ES152CF 152mm f/8 ED triplet refractor, with carbon fiber body

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This 6" Explore Scientific ES152CF apochromatic carbon fiber refractor has:

• 152mm (6") fully multicoated f/8 apochromatic triplet optics using a Hoya FPL51-equivalent ED element
• lightweight low thermal expansion carbon-fiber body
• dual-speed 3” Feather Touch rack-and-pinion focuser with 2" accessory holder
• 2” dielectric star diagonal with 2” and 1.25” brass compression ring eyepiece holders
• 8 x 50mm right-angle illuminated erect-image/right-reading polar finderscope
• dual split mounting rings with handle and Losmandy-style "D-plate" dovetail
• heavy-duty travel case
• extended lifetime warranty

The 6" (152mm) aperture Explore Scientific ES152CF uses a premium Hoya ED glass element and state-of-the-art optical multicoatings in its apochromatic air-spaced ED triplet optics. The result is visual and photographic images that are essentially free of the annoying halo of unfocused violet light (chromatic aberration) that mars the view of bright stars and solar system objects in lesser scopes, despite the scope’s large aperture, and even at very high magnifications.

The 152mm Explore Scientific triplet optics are even more appealing when you consider that this Explore Scientific apo is loaded with features other manufacturers charge extra for (or don’t even have available) – such as a 3" Feather Touch focuser, an illuminated 8 x 50mm right-angle finderscope with erect right-reading images, a 2" dielectric star diagonal with 1.25" and 2" compression ring accessory holders, and a carrying case.

The body and dew shield of the 152mm Explore Scientific are made of high strength, low weight, low thermal expansion carbon fiber. This keeps the scope sharply focused as the ambient temperature changes during critical long-exposure CCD imaging.

The Explore Scientific ES152CF is a natural on an equatorial mount as the heart of your observing system. In addition to it's superb visual images, it’s an excellent astrograph for both serious wide field deep space imaging and crisp solar system imaging.

Features of this Telescope . . .

  • ED triplet refractor optics: 152mm (6") aperture, 1216mm focal length, f/8 focal ratio three-lens air-spaced optical system. The optics use a center lens element of Hoya FCD1 (Dense Fluor Crown) glass, the Hoya equivalent of FPL-51 ED (Extra-low Dispersion) glass. This ED element produces superior sharpness and color correction by essentially eliminating chromatic aberration, the “false" color fringing seen around bright objects when light rays pass through standard crown-and-flint doublet objectives, particularly those with apertures in the 152mm class. The result is to reduce spurious color halos and fringing to vanishingly low levels for both imaging and visual use.
  • Fully multicoated optics: The triplet objective lens of the ES152CF has EMD™ (Enhanced Multilayer Deposition) antireflection multicoatings on all air-to-glass surfaces for high light transmission, minimal light scatter, and excellent contrast.
  • Internal light baffles: Contrast-enhancing internal light baffles and a specially darkened tube interior provide dark sky backgrounds and high terrestrial contrast.
  • Collimatable optics: One of the bonuses of owning a refractor is that, compared to standard reflector telescopes, they almost never require realigning of the optics (collimation). However, any air-spaced refractor telescope may require optical recentering if the lens elements are knocked out of alignment by a heavy blow during shipping or use. Removing the dew shield will give you access to the lens centering screws in the sides of the lens cell, which you can then adjust yourself by referring to the supplied instructions. You can also send your scope to Explore Scientific’s Service Center for precision alignment. A standard service charge applies for factory realignment.
  • Carbon fiber body: The body and dew shield of the 152mm Explore Scientific are made of woven carbon fiber fabric, encapsulated in epoxy. Carbon fiber, the same material used to fabricate much of the fuselage and wings of the new Boeing 787 Dreamliner passenger jet, has a high strength-to-weight ratio to keep the scope almost 20% lighter than comparable aperture aluminum-body scopes. In addition, it has low thermal expansion characteristics when subjected to temperature variations. This helps to keep the instrument sharply focused as the ambient temperature changes, which is particularly important during critical long-exposure CCD imaging.
  • Dew shield: The supplied removable carbon fiber dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves the contrast, similar to the effect of the lens shade on a camera lens, when there is excessive ambient light at night, such as a neighbor’s backyard security light. A slip-on metal dust cap for the dew shield is standard.
  • Dual speed 3" Feather Touch rack-and-pinion focuser: Optics as good as the ES152CF deserve a premium heavy-duty focuser . . . and the ES152CF has a decidedly premium focuser. It's the made-in-the-USA no-backlash rack-and-pinion Feather Touch 3" focuser from Starlight Instruments. This precision piece of engineering has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with a 10:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during high magnification visual observing and critical DSLR or CCD imaging. The large focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather.

    The focuser can be rotated 360° for the best photographic composition without affecting the focus, which is locked in place with a large brass knob on the top of the focuser. Three large brass knobs lock the focuser at any desired rotational orientation. The focuser drawtube has a scale marked on both sides in centimeters and 1mm increments. This lets you note individual focuser positions for easy return to the correct focus when switching between visual use and photography. A knob underneath the focuser lets you adjust the tension on the built-in drawtube brake to accommodate varying eyepiece/photo accessory loads.

  • 2" dielectric star diagonal and compression ring eyepiece holders: The supplied standard equipment 2" mirror star diagonal of the ES152CF slips into the 3" focuser drawtube’s 2" eyepiece/accessory holder. The 2" diagonal has 99% reflectivity dielectric mirror coatings for high light transmission. The star diagonal uses a non-marring soft brass compression ring to hold 2" eyepieces in place. The compression ring won’t scratch the barrel of your 2" eyepieces as an ordinary thumbscrew can. A supplied 1.25" accessory adapter slips into the 2" diagonal to let you use 1.25" eyepieces in the 2" diagonal. The 1.25" accessory adapter can also be inserted into the 2" accessory holder on the focuser drawtube to let you use a 1.25" image erecting diagonal, or 1.25" photographic accessories. Like the 2" eyepiece holder on the diagonal, the 1.25" adapter also uses a non-marring soft brass compression ring to hold 1.25" star diagonals and accessories in place.
  • Finderscope: The Explore Scientific ES152CF comes with a right angle 8 x 50mm right-anglepolar alignment finderscope with a wide 6° field of view. It is mounted in a quick-release bracket using dual-ring six-point collimation. The finder is fully-multicoated to insure maximum brightness and contrast. A precision-polished roof prism in the finder produces images that are right-side-up and left-to-right correct. In other words, the sky is not upside-down and backwards as it is in most straight-through finders. You can independently focus both the finderscope objective to make the stars pinpoint sharp and sharply focus the reticle in the finder’s illuminated reticle eyepiece. 
  • Mounting rings and dovetail: The ES152CF has dual split mounting rings mounted on a Losmandy-style "D-plate" dovetail that fits the Losmandy-style dovetail slot on the head of many of the most popular heavy duty German equatorial mounts. Such mounts include the Celestron CGEM DX and CGE Pro, the iOptron iEQ45, the Losmandy G11 and HGM Titan, and the Software Bisque Paramount MX go-to equatorial mounts, among others. A spacer/stabilizing bar on the top of the rings provides a carrying handle that makes it easy to transport the optical tube and install it on your equatorial mount.
  • Extended lifetime warranty: This individually serial numbered Explore Scientific telescope is backed by a limited one year warranty, which will be extended to an Explore Scientific transferable lifetime limited warranty when its warranty card is registered with Explore Scientific within 60 days of purchase. Full details on this unique transferable lifetime warranty.
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.
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).

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.

0.76 arc seconds
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.
35 lbs
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
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:
Binary and Star Cluster Observation:
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:
1 year, extendable to lifetime
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ES152CF 152mm f/8 ED triplet refractor, with carbon fiber body

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ES152CF 152mm f/8 ED triplet refractor, with carbon fiber body
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Our Product #: ES152CF
Manufacturer Product #: TED15208-CF
Price: $6,699.99  FREE ground shipping - Click for more info
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MSRP: $14889.99

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This big and optically excellent 152mm (6”) Explore Scientific air-spaced ED triplet apochromatic refractor has a carbon fiber body and 3" Feather Touch focuser and is superb for critical long-exposure DSLR and CCD imaging.

. . . our 34th year