Pro 100ED 100mm f/9 ED doublet apochromatic refractor

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This Sky-Watcher PRO 100ED apochromatic refractor has:

• 100mm f/9 apochromatic doublet optics using Schott glass and an FPL53- ED element
• dual-speed 2” Crayford focuser with 10:1 ratio fine focusing
• 2” dielectric star diagonal with 2” and 1.25” eyepiece holders
• two 1.25” Long Eye Relief eyepieces (20mm and 5mm)
• 8 x 50mm right-angle finderscope
• dovetail shoe for installing on a Celestron CG-5 mount or any Vixen-style altazimuth or German equatorial mount
• two-year warranty

    The Sky-Watcher PRO 100ED from Celestron uses a crown glass element of premium Schott Glass, an FPL-53 ED glass element, and state-of-the-art optical multicoatings in its apochromatic ED doublet optics. Combined with the moderate focal ratio, this results in images with visibly less chromatic aberration than you find in refractors with a similar aperture but faster focal ratio. In addition to the lack of chromatic aberration’s annoying halo of unfocused violet light around bright stars and solar system objects, there is no loss in contrast such as you will find in reflector and catadioptric scopes that have a secondary or diagonal mirror hanging in the light path to scatter light..

    The 100mm Sky-Watcher doublet optics are even more appealing when you consider that this Sky-Watcher apo is loaded with features other manufacturers charge extra for (or don’t even have available) – such as an 8 x 50mm right-angle finderscope, a 2” dielectric star diagonal with 1.25” and 2” compression ring accessory holders, two 1.25" LE (Long Eye Relief) eyepieces (LE20mm and LE5mm); and a foam-lined aluminum-clad carrying case.

    The Sky-Watcher PRO 100ED has enough premium high contrast/high resolution optical performance to let you use it on an altazimuth or equatorial mount as the heart of your observing system. Its light weight (only 6.6 pounds) doesn’t require a big and expensive mount, so it’s easy to afford and easy to take out and set up for observing on a moment’s notice. Considering its surprisingly low price for an apochromatic doublet, adding in the extra features you get at no extra cost, and in view of the great optical performance that comes as standard equipment, the 100mm Sky-Watcher PRO 100ED is a terrific buy!

Features of this telescope . . .

  • Apochromatic ED doublet refractor optics: 100mm (3.94”) aperture, 900mm focal length, f/9 focal ratio. The optics use a crown glass front element of premium Schott Glass, from one of the world’s most-respected glass manufacturers. The ED element is precision-polished from high grade FPL-53 ED (Extra-low Dispersion) glass. This ED element produces superior sharpness and color correction by minimizing the chromatic aberration, the “false” color fringing seen around bright objects when light rays pass through standard crown-and-flint doublet objectives. The result is to reduce spurious color halos and fringing to vanishingly low levels.

  • Fully multicoated optics: Each air-to-glass surface in the Sky-Watcher PRO 100ED doublet objective lens has MHC (Metallic High-Transmission Coating) 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 in the tube and focuser drawtube and a specially darkened tube interior provide dark sky backgrounds and high terrestrial contrast.

  • Dew shield: The supplied 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 observing during the day or when there is excessive ambient light at night, such as a neighbor’s backyard security light. The 6.6 pound optical tube measures 36.22” long, including the dew shield. A slip-on metal dust cap is standard.

  • Dual speed 2” Crayford focuser: The precision-made no-backlash focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 10:1 reduction gear microfine focusing. 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. Lock knobs lets you adjust the tension on the drawtube to accommodate varying eyepiece/photo accessory loads, as well as firmly lock in a photographic focus.

  • 2” dielectric star diagonal: The supplied standard equipment 2” mirror star diagonal of the PRO 100ED slips into the focuser drawtube’s 2” eyepiece/accessory holder. The 2” diagonal has 99% reflectivity dielectric mirror coatings for high light transmission. A supplied 1.25” accessory adapter slips into the 2” diagonal to let you also use 1.25” eyepieces. The 1.25” accessory adapter can also be inserted directly into the 2” accessory holder on the focuser drawtube to let you use a 1.25” image erecting diagonal, or 1.25” photographic accessories.

  • Supplied eyepieces: Two 1.25” long eye relief eyepieces are supplied as standard equipment – a 20mm (45x) and a 5mm (180x).

  • Finderscope: The Sky-Watcher PRO 100ED comes with an 8 x 50mm right-angle finderscope that is fully-multicoated to insure maximum brightness and contrast.

  • Mounting dovetail: The Sky-Watcher PRO 100ED apo from Celestron has dual hinged split-ring tube rings and a dovetail mounting bar that fits directly into the Vixen-style dovetail slot on the head of many of the most popular medium capacity altazimuth and German equatorial mounts. Such mounts include the Astro-Tech Voyager altazimuth, the Celestron CG-5 Advanced Series go-to equatorial, the Meade LXD-75 go-to equatorial, and the Vixen Sphinx and Great Polaris Deluxe equatorial mounts and Porta altazimuth mount, among others.

  • Shipping/storage case: The scope comes in foam-fitted aluminum-clad shipping/storage case.

  • Two-year warranty: The Sky-Watcher PRO 100ED doublet apo from Celestron is protected by a two-year limited warranty against flaws in materials and workmanship.
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.
225x
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).

12.5
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.

900mm
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.

f/9
Resolution:
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.

1.16 arc seconds
Aperture:
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.
3.94"
Weight:
The weight of this product.
6.6 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.
Refractor
 
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. 
Yes
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.  
Great
Planetary Observation:
Very Good
Binary and Star Cluster Observation:
Very Good
Galaxy and Nebula Observation:
Good
Photography:
Yes
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.
Yes
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. 
Yes
Planetary Photography:
Yes
Star Cluster / Nebula / Galaxy Photography:
Yes
Warranty:
2 years
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  • 100mm f/9 ED doublet apochromatic optics
  • Split hinged tube rings with a Vixen-style dovetail
  • 8 x 50mm right-angle finderscope
  • 2" dual speed Crayford focuser
  • 2” dielectric star diagonal with 2” and 1.25” eyepiece holders
  • 20mm (45x) and a 5mm (180x) long eye relief 1.25” eyepieces
  • Dew shield
  • Dust covers
  • Foam-fitted carrying case.
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Sky-Watcher - Pro 100ED 100mm f/9 ED doublet apchromatic refractor

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Sky-Watcher - Pro 100ED 100mm f/9 ED doublet apchromatic refractorAnother view of the Sky-Watcher 100mm Pro doublet apo refractor.The hard case for the Sky-Watcher 100mm doublet apo refractor.
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Our Product #: SWP100
Manufacturer Product #: S11120
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This 100mm Sky-Watcher Pro 100ED doublet apochromatic refractor from Celestron is a premium scope with high contrast/high resolution performance and premium accessories at a very attractive price . . .





. . . our 34th year