Explore Scientific ES127 127mm f/7.5 "Essential Series" FCD-1 ED Triplet Refractor


Availability: In stock

This big 127mm (5") Explore Scientific Essential Series air-spaced ED triplet apochromatic refractor is loaded with quality optical performance at a surprisingly reasonable price for a scope of its size and optical quality . . .
Our Product #: ES127B
Explore Scientific Product #: ES-ED127075-03
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Product Description

This 5" Explore Scientific ES127 "Essential Series" apochromatic refractor has:
127mm f/7.5 fully multicoated triplet optics using a Hoya FPL51-equivalent ED element
Dual-speed 2" rack and pinion focuser with 10:1 ratio fine focusing
Mounting rings with dovetail for use on a Vixen-style altazimuth or German equatorial mount
Finderscope base installed on OTA
2" 99% reflective dielectric star diagonal
Extended product lifetime warranty

With a 5" (127mm) aperture, this Explore Scientific "Essentials Series" ES127 ED triplet refractor gathers 55% more light (with nearly 25% higher resolution) than the more common size 102mm (4") doublet and triplet refractors that often cost nearly as much as the ES127.

The Explore Scientific ES127 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 scope's relatively large aperture, and even at very high magnifications.

The Explore Scientific ES127 is a natural on an equatorial mount as the heart of your primary observing system. In addition, it's an excellent astrograph for serious wide field imaging, as well as crisp solar system imaging. Considering its surprisingly reasonable price for a 5" apochromatic triplet and in view of the great optical performance that comes as standard equipment, the 5" Explore Scientific ES127 is a terrific buy!

Features of this Telescope . . .

ED triplet refractor optics: 127mm (5") aperture, 952mm focal length, f/7.5 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, particularly those with apertures in the ES127 class. The result is to reduce spurious color halos and fringing to vanishingly low levels.

Fully multicoated optics: The ES127 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 body has contrast-enhancing internal light baffles and a specially darkened tube interior to provide dark sky backgrounds and high 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 retractable 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 slip-on metal dust cap is standard.

Dual speed 2" rack and pinion focuser: The rotating 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 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 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. Lock knobs let 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 terminates in a non-marring 2" compression ring accessory holder. Two 2" draw tube extensions are included to let adjust the back focus when using a diagonal and eyepieces versus a camera.

Mounting rings and dovetail: The ES127 has dual split mounting rings with a dovetail plate that fits the Vixen-style dovetail slot on the head of many of the most popular medium capacity German equatorial mounts. Such mounts include Celestron and iOptron go-to 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. There is a mounting shoe for an optional finderscope installed on the body of the scope.

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 Life of The Product limited warranty when its warranty card is registered with Explore Scientific within 60 days of purchase. Full details on this unique transferable lifetime warranty.

Tech Details

Aperture 5"
Binary and Star Cluster Observation Very Good
Focal Length 952mm
Focal Ratio f/7.5
Galaxy and Nebula Observation Good
Highest Useful Magnification 271x
Lunar Observation Great
Weight 22 lbs.
Planetary Observation Very Good
Resolution 0.91 arc seconds
Telescope Type Refractor
Visual Limiting Magnitude 13
Warranty 1 year, extendable to lifetime


Review by:
I bought this OTA a couple of years ago at a much higher price to replace an AT10RCF which was just too heavy for me to handle any longer. Of course, long focal length imaging is no longer possible but light pollution has forced me into narrowband imaging anyway - and this scope is perfect for it.
One thing I would definitely recommend is purchasing the upgraded focuser. I was planning on replacing the OEM focuser with a Feathertouch but the stock focuser is practically welded on - or extremely strong loctite was used anyway - no way that thing is coming off - although Wayne at Starlight Instruments says they can do it. But I have added a Rigel motordrive to the focuser and the assembly works reasonable well. (Posted on 10/26/2019)
Review by:
The optics is very good for the price of the scope. I just wish it had a better focuser. (Posted on 10/24/2019)
Review by:
I bought this scope a few weeks ago. I bought it for the focal length and the triplet ED objective. The OTA seems we’ll constructed and it looks like a bazooka compared to my smaller scopes. I don’t do visual so I can’t comment on the diagnonal. The focuser seems kind of cheap but I planned on replacing it with a Moonlite. So far I’m happy with the images I’m pulling down. (Posted on 8/1/2019)
Review by:
After lugging around a 12" dob and an 8" Newtonian, I wanted something a little more portable. After much research I sprang for the ES 127mm. Despite reading all the reviews and watching videos I was a bit surprised just how big the scope is! Ha. Silly me. It didn't take long for me to fall in love with it. The optics are so sharp and the colors are spot on. It is quickly becoming my favorite scope. It works wonders with imaging and after a year I can say this scope will be in my tool box for a long time. The focuser works well, but it is a touch weak with heavy cameras. I thought this scope would do a wider field than my 8" Newt, but I was wrong. Now I need something wider...good for astronomics, bad for my pocketbook :) Buy this scope, you won't be disappointed!
(Posted on 1/14/2019)
Review by:
Originally I purchased an Explore Scientific 102mm triplet refractor. An excellent scope and perfect for my light capacity equatorial mount but I wanted the bigger one. I traded it up for this 127mm monster. It’s also a great scope and I used it with the same light weight capacity mount. At just under 18 pounds without the finder scope it was portable and so far it’s done it’s best work on the moon and planets. I also used it for the August 2016 eclipse. I highly recommend the scope and defy anyone to find a triplet refractor at this price point. 5 ⭐️ all the way! (Posted on 12/31/2018)
Review by:
I have looked thru a number of ES scopes both carbon fiber and Aluminum. The views thru the FCD1 127mm were stunning!! I was really floored at the clarity these copes provide for visual. I almost bought the carbon fiber version for AP, but wanted a faster focal ratio. I have a friend that images with both the aluminum 127mm essential series and an aluminum 80mm FCD100. I have been impressed with all the ES scopes, although I cant vouch for the Achromatic scopes as I haven't had access to one. If you're doing Astrophotography, at 19lbs, the aluminum OTA is light enough to perform well with most mounts. Consider the Carbon Series if you want less weight. They are also less susceptible to temperature changes. I own an ES 115mm f5.5 FPL-53 scope and couldn't be happier with it. I only got the 115mm because I wanted the fast f5.5 focal ratio). Fine optics, Light weight, Great price. You wont be disappointed!! (Posted on 11/29/2018)
Review by:
Well, besides looking like a futuristic weapon mounted on a tripod... This thing is AWESOME. My neighbor came outside and asked what I was shooting at...

The views are astonishing. I have this and a 11" sct. I use this most of the time for planetary and some deep space. Crystal clear straight from Astronomics, I truly was not expecting to have the "wow" moment at first light. (Posted on 10/8/2018)
Review by:
This was my first refractor, and I love it. The quality feel of an ES OTA is very reassuring, and the optics do not disappoint. I also purchased the ES field flattener, and stars are round all the way to the edges. It's an absolute pleasure to use, and I know I will enjoy it for a long time to come. (Posted on 10/6/2018)
Review by:
This was my first refractor in decades. I had been using an AT10RCF and while it was also very good, it was getting too heavy for me to handle. The ES127 has turned out to be perfect for me both in weight and imaging capability.
The stock focuser is adequate to handle my QSI683wsg8 camera but in hindsight, paying more for the FeatherTouch option would have been a good move since the stock focuser appears to be glued in. But it's smooth and reasonably repeatable.
And for the record, I paid more last year than the current price here at Astronomics - this is a great buy! (Posted on 10/6/2018)
Review by:
I've had this scope for about a year now and it's absolutely awesome. Great wide field views with nebula, galaxies, and stars resolved perfectly. (Posted on 10/6/2018)
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Supplied Accessories

  • Dual tube rings with Vixen-style dovetail
  • 2" dual speed rack and pinion focuser
  • Retractable dew shield
  • Dust covers
  • Finderscope base
  • 2" 99% reflective dielectric star diagonal