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Takahashi FC-100 Classic (‘F’ Lens Version)

I recently reviewed Takahashi’s latest 100mm apochromat, the FC-100DZ that brings back an F8 Steinheil with superlative correction, including for high-power visual use. It got me wondering about its illustrious forebear, the classic FC-100 from the 1980s, a scope that’s loved by many in-the-know Takophiles, including Ed Ting.

Then, as luck would have it, a rare late example came up for sale and I grabbed it with a view to this review, but also to compare it with the new version and see what thirty years of optical technology (and a ban on flint glass containing heavy metals) have done for a famous design.

At A Glance

Telescope

Takahashi FC-100

Lens Design

Steinheil fluorite doublet

Aperture

100mm

Focal Length

800mm

Focal Ratio

F8

Tube Diameter

114mm

Length

800mm (31.5”) w/o visual back

Weight

4.2Kg (w/o ring and finder)

Data from Me.

Design and Build

This scope, Takahashi’s original and classic FC-100, was introduced back in 1981, long before the digital imaging revolution that led to the rebooted FC-100D. Even so, its appearance and features have similarities with Takahashis from every decade since.

At the time, the FC-100 was part of a range of F8 fluorite doublets, from the diminutive FC-50, through the FC-60, FC-76 and culminating with the FC-125. The FS-range that superceded it changed the line-up slightly, swapping the F8 FC-60 with the hugely popular F6 FS-60 and adding a top-of-the-range 6” F8 fluorite doublet, the FS-152 (I almost bought the last new one in the U.S., but that’s a story for another time).

Note that an FC-150 doublet was never offered. Instead, Tak’ made an FCT-150 – an F7 triplet that was fabulously expensive back at a time when a 6” fluorite blank for the centre element cost $$$Big. In fact, that FCT-150 was the top of a parallel range of rare and desirable triplet imaging refractors that included an FCT-100 introduced in 1984. The FCT-100 looks much like the FC-100, but has a bigger focuser and a focal length of just 640mm.

The FC-range were all designed for excellent visual performance (especially for the Moon, planets and double stars), but for 35mm emulsion imaging with a flattener too.

The FC-100 has developed a reputation for being one of the finest Takahashis for contrast and high-power sharpness and some (perhaps unfairly) regard it as superior to the FS-102 that superceded it.

This particular FC-100 dates from the early 1990s – the last few years of production.

Various different versions were available over the years, including one that replaced the standard 2.7” focuser with a heavy-duty item for imaging. However, unlike the FS-102, I can’t find evidence of a sliding dew-shield version of the FC-100 (but as always, reach out if you know better!)

1980s FC-100 catalogue entry (image credit Takashashi).

The FC-100 and FC-50 were once part of a whole range of Takahashi F8 Steinheil doublets.

Decals are classic 1980s Takahashi, but early examples would have had grey detailing, like the FC-50 above.

Early 1990s FC-100 reviewed here, alongside 2020 FC-100DZ – both are 100mm F8 Steinheil fluorite doublets.

Optics

Both the original FC-100 and the FS-102 that followed it from the early 1990s were ~F8 air-spaced fluorite doublets (made by Optron in Japan as always). However, though the FS-102 has its fluorite crown element at the front, making it a Fraunhofer type doublet (like most refractors), the FC-100 is a Steinheil doublet with the fluorite positive convex element at the back. Takahashi have reverted to this lens type for their recent FC-100D and FC-76D models.

Takahashi adopted the Steinheil design because fluorite couldn’t be coated at the time and was vulnerable (fluorite is soft and may deteriorate), so putting it at the back, out of the way of lens wipes and dew, made sense.

That fluorite crown was partnered with a flint containing heavy metals that wouldn’t be used for environmental reasons today, but allowed excellent correction for a doublet – one of the reasons the original FC-100 has such a strong reputation.

A key point here is that most FC-100 Classics have an uncoated fluorite element at the back, which means they transmit a bit less light than later models. However, the FC-100 pictured dates from the last years of production, when some lenses with fully coated fluorite were fitted. These later lenses have a red capital ‘F’ engraved in the lens ring.

Coatings are an older type with a reddish-purple hue, but transparency is very good even by modern standards – see comparison with a 2020 FC-100DZ below. It’s interesting to note that my AP 130 EDT, made around the same time, has only single coatings.

The FS-102 that replaced the original FC-100 has a focal length of 820mm (F8.1), making it slightly slower than the FC-100 which has a focal length of exactly 800mm, same as the recently introduced FC-100DZ (confusingly, of the other recent FC-100s, the DC and DF are both F7.4, whilst the DL is F9).

Unlike the rebooted FC-100D, this original FC-100 has a ‘proper’ lens cell, attached with three pairs of push-pull screws to allow collimation. Whether this is ‘better’ than the integrated, non-collimatable cell in the FC-100D I can’t say, but it does cool down very rapidly and benignly. Oddly, only the FC-60 had a non-collimatable objective, the rest of the range (FC-50 included) had a ‘proper’ lens cell like this FC-100.

Original cast dew-cap with solar port.

That red ‘F’ denotes a coated fluorite element and modern performance.

Takahashi FC-100 classic (right) with FMC ‘F’ lens compared with latest FC-100DZ (left).

Tube

(Note: I’ll go into some detail on finishes as they vary and can be confusing when searching for a used example. You can read more about Takahashi colours and finishes here.)

The OTA has a large (for a 4” refractor), fully baffled tube, 114mm in diameter, with a fixed dew-shield. As usual, both focuser and lens ring thread on, held tight with tiny Allen grub screws.

In this case, the tube is finished in the usual off-white enamel, the focuser and lens ring in the knobbly lime green powder coating that has only recently been superceded by a bluer shade. Earlier FC-100s may have a glossier grey enamel finish to the focuser and lens ring, seen on the FC-50 above.

The tube looks very similar to the later (only by a few years in this case) FS-102, apart from the different dew-shield stickers. Later FS-102s were distinguishable by a gloss blue lens ring, but earlier ones had the same lime green lens ring as the FC-100.

However, the FC-100 is actually significantly shorter than the FS-102 and a little lighter too – the FC-100 seems like a smaller and more handy scope than its replacement model.

Internally, the tube features Takahashi’s usual multiple knife-edge baffles for minimum stray light and maximum contrast.

The large dewshield is closed by a cast cap that looks a bit like a small green manhole cover. It slides into the dewshield on felt and has a 50mm threaded solar viewing port. It’s a heavy thing, but functionally the best I’ve ever used. Modern Takahashis have press-over tin dew caps that are harder to get on and off and much less classy and distinctive.

FC-100 (top), FS-102 (bottom) share tube sizes and focuser, but FC-100 is shorter.

Focuser

The FC-100 uses the 2.7” focuser that featured on many Takahashis of the era, up to and including the FS-128. Despite being only single speed, it has loads of travel, is smooth and stable and copes well with heavy loads like CCD cameras and binoviewers. Astro Physics’ competing 2.7” focuser from the same era boasts CNC construction, but is functionally no better in my opinion, if anything slightly less smooth.

The silver knob on top is the lock screw and has an excellent action. Again, it’s progressive and effective but avoids much image shift. When new (and then if looked after), these focusers have very little image shift in general, but if abused or tampered with image shift can be a problem – caveat emptor when buying used.

The large drawtube was designed to avoid vignetting on a medium-format emulsion camera and so works well with CCDs that have larger sensors and full-frame DSLRs.

The focuser has Takahashi’s signature cast and silver-anodised focuser wheels. On cheaper models, such as the FC-60 of this era, those knobs could be plastic imitations, but on the FC-100 they should always be the real thing.

The standard visual back in those days was a 1.25” that has Takahashi’s signature silver-ringed twist-lock and threaded into a heavy cast and green-coated adapter to the M72 draw-tube thread. The FC-100 would originally have shipped with several short, threaded extension tubes for straight-through viewing.

A 2” visual back was originally available as an optional extra and M72 adapter rings can still be obtained today to fit a generic 2” visual back (often called an ‘eyepiece holder’). For example, Borg currently make an M72-M57 adapter and several sizes of M57 eyepiece holder to fit.

Takahashi 2.7” cast focuser was fitted to many of their scopes: it is smooth, stable and has lots of travel.

CNC 2.7” Astro Physics focuser from the same era is no better than the cast-bodied Tak’.

Mounting

Like other Takahashis up to this size, the FC-100 has a cast clamshell-style ring with a dual hinge, a heavy chromed clamp knob and thick (green) protective felt. The clamshell is equipped with a pair of holes for M8 bolts at 35mm spacing for direct fitment to Takahashi mounts.

3rd party dovetail plates are available to fit this hole spacing, but for fitment to a Vixen-style dovetail (also Sky-Watcher etc), Takahashi make a slim silver dovetail (intended for the Mewlon 210) that has the same chamfer.

The FC-100 is quite large for a 4” refractor, but it’s notably lighter and shorter than the FS-102 that followed it and so a bit easier to mount. Small to medium German equatorial mounts should support it fine; my Vixen SX2 needs only its lightest counterweight and is very stable with the FC-100.

For quick looks with an altaz mount (something the FC-100 works well for, due its rapid cooldown), you would potentially need something larger than a Vixen Porta or SW AZ-4 for stability at high powers.

FC-100 OTA with clamshell ring and 1.25” visual back.

Accessories

The complete package would have shipped with the clamshell ring and 7x50 finder as standard, but you could have bought a bare OTA and then a smaller finder – 5x25 or 6x30. All three finder types are excellent; but with the optional illuminator, the 7x50 makes finding things a doddle: it boasts an illuminated reticle with a central gap for the target, good eye relief, super-sharp optics and a wide flat field.

Other accessories would have included a camera rotator and reducer/flattener that shortened the FC-100’s focal length to an ambitious F5.9.

Illuminated 7x50 finder was standard.

6.3° FOV of the 7x50 Takahashi finder – flat and sharp.

In Use – Daytime

Viewing silhouetted branches at 100x gave a very sharp view with only the faintest traces of false colour either side of focus and very little in focus. For comparison, the latest FC-100DZ showed no false colour at all, whereas a TV-85 generated a light wash of green and purple either side of focus at the same power and with the same type of eyepiece (a Tele Vue Nagler Type 6).

One big difference compared with a modern doublet is evenness of illumination and you can see this on telephoto images taken with the FC-100 during the day. Centre field sharpness and false colour correction are excellent, but brightness varies off-axis in a way you don’t get with an FC-100D. I’ve seen this effect in other older Optron lenses, such as the Vixen FL80’s.

Prime focus daytime shots are sharp but illumination is uneven, typical of older doublets.

100% crop shows low level of false colour.

In Use – Astrophotography

Daytime telephoto images are noticeably inferior to a modern FC-100D in terms of even illumination, but for imaging (at least on smaller sensors) the FC-100 Classic produces serviceable subs even without a reducer.

Like most quality apochromats, the FC-100 produces excellent prime-focus images of the Moon that are sharp from limb to limb.

Flatness across APS-C sized crop is quite good.

In Use – Observing the Night Sky

General Observing Notes

The cast manhole cover dewcap remains the best ever. It slides in and out with perfect friction – easy to remove and put back (in the dark, when you’re cold and tired) - but never just falls out. I much prefer it to the press-over tin on modern Tak’s, honestly to Tele Vue’s screechy screw-caps too.

The FC-100 is just a pleasure to use: it’s ready to use after a few minutes, shows brilliant, pinpoint star images across the field.

The focuser just works, even with heavy diagonals and eyepieces, even after thirty years of regular use. It has little image shift and no tendency to rack out on its own. The lock knob on top is progressive, effective and again free from image shift.

I appreciate the Steinheil lens for a scope that gets used a lot, just because I worry less about the lens getting dewed up (it’s fronted by hard flint glass, not a fragile fluorite or ED crown).

Cool Down

In keeping with its thin lens elements and proper cell, the FC-100 is fast-cooling for a 4” refractor, ready within 15-20 minutes.

Star Test

The star test appears excellent with evenly illuminated similar diffraction rings either side of focus and a very tight and dim diffraction ring and dazzlingly small Airy disk in focus.

The Moon

The FC-100 gives outstanding lunar views. Think Tele Vue, think the deep sky; but think classic Tak’, think Moon and planets. Minimal false colour means that terminator shadows are intense black against brilliant white, ditto the bright limb against dark space, with minimal scattered light and no violet wash of false colour to reduce contrast.

I’ve mentioned this before, but one test of a good lunar scope is viewing lunar mountains etched against black space on the Moon’s very edge and Tak’ doublets do this especially well, with minimal scatter and false colour fringe to interfere.

Highlights of a ten-day gibbous Moon included the rugged hills of the Montes Carpatus north of crater Copernicus, picked out in long-shadowed dawn relief. Near the southern limb, prominent craters Clavius, Longomontanus and deep Moretus with its tall central peak near the very edge of the Moon, really caught my attention. Further north, I found multiple craterlets in Plato (students at his Athenian academy, perhaps) and followed wrinkled ridges around mathematicians Euler and Lambert in Mare Imbrium.

Mars

Takahashi F8 fluorite doublets always seem to work well on Mars because they are well corrected into the red (whereas some ED doublets just aren’t) and the FC-100 is no exception.

At 13” in size, well after the 2020 October opposition, Mars at 267x with the 3mm setting of a Nagler Zoom was clear and sharp, though in some ways I preferred the view with a 4mm Zeiss Abbe Ortho giving 200x.

In both cases, Syrtis Major was clearly visible and the gibbous disk rendered crisp and with no false colour in or out of focus. Overall, the view was indistinguishable from the FC-100DZ alongside, with both scopes delivering a sharp view, snappy focus at 267x and complete freedom from chromatic aberration.

Both fluorite scopes gave better views that the two ED glass doublets I had to hand (Sky-Watcher’s 120ED and Tele Vue’s TV-85), both of which sloughed off red flare into the seeing and gave a slightly mushy view with lower contrast and less snappy focus.

Deep Sky

Views of deep sky objects with a Panoptic 19mm (an excellent deep sky eyepiece giving a moderate magnification of 42x and a nicely wide, flat field of view) were outstanding with dazzlingly brilliant and strongly (natural) coloured brighter stars, peerless contrast and a very flat field.

I had spectacular views of all my favourite early-winter DSOs: diamonds-in-mist Pleaides; the string of open clusters large and small in Auriga; smaller planetary nebulae like the Dumbbell, Ring and Crab; globular clusters - M15 in Pegasus, M13 in Hercules - that start to resolve nicely at this aperture.

The outstanding contrast makes low-power surfing of the Milky way especially pleasurable – a feast of star dust and clusters. The FC-100’s compact size and light weight mean it’s safe to loosen the mount clamps and just pan it by hand.

Overall deep sky performance was very similar to a modern 100mm (such as the FC-100DZ I tested alongside) thanks to that fully coated ‘F’ lens. Older models with an uncoated fluorite element are likely to perform less well for deep sky.

Takahashi doublets have a reputation for resolving double stars, due again to their high contrast and pinpoint stars. The Double Double in Lyra showed an excellent split, one of the best I’ve seen in a 4” scope: initially at 114x with a 7mm Tak’ Ortho, then at 200x with the 4mm setting on a Nagler Zoom yielding a big dark gap between the components of both stars. Likewise, Rigel was a very easy split with the fainter companion floating free of the dazzling main star.

Summary

A classic Takahashi fluorite doublet notable for its beautiful-but-simple build quality, ease of use and all-round excellence. The FC-100 gave just wonderful views of everything I set it on, from Mars, to the Moon and deep sky too. Light, fast cooling and trouble free, it’s a mid-sized refractor that works really well for quick looks as well as longer observing sessions.

Whilst I didn’t have an FS-102 for comparison, I suspect performance of this fully-coated ‘F’ lens version of the FC-100 is very similar, whilst it is usefully shorter, lighter weight and likely to stand up better to regular dewing thanks to having its flint element up front.

Meanwhile, the FC-100 gives very little away to the new FC-100DZ for visual use – just that very last trace of chromatic aberration.

The FC-100’s older lens design does, however, give a less evenly illuminated field for imaging and you might be better off with an FC-100D if imaging is your main use (unless you can find one of the premium 0.7x reducers originally sold as an accessory).

The classic FC-100 deserves its reputation for excellence, especially in this late version with a coated fluorite element. It’s a classic that makes few compromises. Highly recommended.

 

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