Explore Scientific 127mm f/7.5 Classic White FCD100 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 #: ES127FCD
Explore Scientific Product #: FCD100-127075-01
Recommended Accessories

Product Description

This 5" Explore Scientific ES127 Classic White FCD100 apochromatic refractor has:
127mm f/7.5 fully multicoated triplet optics using a Hoya FPL53-equivalent FCD100 ED element
Dual-speed 2.5" Hexagonal 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
Extended product lifetime warranty

With a 5" (127mm) aperture, this Explore Scientific Classic White ES127 FCD100 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 the premium Hoya FCD100 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 FCD100 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 FCD100 (Dense Fluor Crown) glass, the Hoya equivalent of 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, particularly those with apertures in the ES127 class. Relying on technological innovation, Explore Scientific has successfully launched the mass production of high-performance optical glass at the apex of the FCD family. Combining it with optical glass of high refractive index allows them to achieve unprecedented advanced chromatic aberration correction. Hoya FCD100 is considered the best glass ever produced by Hoya.

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 2.5" Hexagonal 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’ve had this scope since it was introduced by ES. As already mentioned by other reviewers, it has outstanding optics. I did upgrade my focuser to a Feathertouch. The original focuser was extremely difficult to remove. I used two band wrenches to finally remove it. Even then, it was difficult to remove. The original focuser was good but the FT made the scope even better and more precise. (Posted on 8/29/2021)
Review by:
I bought this refractor to replace my AT10RCF when it became too heavy for me to handle safely - bad shoulder And while I miss the AT10, this OTA has won me over. I can now do wider angle narrowband imaging which I should have been doing years ago do to my highly light polluted sky.

I presume ES still has the Feathertouch focuser option and I highly recommend going that route from the get-go. The OEM focuser is "ok", and performs adequately, but it's not a Feathertouch. I don't know about the newer OTAs, but its impossible to remove the stock focuser from mine - must be glued on! Wayne at Starlight says he can remove it but I'm of the "if it ain't broke, don't fix it" mentality, and as I said the focuser performs decently. Other than that, great little refractor at a good price. (Posted on 12/4/2019)
Review by:
This refractor is excellent. I purchase directly from ES, and ES support during the purchase process was super. Razor-sharp stars with no colored fringes. Bang-for buck, it is better than its pricier carbon finder sibling. It is light enough to easily handle, so I couldn't see paying for carbon fiber, as I would have had to purchase the same mount for either.

One small thing that annoyed me is that the scope comes with two adapters for its 2.5" drawtube, but neither is the adapter you need to use with the Bresser/ES 3" 0.7x reducer. I bought this scope for the 2017 total solar eclipse, so I bit the bullet and purchased the 0.7x reducer to get a wider field, but I have subsequently purchase the 1.0x TS-Flat2 2" flattener and a Williams-Optics 0.8x P-Flat6a-III flattener/reducer. Watch out, you will need an adapter at the time of this writing in order to use a WD-Dig2a nose piece from WilliamOptics (or less expensive equivalents from eBay or AliExpress) to use the P-Flat6a-III. RafCamera on eBay made the the adapter for me. WO tells me that they will make that adapter soon. (Posted on 9/9/2019)
Review by:
I had always wanted a good refractor of decent size but always found them out well out of my budget. After reading reviews for this scope I decided to give it a try as this was in my price range. I was not disappointed. The optics are crisp and clear and the color correction excellent. My only criticism is the scope was originally advertised as having a Crawford focuser. Mine does not and I notice that is no longer in the description. (Posted on 8/14/2019)
Review by:
I have taken this refractor to several events and have great views and I have used it for Astrophotography and it is much better than my Schmidt Cassegrain scope (Posted on 8/1/2019)
Review by:
This is by far the best triplet refractor you can buy for around $2K. As other say, views of the Moon, Jupiter, and Saturn are simply stunning. Initially, I had to send mine to ES as the focuser was completely messed up, but they paid to have it shipped and I had it back properly repaired within two weeks. I've always had great support from the staff at ES and can't recommend their products enough. (Posted on 7/29/2019)
Review by:
I did some visual and some astrophotography with this scope in the summer with a friend of mine that had one. OMG the views of Jupiter were so clear and razor sharp. Moon was stunning to say the least. There's a clarity with a good refractor that cant be touched by a cassegrain or reflector. I used to be a big cassegrain guy but have since moved to refractors. The shots taken with this scope of the moon and Jupiter were amazing. I have wanted one of these ever since that night. you wont be disappointed with this scope for Visual or AP, trust me.... (Posted on 10/30/2018)
Review by:
Purchased the 127mm Triplet ED to replace my 8” Meade LX90. Much sharper visually and great for Astrophography. I would highly recommend this scope (Posted on 10/6/2018)
Review by:
I recently ventured into the world of Refractors with this Explore Scientific 127mm. The ES 127 mm is now my "go to" scope for 95% of all my astrophotography. The optics are simply outstanding compared to my 12" SCT. Its a pleasure to use, tremendous clarity, less futzing around focusing. I use mine with a CGX mount and would highly recommend this to anyone who wants to invest in a great telescope that produces razor sharp imagery. (Posted on 10/6/2018)
Review by:
I recently ventured into the world of Refractors with this Explore Scientific 127mm. The ES 127 mm is now my "go to" scope for 95% of all my astrophotography. The optics are simply outstanding compared to my 12" SCT. Its a pleasure to use, tremendous clarity, less futzing around trying to find targets. I use mine with a CGX mount and would highly recommend this to anyone who wants to invest in a great telescope that produces razor sharp imagery. (Posted on 10/6/2018)
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Supplied Accessories

  • Dual tube rings with Vixen-style dovetail
  • 2.5" dual speed Hexagonal focuser
  • Retractable dew shield
  • Dust covers
  • Finderscope base