Takahashi FC-76DS 3-inch doublet refractor
Aperture: 75mm, 3 inches
Focal Length: 570mm, f/7.5
Supplier: Green Witch
Telephone: 01767 677025
Takahashi has a worldwide reputation for the quality of its refractors so its latest, the FC-76DS, has a lot to live up to.
This 3-inch apochromatic refractor has a doublet objective lens: the rear element is made of fluorite while the front one is made of ‘eco- friendly’ glass – in other words, glass that is lead and arsenic free.
These elements are multicoated, which helps to cut down on internal reflections and improves light transmission.
Though it has one lens element less, it can be considered as an update to the company’s much-revered FCT-76 triplet refractor of the 1980s.
There are several variants in the FC-76 family: the one we review here, the FC-76DS, features a retractable dew shield and has a focal length of 570mm, giving a focal ratio of f/7.5.
The tube itself is 567mm long with the dew shield retracted and 95mm in diameter, making it quite compact.
We found the dew shield did a very good job on all our observing and astrophotography runs, several of which lasted for up to four hours at a time.
The scope is fitted with Takahashi’s 2.6-inch Sky-90 focuser which, although it is single speed and lacks fine focusing, was very smooth with no slippage even when carrying heavy equipment.
Attached to it is an extender that can take 2-inch eyepieces for straight-through visual use. An adaptor for 1.25-inch eyepieces is also included.
The way the eyepieces are held in place depends on their size: 1.25-inch eyepieces (and camera nosepieces) are secured by a clamp that tightens uniformly around the barrel – we found it gave excellent grip – while 2-inch eyepieces are held in place using a more traditional pair of screws.
You get what you pay for
For visual observing we removed the main extender and fitted a star diagonal.
Centring the bright star Arcturus in Boötes in our 1.25-inch 26mm eyepiece, we noted that the image was very good in the central 90 per cent of the field of view, with star quality trailing off only slightly at the edges.
Through the same eyepiece, we found that Brocchi’s Cluster in Vulpecula fitted nicely into the field of view, which we estimated to be about 2.5º across.
We also used our 1.25-inch 9mm eyepiece and 3x Barlow lens to split double star Porrima in Virgo nicely; its component stars are currently separated by around 2 arcseconds.
Our 1.25-inch 26mm eyepiece gave a modest magnification of 21x.
However, the quality of the FC-76DS’s optics allowed us to push the magnification using both 2x and 3x Barlow lenses along with our 9mm and 26mm eyepieces.
These combinations still gave us good views of the brighter Messier galaxies, such as M81 and M82 in Ursa Major, and M65 and M66 in Leo, along with the Ring Nebula in Lyra and the Dumbbell Nebula in Vulpecula.
Our most memorable deep-sky view came when we turned to globular cluster M13 in Hercules.
It was impressive as we cranked up the magnification and it became a tight ball of stars just resolved into pinpricks.
We spotted the dark ‘propeller’ feature and with careful scrutiny we also found nearby 12th-magnitude galaxy NGC 6207.
Back in our Solar System, the planets were understandably quite small, but again on pushing the magnification we were rewarded with respectable views of Jupiter with bands and its four Galilean moons.
Turning to Saturn, the rings and a planetary belt were evident, along with three of its moons as well.
Our own Moon still held enough detail under high magnification to satisfy our curiosity – all in all this is a capable instrument.
Our astrophotography tests showed some slight distortion close to the image edges, but the overall results were pleasing.
Although we reviewed the basic optical tube here, the FC-76DS can also be bought as a package that includes a clamshell tube holder, a 6x30mm finderscope and a bracket for £2,487.
Takahashi equipment doesn’t come cheap but it’s hard not to appreciate the quality of engineering, the lightweight construction and its versatility as both a visual and an imaging instrument.
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This review appeared in the July 2013 issue of BBC Sky at Night Magazine