ES80 80mm f/6 ED "Essential Series" triplet apochromatic refractor

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This Explore Scientific ES80 "Essential Series" refractor has:

• 80mm f/6 air-spaced triplet apochromatic optics using a Hoya FPL51-equivalent ED element
• dual-speed 2” rack and pinion focuser with 10:1 ratio fine focusing
• dovetail foot for installing on a Vixen-style altazimuth or German equatorial mount
• dovetail shoe for installing optional finderscope
• extended lifetime warranty

    The Explore Scientific ES80 "Essential Series" refractor 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 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 fast focal ratio of the ES80, and even at very high magnifications.

   The Explore Scientific ES80 is a natural as a lightweight grab-and-go scope for spur-of-the-moment backyard astronomy. It also makes a top-notch travel scope to take across town or around the world. In addition, it’s a nifty fast focal ratio astrograph to piggyback on a larger scope for serious wide field imaging, or you can even use it on a big altazimuth or equatorial mount as the heart of your observing system. Considering its surprisingly low price for an apochromatic triplet, and in view of the great optical performance that comes as standard equipment, the 80mm Explore Scientific ES80 is a terrific buy!

Features of this telescope . . .

  • Air-spaced ED apochromatic triplet refractor optics: 80mm (3.1”) aperture, 480mm focal length, f/6 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 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: The ES80 triplet objective lens 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: The aluminum tube has contrast-enhancing internal light baffles and a specially darkened tube interior to 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.

  • Dew shield: The supplied removable 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. A single thumbscrew holds the dew shield in place, allowing the felt-lined dew shield to be removed from the scope, reversed, slid back onto the optical tube, and stored for transport in only a few seconds. The optical tube measures a compact 18.5” long, including the dew shield. A thread-in metal dust cap for the optical tube is standard.

  • Dual speed 2” rack and pinion 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 a 10:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during high magnification visual observing and critical 35mm 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 drawtube has a scale marked 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. Two knobs underneath the focuser lets you adjust the tension on the drawtube to accommodate varying eyepiece/photo accessory loads, as well as firmly lock in a photographic focus. The focuser has a non-marring 2" brass compression ring equipment holder.
  • Mounting foot: For serious astronomy and astrophotography, the ES80 has an L-shaped dovetail mounting foot that is shaped to fit directly into the Vixen-style dovetail slot on the head of many of the most popular light to medium capacity altazimuth and German VX Series go-to equatorials, the Meade LXD-75 or LX-80 go-to equatorials, and the Vixen Sphinx and Great Polaris Deluxe equatorial mounts and Porta altazimuth mount, among others. In addition, the dovetail has both 1/4"-20 and 3/8” holes that allow you to mount the 7.5 pound scope (including diagonal) directly onto any good photo tripod for casual astronomy or daytime terrestrial observing. A knob on the body of the scope allows you to rotate the tube assemblyand focuser to line up a camera in either a landscape or portrait orientation (or any orientation in between), then temporarily lock the focuser in that position.

  • 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.
160x
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).

12.0
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.

480mm
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/6
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.

1.45 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.
3.1"
Weight:
The weight of this product.
7.5 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:
Fair
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:
Limited Lifetime
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 . . .
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1. James on 4/30/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I absolutely love this scope. I've taken some amazing photo's with it of the night sky. It's focal length is perfect for Orion Nebula and Andromeda Galaxy. The focus knobs are nice and the focus knob lock works great. The only problem I have with it is the illuminated recticle on the spotting scope. I can't seem to get it to glow a bright as I would like. However, that is kind of minor for most people. One of my favorite features is the case. Everything fits perfect and is a very tough case with a cleverly designed latching mechanism.
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We haven't recommended any accessories for this product quite yet... check back soon or call one of our experts (1-405-364-0858).
  • Vixen-style dovetail mount
  • Rotating 2" dual speed rack and pinion focuser
  • Mounting shoe for optional finderscope
  • Dust covers.
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Explore Scientific - 80mm f/6 ED triplet apochromatic refractor

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Explore Scientific - 80mm f/6 ED triplet apochromatic refractorImage showing one of the collimation screws for centering the optics.
 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 4.00 | Users: 1)  Only registered users can submit ratings - Register Here
Our Product #: ES80B
Manufacturer Product #: ES-ED0806-01
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This 80mm Explore Scientific "Essential Series" ED triplet apochromatic refractor is loaded with features and is priced hundreds of dollars less than many competitive 80mm triplet scopes – and even less than many competitive doublets . . .





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