One thing to notice is the field curvature: you would need a flattener for any serious astro-photography, even on this chip-size. The second image is full-frame and the curvature gets quite extreme in the corners.

M31 at 130s ISO 800, Nikon 5100 APS-C DSLR – single frame, unprocessed.

M42 30s at ISO 1250 with Canon EOS 5D full-frame DSLR (NOTE: this is slightly defocussed, I will replace it when I get the chance; it still shows the extreme field curvature).

The FS-60 has too short a focal length to be ideal for solar system imaging (which of course is where that CQ module comes in), but photos of the Moon taken with it have the same qualities that the view does: super sharp and high contrast. In the photo below that wide field enabled me to capture a close approach of the Moon and Jupiter.

The Moon and Jupiter (top left) with FS-60: super sharp and wide.

Summary

The FS-60 is another excellent Takahashi in most ways: tiny and light, yet well-made, razor sharp, with do-anything optics. It has modest false colour on most things and takes high powers well. However, though it is very sharp on-axis, it really needs a flattener for APS-C, let-alone full-frame.

But perhaps the best feature of the FS-60 is its unrivalled flexibility, thanks to the thoughtful native design and copious accessories. Unscrew the objective and plug in the CQ module and it’s a mini planetary scope. Attach the reducer and it’s a 250mm F4 telephoto lens. Swap in an FC-76C objective unit to create a highly-portable (cos it splits) 3” APO. According to a Japanese website, you can even attach both the FC-76 objective unit and the Q module to produce an F12 planet killer (I’d love to try that).

Am I just imagining it, or is there something about FS-fluorite lenses that gives images with contrast nothing else can quite match? And let’s face it, the FS-60 is cheap for a Takahashi (the next one up – the FC-76 - is over double the price).

The 2009 FS-60CB seemed to have suffered some cost cutting compared to the 2006 FS-60C that I owned second: too much image shift, poorer coatings, no baffle, a plastic dewcap and rougher castings. From what I can see the latest version is more like that original FS-60C, which is good news for buyers today.

If you get one like my second, the FS-60C is very highly recommended and is one of my all-time favourites, but it’s possible the focuser wears badly if subjected to big CCD cameras, so check for image shift if you’re buying used and expect to buy a flattener for imaging.

 

 

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