FS-60CB 2.4" F/5.9 fluorite doublet apo

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Takahashi fluorite lens
Apochromatic means “free from spurious color” – a refractor system without the faint violet halos of out-of-focus light you see around the planets, the limb of the Moon, and all the bright stars in an ordinary achromatic (crown and flint glass) refractor. All Takahashi fluorite doublet optical tubes are true apochromatic optical systems, with virtually perfect color correction.

Takahashi has been the acknowledged leader in ultra-premium apochromatic fluorite optics ever since they produced the first commercial fluorite refractor in 1979. That system moved Takahashi to a position of industry leadership in terms of optical quality, and Takahashi has never looked back since moving to the head of the class.

The Takahashi two-element air-spaced objective lenses use a full aperture laboratory-grown calcium fluorite crystal lens element, combined with a high refractive index flint-type glass element. This yields very high color fidelity and vanishingly low levels of spurious color. Laboratory-grown fluorite crystals are used, rather than naturally-occurring crystals, due to the lab-grown variety’s optical uniformity, clarity, freedom from striae and internal stresses, freedom from being adversely affected by dew and moisture (as early natural-crystal fluorite lenses could be), and their ability to be hard multicoated in a vacuum chamber for high light transmission.

The Takahashi color correction equals, or exceeds, that of most triplet lens systems regardless of cost or brand name. Contrast is generally superior to triplet systems or doublet systems that use a low-dispersion crown glass element instead of fluorite crystal.

Since the Takahashi two-element air-spaced designs have fewer light-absorbing lenses than triplet systems, they generally have less glass to absorb light, therefore yielding brighter images than most triplets. All optics are fully ion-deposited hard multicoated (including the fluorite element) for maximum light transmission and contrast. Maintenance is less than oil-spaced designs, since there is no oil to potentially leak or become cloudy with age. In addition, Takahashi lens cells are fully collimatable for peak optical performance by using a simple optional Cheshire-type collimating eyepiece and the locking collimating screws on the lens cell.

The diagram below shows the differences in color correction between a conventional BK7 optical glass lens (shown in red), an ED glass lens (in blue), and a lens of calcium fluorite crystal (in green). The smaller the departure from the ideal focus, shown by the vertical line labeled “0”, the lower the amount of chromatic aberration and the better the correction for the specific color shown at the left of the diagram. You’ll note that the green line of the fluorite lens shows much less chromatic aberration across the entire visible spectrum than either of the other two glass types.

This compact Takahashi refractor optical tube makes an ideal eclipse scope and a super travel and backyard scope for spur-of-the-moment observing. It uses a 60mm f/5.9 fast focal ratio air-spaced doublet optical system. The front element is a laboratory-grown calcium fluorite crystal lens with hard multicoatings for maximum light transmission. The rear element is hard multicoated low dispersion flint glass. The combination of fluorite crystal and low dispersion glass provide absolutely superb apochromatic color correction that is visibly better than any ED glass doublet scope. Color correction is on a par with far more costly triplet systems, but the light transmission is higher than any triplet apochromatic system, due to the smaller number of optical elements to scatter and absorb light. This Takahashi optical tube uses a series of internal knife-edge baffles to block stray off-axis light for the highest possible image contrast. For more details, click on the “Takahashi fluorite lens” icon above.

Experienced observers sometimes report that the scope’s high contrast/diffraction-limited optics can be used at magnifications of over 100x per inch of aperture on suitably bright objects (the Moon and planets) on nights of exceptional seeing. Of course, we can’t guarantee you’ll be able to reach this kind of magnification level with any sort of regularity with this Takahashi (it would take the equivalent of a 1.5mm eyepiece and would produce a very dim 0.25mm exit pupil), but the possibility of very high magnification is there.

The smooth Takahashi rack and pinion focuser has large ribbed focusing knobs that are easy to grip and operate in cold weather, even when wearing gloves. The optical tube has a flat boss above the focusing knobs, with two mounting bolts to hold an optional finderscope, such as the straight-through Takahashi 5 x 25mm with its very wide 9° field. The supplied 1.25” eyepiece holder uses a non-marring nylon split compression ring system to hold your star diagonal or eyepiece in place. This system won’t scratch the barrel of your eyepiece or star diagonal, as an ordinary brass or steel thumbscrew can. A simple twist of the ribbed ring at the end of the focuser drawtube tightens the internal compression ring to hold your diagonal firmly in place; while a twist in the opposite direction lets you remove it with ease.

The Takahashi optical tube itself weighs less than three lbs. It measures only 17” long with dew shield in place. The optical tube is 80mm in diameter and an optional tube holder is available to fit the scope on a Takahashi mount (such as the altazimuth #TGS01 or the very compact #TGUL Teegul Sky Patrol equatorial).

The 60mm Takahashi FS-60C. Expensive for a 60mm optical tube? Yes. Worth it? Emphatically yes.

Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.95 arc seconds
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
The weight of this product.
2.9 lbs.
Heaviest Single Component:
The weight of the heaviest component in this package.
2.9 lbs.
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Planetary Observation:
Very Good
Binary and Star Cluster Observation:
Very Good
Galaxy and Nebula Observation:
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Planetary Photography:
Star Cluster / Nebula / Galaxy Photography:
5 years
Reviews from Cloudy Nights (www.cloudynights.com)
These reviews have been written by astronomers just like you and posted on the Cloudy Nights astronomy forums . . .
Takahshi FS-60C f/5.9 APO Refractor

User Ratings/Reviews from our Customers (www.astronomics.com)
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General Accessories
Tube Rings (1)
Tube holder for FS-60C
by Takahashi
Visual Accessories
Barlow Lenses (1)
2X 1.25" Barlow with compression ring
by Takahashi
Eyepieces (3)
5mm 1.25" long eye relief ED
by Takahashi
12.5mm 1.25" long eye relief
by Takahashi
18mm 1.25" long eye relief
by Takahashi
Star Diagonals (1)
1.25" Prism diagonal
by Takahashi
Photographic Accessories
Camera Adapters (3)
35mm wide mount coupling for FS-78, FS-60C, and Sky 90 II
by Takahashi
Eyepiece Projection adapter, needs T-ring
by Takahashi
Camera angle adjuster FS-78/60C/60E/Sky 90
by Takahashi
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Takahashi FS-60C system chart 25 KB
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Takahashi - FS-60C 2.4" F/5.9 fluorite doublet apo

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Takahashi - FS-60C 2.4" F/5.9 fluorite doublet apo
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Our Product #: FS60
Manufacturer Product #: TFK6004
Price: $860.00  FREE ground shipping - Click for more info
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This compact Takahashi fluorite apochromatic refractor makes an ideal eclipse scope and a super travel and backyard scope for spur-of-the-moment observing . . .

. . . our 38th year