The new FC-76D is an updated version of the original FC-76 from 1980. The multi-coated fluorite rear lens and eco-glass front element provides maximum light transmission. The design takes advantage of the advances in high resolution digital imaging. The advanced design allowed the focal length to be reduced by 30mm 594mm at f/7.8.
The DS model features a 2.6” focuser for imaging with CCD cameras and DSLRs. A sliding dew shield is also included and a larger OD 90mm tube.
The FC-76DS model features the Sky-90 2.6” focuser to better hold imaging packages which include DSLR’s and CCD cameras with filter wheels. A dedicated and flattener as well as extender are available to further enhance the capabilities of the FC-76DS. The tube diameter is 90mm and includes a retractable lens shade.
The dedicated reducer changes the focal length to 417mm with a focal ratio of f/5.5 and an image circle of 36mm. While the dedicated flattener at f/7.8 and 594mm produces a 40mm flat circle.
The model DC uses identical optical components (same focuser as FS-60C) in a smaller and lighter tube with a fixed lens shade and weighs a little less than 4lbs. The DC is easily transported and easy to set up. The tube OD is 80mm and includes a fixed lens shade.
Both models are allow the user to use either for solar eclipse imaging. Both can be carried by the Teegul Sky Patrol III or larger PM-1.
FC-76DS
Design Doublet fluorite apochromat
Diameter ø76mm
Focal ratio f/7.5
Tube diameter ø90mm
Tube length 550mm
Weight 6.6lbs
FC-76DC
Design Doublet fluorite apochromat
Diameter ø76mm
Focal ratio f/7.5
Tube diameter ø80mm
Tube length 650mm
Weight 4lbs
FC-76DCU
The FC-76DCU model features a fixed dew shield and smaller, 80 mm
diameter barrel for the same performance in a package featuring reduced
weight and overall length. It utilizes a 1.25 inch rack and pinion
focuser.
Dedicated Reducer
Focal ratio f/5.5
Focal length 417mm
Image circle ø36mm
Dedicated Flattener
Focal ratio f/7.8
Focal length 594mm
Image circle ø40mm
Optical Tube Assembly only (mount, tripod, tube holder and finder sold separately).
FC-76DC Visual System Chart
FC-76DC Extender Q System Chart
FC-76DC Extender C2X System Chart
http://alpha-lyrae.co.uk/2017/03/12/takahashi-fc-76-dcu-review/
Takahashi FC-76 DCU Review
For many observers, there is something about a high quality
refractor that no other telescope design can quite match. Clearly I buy
into that line of thinking given the scopes that are displayed on the
“My Equipment” page of this website. I have even been known to state
(with tongue slightly in cheek) that “mirrors are for shaving.”
However, and this comes from experience, larger aperture models become
very unwieldy and difficult to mount, but at the smaller end of the
aperture spectrum, four inches and under, they represent perhaps the
best choice for grab and go scope and certainly as a travel scope to
supplement a larger scope that stays at home.
In the 21st century, ever increasing urbanisation and the
inevitable increase in light pollution that comes with it, means distant
travel is becoming a necessary evil to find truly dark skies. That can
mean international journeys and the restriction of airline baggage
allowance. While I am happy to leave a tripod and mount in my checked
luggage at the mercy of baggage-handlers, the fragile optical components
need to ride with me in the cabin which introduces fairly severe
restrictions on maximum dimensions and weight. Length of the OTA in
particular eliminates a large number of potential refractors given the
most generous airline cabin bag must be no more than 56cm long (22
inches). While my own APM TMB 105 triplet Apo (read the review here)
at only 19” long comfortably complies, the scope is rather heavy at
around 7kg with tube rings, finder and diagonal which means a more
robust mounting solution must be taken along, something that is not
always practical.
My annual trips to Africa which have very limited total baggage
weight limits due to small aircraft used for internal flights left me
looking for a high quality, light weight refractor for those times when a
Cessna or helicopter was part of my travel itinerary.
The FC-76 Objective Unit screws in place of the FS-60 lens cell assembly, creating the 3? f/7.5 FC-76.
The search initially led me to the Takahashi FS-60 (read the review of that scope here)
which is less than 30cm in length and weighs little more than 1.3kg
meaning I can always take optical aid on a trip, no matter how tight the
luggage restrictions are. As fantastic a performer as that scope is,
it is still only a 6cm (2.4”) aperture scope and can only do so much.
However, one feature that really appealed about the basic FS-60 is its
modular nature where a whole host of adaptors including extenders and
flatteners can be screwed in changing the optical parameters of the
system. The most exciting of which is the FC-76 Objective Unit which
screws in place of the FS-60 lens assembly, converting the scope into a
full 3” FC-76DC.
The Takahashi FC-76
Takahashi pioneered the use of artificially grown fluorite in telescope
lenses with a number of early models hitting the marketplace in in the
1970s. The original f/8 FC-76 model was launched in 1981 and was
discontinued many years later with the introduction of the FS series
which placed the positive fluorite element at the front in a more
traditional Fraunhofer configuration. More recently, Takahashi has
reintroduced the FC series in 76mm and 100mm models, though these new
versions have reduced the focal ratio to f/7.5.
The FC-76 is available in two models, the DS and DC. The DS model is
larger with a 95mm diameter optical tube, sliding dew shield as well as
a heavier duty 2.6” focuser from the Sky-90. The DS is 550mm long and
weighs 3.0kg (6.6lbs). The DC model is a lighter weight (1.8kg /
3.9lbs), narrow body version (80mm) of the same objective lens design,
coming with a smaller focuser that is also found on the FS-60. The dew
shield on this model is fixed which increases the OTA length to 650mm.
At 3kg the DS model is perhaps a little heavy to be called truly
portable under any condition, and the DC model is a little too long to
comply with international travel cabin baggage allowance. Fortunately,
there is a third choice which combines the best of both the DS and DC.
That is where the FC-76 Objective Unit comes in. The DC model shares
the same optical tube diameter as the FS-60 which means the lens cell
can simply be removed and the 76mm unit can be screwed in its place.
Now you are faced with a 76mm scope that weighs less than 2kg, and
thanks to the fact that it splits in two, no component is longer than
34cm resulting in compliance with the most restrictive of baggage
dimension allowances.
Though
I own the FS-60, each component required to create the FC-76 DCU is
available separately so you can own the split tube FC-76 without
purchasing the FS-60.
What if you do not want to pay for a FS-60 telescope as well?
Fortuitously, you can put this scope together yourself. To do so, you
would need a 2” Feathertouch focuser (I recommend the FTF2015BCR-LW) at
around £430, the Starlight Instruments Takahashi Adaptor (part number
A20-302) at £80, the FS-60CB tube (part number TSK06211) at £95, and the
FC-76DC objective upgrade (TFK07650) which costs £931. The total price
is around £1,500, compared to approximately £1,200 for the regular DC
model, though you are benefiting from an upgraded focuser in the form of
a Feathertouch and now have the advantage of a more portable scope.
The travel bag provided with the purchase of the FC-76 DCU when purchased in Japan. Source: takahashijapan.com
Takahashi themselves have now acknowledged the attractiveness of this
split tube arrangement, announcing the FC-76 DCU in December 2016 with
the components coming in a small travel bag. However, I have yet to see
any sign of this model on any western Takahashi dealer site so if this
seems attractive, you should speak with your local retailer.
The OTA
The first thing that strikes you about the FC-76 Objective Unit is
actually how well packed it is. Tripled boxed with polystyrene inserts,
plenty of bubble wrap and packing chips means there is no danger of the
scope not arriving in perfect condition. As soon as you liberate the
scope from the packaging, the quality is instant Takahashi. The OTA is
wonderfully finished with a deep, pearly white paint with silver accent
around the lens cell and capped with the classic “Takahashi Green” lens
cover.
Takahashi offer two clamshells with an internal diameter of 80mm that
can be used with the FC-76DC. The FS-60 clamshell is narrower with a
small foot which offsets the mounting position which helps with balance
of scope that can be slightly back heavy, despite its length, when using
a large 2” eyepiece. The larger clamshell is actually intended for the
FC-76DC but I find the smaller model more than capable and appreciate
the reduced weight when travelling. Should clamshells not be your
thing, the Borg (part number 7083) tube rings will also fit the scope.
The two 80mm inside diameter clamshells available for the FC-76 narrow body DC model.
The Lens
The FC-76 uses a doublet lens in a less common Steinheil arrangement
with the positive fluorite element at the rear and a negative eco-glass
element at the front. Amateur astronomers are known to fixate on the
type of ED-glass used in a refractor lens, and while many have
dispersive characteristics which come close to artificially grown
crystalline fluorite (in reality it is the mating element which
determines colour correction), for me at least, the most exciting
property of fluorite is the reputation for scattering less light than
any glass, a vital property for producing high contrast views which are
crucial in astronomical observation. Having used the FS-60 for a number
of years, the extreme contrast and low scatter demonstrated by that
scope has left me a bit of a believer that the reputation is deserved.
The lens of the FC-76. Even with a point blank flash from the camera, the lack of reflection and scatter is obvious.
The lens sits in a wonderfully machined, temperature compensating
cell, which is not much larger than the lens itself. To maintain the
narrow diameter of the scope, there are no collimation screws on the
76DC (the FC-76DS can be user collimated) though I would highlight that
over more than two years of use, I have removed the objective unit many
times, and it has not lost collimation upon reattachment, thanks to the
excellent machining and fine tolerance of the matching threads on the
objective unit and secondary tube. Unlike the original FC series of
scopes, all lens surfaces are fully multicoated and the quality of the
broadband ant-reflection coatings are first class, only revealing
themselves via slight reflections when a bright light shines directly on
them.
The optics can show some minor astigmatism during cool down but this
is completely absent once cooled and only seems to manifest when sudden
extremes of temperature are encountered such as moving from a warm house
out into a frigid winter night. Even then, patience does not need to
be a virtue as the scope cools in a matter minutes and will then perform
at its best.
The inside of both the Objective Unit and secondary tube are painted
flat black with a couple of knife-edge baffles which help to minimise
stray reflections from off-axis light rays.
If I have one criticism, it is the length of the dew shield beyond
the front lens surface. With the diameter of the main tube barely
larger than the lens itself, the lens cell actually sits inside the dew
shield meaning it only extends a couple of inches beyond the lens and on
particular damp nights, I have had some problems with the lens fogging
up earlier perhaps than I would had the shield been a bit longer.
Focuser
What more can be written about Starlight Instruments Feathertouch
focusers that has not been shared many times before? Almost universally
believed to be the finest focusers available, they are wonderfully
machined, precise and very strong. The lightweight model I use with
both my FS-60 and the FC-76 is the FTF2015BCR-LW which has a 1.5” long
drawtube. The lightweight model performs just as well as the regular
two inch feathertouch focuser (which I have on both of my 4” class APM
LZOS triplets) but weighs 0.278lbs less at 0.848lbs. I would also
highlight, that aesthetically at least, the silver skeleton cage of the
lightweight model is an excellent match for the silver accent around the
lens cell assembly of the FC-76.
The stock Takashashi focuser supplied with the FS-60 and FC-76 only has 1? of travel as seen here fully extended.
The standard equipment Takahashi focuser that comes with the FS-60
and FC-76DC is a single speed unit which is very smooth, but perhaps
lacks the absolute precision of a Feathertouch focuser. Natively, the
focuser will not accept 2” accessories though an adaptor is available.
However, the biggest weakness is the drawtube is only one inch in
length. The consequence of this is that a visual observer will find
themselves screwing in and removing adaptors as a means of course focus
with final fine adjustments coming from the focuser itself. As someone
who often finds themselves switching eyepieces rather frequently, this
can be a bit of pain. Barlow lenses which are not usually par-focal can
shift the focus point of an eyepiece considerably so consider a Tele
Vue Powermate or better yet, a Nagler Zoom for high power viewing. It
is worthy of note that there is some minor evidence of cost cutting as
the focus wheels are painted plastic as opposed to metal found on the
larger Tak focusers.
6×30 Finder
As the FC-76 is rather portable, it has accompanied me to many of the
monthly Baker Street Irregular star parties in central London. While
most attendees are more than happy for a quick peak at whatever
celestial delight the scope is currently pointed at, occasionally
someone comes along who is in the market for a small refractor and
starts asking plenty of questions. Almost always they know what the
scope is, and if it is a potential option, it usually means they are
relatively experienced astronomers (at its price point it is hardly an
entry level model). More often than not, at some point that questioning
turns to the cute little finder and whether it is “worth the money?” or
“surely a 50mm finder would be better?” That is when I tell them to
look through it.
The wonderful 6×30 Takahashi finder and bracket mounted on a 76mm tube-ring for attachment to the scope.
The almost ubiquitous 50mm finder seems to have been rapidly
declining in quality over the last few years. The images are dull, only
vaguely sharp in the middle of the field, while offering limited eye
relief. The 6x30mm (8o field) Takahashi finder is somewhat
of a minor legend because it has none of those qualities. The images
are bright and crisp across almost the entire field and it is delivered
with copious amounts of eye relief. Everyone who looks through it is
impressed and it certainly leaves them giving serious consideration to
spending the £130 asking price for the finder and bracket.
The build quality matches the high quality of the Takahashi line of
scopes with the same excellent optical coatings and wonderful deep white
paint finish. In my opinion it is the finest finder I have ever used.
However, if you have built your split tube FC-76 from scratch, or
just switched out the stock focuser of your FS-60 for a sublime
Feathertouch as I have, attaching the finder to the scope presents a bit
of a challenge. The finder bracket is easily attached to a mounting
plate located on the stock focuser, but no such provision exists on the
Feathertouch. Fortunately, there is a rather simple solution. The
bracket is attached a 76mn tube-ring which snuggly fits the outside
diameter of the focuser. This comfortably holds the finder in place and
can be adjusted by simply loosening and tightening the thumb screw on
the tube ring.
The 76mm tube-ring fits perfectly around the Feathertouch focuser.
Under the Night Sky
First light with the FC-76 came almost a year after I purchased both the
FS-60 and Objective Unit having somewhat fallen in love with the baby
Tak on a trip to Namibia. However more local dark skies beckoned and
not wanting to carry one of larger LZOS made triplets, the FC-76
suddenly seemed like the perfect choice. Those first views of some
showpiece DSOs of the Northern Hemisphere were impressive to say the
least.
The star test is among the very best I have seen. The Fresnel
diffraction pattern showing virtually perfect levels of spherical
correction, with a pale green rim outside of focus and a delicate
magenta hue inside.
The view in the eyepiece is the classic razor-sharp tiny jewels on
jet black cloth that no other telescope design seems to be able to quite
match. As with all quality telescopes, the image snaps to focus. At
f/7.5, the focal ratio is slightly longer than I am used to with all my
other refractors and the small increase in the depth of field is
welcome, requiring less frequent focusing due to atmospheric induced
focus issues. Inspection of the summer Milky Way star clouds with a
widefield eyepiece showed an image which is sharp over 90-95% of the
field with a slight defocusing due to field curvature at the very edge
of the field.
The FC-76 DCU set up for a night of stargazing at Astrocamp in the Brecon Beacons.
When it comes to refractors, questions inevitably turn to false
colour (personally I would be more worried about spherical aberration)
and here the FC-76 does exceptionally well. While it is not quite in
the same league as my LZOS triplets which are completely colour free,
the FC-76 shows no extraneous colour at all on all but the most
challenging of objects. I have been unable to detect any false colour
on the Moon or Jupiter even at magnifications approaching 200 times.
However, Venus and some particularly bright stars such as Sirius do show
some very minor colour fringing but I would highlight that I really had
to look for it and in no way detracts from the sharp, high contrast
views.
Many astronomers believe that a 4” scope is the minimum aperture
needed for serious planetary observing but I would offer the FC-76 as
evidence to the contrary. Just like its little brother, the FS-60, the
lack of scatter around bright planets and the limb of the moon is
remarkable, and this improved contrast really brings subtle planetary
detail into view. Jupiter shows a wealth of detail including several
bands, dark storms and incredibly a salmon pink colour (using the Baader
BBHS diagonal) in the GRS. I have heard it said that 6” in the minimum
aperture for colour to be seen in the GRS. Transits of the Galilean
moons and their shadows are easy.
Mars is the Achilles heel of the basic FS-60. Not so with the
FC-76. Though the recent opposition was not particularly favourable
from the UK, at times of good seeing I was rather surprised by just how
many surface features I was able to see. Saturn is similarly impressive
with the subtle banding immediately obvious.
While I am not a huge fan of lunar observation, the views are
outstanding. Shadows are jet black, and the whites are as pure as
snow. The lack of scatter really reveals itself on the limb where the
sky is pure black. On bright objects like the moon, the ability to
really take the magnification up demonstrates the quality of the lens.
Even using the 2mm setting on my 2-4mm Nagler Zoom for 285x reveals a
super sharp image, even if the view reveals no additional detail and the
exit pupil is risking floaters in the observer’s eye ruining the view.
All the usual suspects in the double star world are easy quarry for
the FC-76, such as Castor, the Double-Double and Polaris (usually
considered a decent test for a 3” scope), more often than not at
relatively low magnification. That performance is hardly surprising
given the quality of the star test and sharpness of the image seen in
the eyepiece. In an effort to discover just what this scope is capable
of, I have run the gauntlet of increasingly challenging doubles, and the
FC-76 has left me more than impressed. Propus in Gemini is listed in
Burnham’s as a challenge for a 12” scope (that is perhaps a bit
pessimistic and might be more reflective of the general quality of
telescope objectives when published though the components were also
slightly tighter at the time of writing). I have certainly seen 8”
scopes fail to show the fainter secondary on nights of less than perfect
seeing. In my attempt to split this double (1.6” separation /
magnitude 3.29 & 6.15) I actually removed the diagonal and used
straight through viewing (not friendly on the neck) to reduce the
already low scatter still further and keep optical components in the
light path to a minimum. On one night of exceptional seeing, I was able
to glimpse the tiny secondary at 190x (3mm setting of Nagler Zoom),
like a small pimple on the edge of the bright primary. That is an
exceptional result.
The E and F components of the Trapezium in M42 can be tricky for a
scope of even quite large aperture when seeing conditions are poor.
However, it can be an excellent test of optical quality in small scopes
(4” class and under) when seeing is very good. A small scope with more
than a modest amount of spherical aberration will reduce contrast and
slightly smear the image rendering those elusive fainter components of
the most famous multiple star system invisible against the bright nebula
that cradles them. Using the 4mm setting of my Nagler Zoom (143x), I
have been able to pull E consistently and F intermittently on nights of
good seeing, providing further evidence of what the star test showed,
that my FC-76 has exceptional optics. It is certainly the smallest
scope I have used that has achieved this, though I am not alone in this
feat with a couple of other owners of 3” class scopes reporting success
online. However there are many, many more reports of similar aperture,
and larger scopes, failing to achieve this.
Combined
with suitable solar observing safety equipment such as the Baader
Herschel Wedge seen here, the FC-76 is a very capable instrument for
studying our nearest star.
When it comes to deep sky I would suggest that the scope punches
above its weight, especially from a dark sky site, thanks to the
exceptional sharpness and contrast of the views provided. My experience
with the FC-76 has led me to conclude that it matches lower quality
scopes that boast an inch or more of additional aperture in the detail
that can been seen even if the image itself is a touch darker than those
larger scopes thanks to excellent contrast. During the autumn 2016
Astro Camp, one of the organisers came up to me on the observing field
for a chat when I was pointing the scope at M13 in Hercules. Being a
silver rated International Dark Sky Association reserve, it was rather
dark which meant it was quite difficult to identify what scope I was
observing with. I offered a look and he was immediately impressed with
the image seen, saying the cluster was resolving nicely towards the
core. I retorted that it was “not bad for a 3-inch scope” which
immediately generated a “that’s only a 3-inch?!” response followed by an
immediate return to the eyepiece for another look. The next statement
summed up my opinion of this remarkable little scope. “That is a very
sharp image, those optics are very good.” Agreeing, I then slewed the
scope to the Double Cluster in Perseus which generated a similar
positive response. Such an assessment from another experienced
astronomer only further reinforces the conclusion that I have reached
over the last couple of years of ownership.
Another FC-76
It should be clear by this stage of the review that I am rather
impressed with the quality of the FC-76 but one exceptional model is no
guarantee (despite Takahashi’s reputation) that all examples are of a
similarly high standard. While only one additional scope is not a
sample set to draw any definitive conclusions, I was fortunate enough to
spend some time with another astronomer’s FC-76DS under the dark skies
of the Brecon Beacons and found the view through his scope to be equally
as impressive. While we did not test the scope rigorously, it was
clear from the views presented that this scope was of a similarly high
quality to my own FC-76.
Travelling with the FC-76
With no component of the telescope more than 13.5” in length, it is
possible to pack this down into a bag which will comply with the most
restrictive of cabin baggage allowances. I use the Think Tank Photo
Airport Essentials backpack (you can read the review of the Essentials Backpack here)
which is so small that it actually fits under the seat in front of you a
plane, should the need arise. The accompanying photograph shows how
much equipment I am packing for my summer 2017 trip to Vamizi island off
the cost of Mozambique.
The FC-76 and all required accessories along with plenty of camera equipment fit in the Think Tank Photo camera bag.
To keep weight down I use a 1.25” diagonal (with extension tube) and take three eyepieces, a 24mm Panoptic (24x/2.7o field), a 7mm Nagler Type 6 (81x/0.98o) and a 3-6mm Nagler Zoom (95x-190x/0.51o-0.26o).
All three eyepieces are high quality and provide me the max field of
view possible from a 1.25” EP through to very usable magnifications for
planetary and double star work.
Takahashi FC-76 DCU + EX-CQ
Google translating some Japanese websites suggests the 1.7x CQ module
that converts the FS-60 into the f/10 quadruplet FS-60Q can also be used
with the FC-76 objective unit to create an f/12.6 quadruplet. This is
perhaps a little surprising as I was under the impression that the CQ
unit was specifically designed for the FS-60. However, confirmation
that this could be done came in May 2016 when Takahashi produced a
limited run of 30 FC-76 DCU + EX-CQ packages which included the
Objective Unit, the Focuser Unit and CQ Module all in a travel bag.
Using the slightly unsafe method of Google translate on Japanese
websites (it translates Fluorite as Flow-Light thanks to phonetic
translation) reveals a claim that use of the CQ module improves the
polychromatic strehl ratio to almost 0.95, an incredibly high value for
any telescope. I do own the CQ module, but have yet to try this but
certainly will soon.
This
will be exciting to try! The FC-76 objective unit, the 1.7x CQ module
and focusing unit. Combined they create a 3? f/12.6 scope.
Conclusion
The Takahashi FC-76 lens is exceptional. The lack of scatter, extreme
contrast and excellent sharpness allow it to perform at levels above
what would be expected of a 3” telescope. All of the FC-76 models are
portable, quick to deliver maximum performance when taken outside from a
warm house, and can take high levels of magnification allowing them to
deliver on planets and double star work.
Would I recommend this scope to a beginner? No, certainly not. It
is expensive and you would get a lot more bang for your buck with a 6 or
8” Newtonian. But if you are an experienced astronomer looking for an
ultra-portable scope to take away to distant lands with dark skies and
you demand optics that are among the very best available, the FC-76
Objective Unit is highly recommended, either to those who already own
the baby Tak (FS-60) or to those who are prepared to construct it
themselves (hopefully Takahashi bring the FC-76 DCU to the West so you
won’t have to) as mentioned earlier in the review.
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