Explore Scientific AR127 5" f/6.5 achromatic doublet refractor


Availability: Out of stock

This 5" Explore Scientific achromatic refractor optical tube is a big performer, both inside the solar system and out in the realm of the nebulas and galaxies, at a not so very big price.
Our Product #: ES127D
Explore Scientific Product #: DAR127065-01

Product Description

From June 9th through June 30th 2019 you will receive a free Explore Scientific 70 Degree 25mm Eyepiece with purchase of this telescope.
This 5" Explore Scientific ES127D achromatic doublet refractor has:
Big 5" aperture fully multicoated achromatic doublet refractor optics
Collimatable objective lens cell for fine-tuning the images
Big 8 x 50mm finderscope
2" dielectric star diagonal with 1.25" eyepiece adapter
Tube rings with carry handle and Vixen-style dovetail plate
Extended lifetime transferrable warranty

This highly portable 5" Explore Scientific ES127D achromatic doublet refractor optical tube (only 35" long, with a weight of 15 pounds) is an exceptional value. It has a 127mm (5") diameter multicoated doublet objective lens (825mm focal length f/6.5). Its diffraction limited optics are sharp and well suited to serious deep space observing of binary stars, star clusters, and the brighter nebulas and galaxies, in addition to excellent high contrast planetary and lunar images. The objective lens cell is fully collimatable, so you can optimize your image quality.

The 5" Explore Scientific ES127D is a great grab-and-go scope for quick looks at the sky when mounted on a suitable altazimuth mount. It's good enough optically to be the heart of a reasonably-priced serious observing system when mounted on one of the many equatorial mounts and go-to altazimuth mounts from Celestron, iOptron, and others.

Some chromatic aberration is visible on stars and objects of 2nd or 3rd magnitude and brighter, as you would expect in an achromatic refractor with such a fast focal ratio. However, the spurious color is well controlled and not unreasonable, thanks to careful optical design, and has little effect on deep space observing. Most observers feel the relatively limited amount of chromatic aberration visible is a small price to pay for the scope's many other virtues of portability, sharpness, contrast, and optical clarity.

Features of This Optical Tube . . .

Achromatic refractor optics: 5" (127mm) aperture, 825mm focal length, f/6.5 air-spaced crown and flint glass doublet lens. Tube diameter is 5.13" (130.4mm) and the tube length with dew shield installed is 34" (864mm). Scope weight is 15 pounds (6.82 kg).

Collimatable lens cell: The 5" Explore Scientific lens is precision collimated at the factory to give optimum performance. Although you may never need to adjust optical alignment, the ES127D allows for collimating the lens set should the telescope ever require it due to a fall or very rough handling.

Multicoated optics: Fully coated on all surfaces with multiple layers of antireflection materials for high light transmission and good contrast.

Internal light baffles: Multiple internal knife-edge baffles in the optical tube mask and deflect unwanted stray light for improved contrast.

Dew shield: The removable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves visual and photographic contrast by shielding the lens from off-axis ambient light (the neighbor's yard light, moonlight, etc.)

Dust covers: Front and rear dust covers are provided.

Dual-speed Crayford-style focuser: 2" focuser, with adjustable tension and lock knobs. The 2" eyepiece holder uses a non-marring brass compression ring to hold the supplied 2" star diagonal in place without scratching the diagonal barrel. The precision-made 2" focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 10:1 ratio reduction gear microfine focusing. This provides exceptionally precise image control during high power visual observing or critical DSLR or CCD imaging. The focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather.

Dielectric star diagonal: 90° viewing angle first surface mirror 2" star diagonal with 1.25" eyepiece adapter. The diagonal uses durable 99% reflectivity for maximum light transmission and long life.

Finderscope: 8 x 50mm straight-through achromatic design, in a dual-ring six-point adjustment bracket with a quick release mounting shoe. Focuses by loosening the trim ring behind the objective lens cell, screwing the lens cell in or out to focus, and tightening the trim ring to lock in the correct focus.

Rings and dovetail tube mount: The optical tube comes with two split and hinged tube rings for installing the optical tube on your mount. The rings are connected to a dovetail mounting plate that slips into the standard dovetail groove on Astro-Tech Voyager, Explore Scientific, Celestron, and iOptron mounts, among others. A carrying handle is conveniently fitted to the top of the tube rings

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.

Tech Details

Aperture 5"
Binary and Star Cluster Observation Very Good
Focal Length 825mm
Focal Ratio f/6.5
Galaxy and Nebula Observation Good
Highest Useful Magnification 236x
Lunar Observation Great
Weight 15 lbs
Planetary Observation Very Good
Resolution 0.91 arc seconds
Telescope Type Refractor
Visual Limiting Magnitude 13
Warranty Limited Lifetime


Review by:
Great scope for the price. I owned one previously but sold it to fund the purchase of a triplet APO. However, I bought another during the ES sale. It is a fast achro., so CA is visible. I keep a Baader Semi-Apo filter in the diagonal which cuts most of the violet fringe. Compared to the APO, low and medium power viewing shows no difference. At higher power on a bright object, the CA is slightly visible with some contrast loss compared to the APO. Considering a 5" APO will cost at least 4-5 times more, the AR-127 is fine for visual use. ES also includes the top handle and diagonal when most other manufacturers do not. Astronomics still had it for the sale price when the other retailers did not, so Kudos to Mike. (Posted on 3/15/2023)
Review by:
I bought this AR127 refractor used from EBay seller in Germany more than a year ago. It is a robust and reliable scope, which will never let you down. The contrast and sharpness is stunning. You can easily cope with the slight CA when observing the brightest Stars. Highly recommended for the easy visual observation by using alt-atz mount !
(Posted on 10/27/2022)
Review by:
I purchased this telescope a couple years ago and after 2 years of use, I can say that this is a lot of scope for a little money. Images are sharp, focuser is top notch and optics are outstanding. I highly recommend this scope for anyone looking for a portable, high quality refractor. Great all around scope. (Posted on 10/31/2019)
Review by:
This is one of the best telescopes on the market for this low price. There are chromatic limitations to the doublet, but the price difference to correct that would be at minimum $1500. Compared to the best 6" commercial scopes on the market, it takes the lead by miles (or kilometers if you prefer). (Posted on 10/17/2019)
Review by:
This is a telescope that I used to use for a little while before selling it to get a newer one that performs better. Besides that this telescope is good for imaging both the solar system and deep sky objects. When I used to use this telescope I paired it with my Celestron AVX because it’s somewhat light weight at least when comparing to other telescopes. I would recommend this to anyone wanting to get a 5” telescope used for astrophotography. (Posted on 1/2/2019)
Review by:
If just starting out, Explore Scientic is a great scope to go with for the price. It has good optics and other great features the expensive scopes have. You can’t go wrong. (Posted on 11/21/2018)
Review by:
I purchased the AR127 over the AR152 because of portability. I wanted a telescope that is manageable to move, and this was it. So glad I did not get the AR152 as the AR127 is just the perfect size for me (I'm 5'9" and 170lbs). It fits very well on the EXOS2-GT mount and the Vixen Porta II, and is a very high-quality scope. The build and accessories are excellent. As for the views, they are excellent, too. I wanted at least 5 inches of aperture as an upgrade from the ST80 I was using, and this scope delivered. There is some CA on very bright objects (the moon, Venus, Mars, Jupiter, and bright stars), but for galaxies (Andromeda) and open (Pleiades) and globular clusters, the AR127 is great. Compared to my more recently purchased 180mm mak-cass, I can still use the AR127 as a grab-n-go scope on the Porta II alt-az mount. Very happy with this Explore Scientific 127mm achromat doublet. (Posted on 11/15/2018)
Review by:
For my needs. mostly just observing, scope and price is right on. Lucked up and got mine on sale. I'm sure the higher priced triplets are better in some ways but not sure its worth all that much more money especially for basic observing. Field of view is very adequate for general viewing, as it is when looking at brighter DSOs. Contrast is great. Wish it was a little lighter in weight but there again its not near as expensive as the carbon fiber ones. All around very pleased. (Posted on 10/10/2018)
Review by:
I teach high school astronomy and this is my students favorite scope at our school star parties. It’s durable, it’s a great size (students think it’s a big scope), it’s has good contrast (I use a Baader semi apo filter in it). The knobs are a good size and I use it on Bressler EQ (with duo motor set up - not the go- to version) . The finder scope is easy to use. All around ideal scope for educational purposes! (Posted on 10/7/2018)
Review by:
I'm quite surprised this telescope hasn't been reviewed and rated here at Astronomics. This refractor is a gem in the rough.. rough market of telescopes, esp. achromatic refractors. Lot's of amateurs browsing for an achromat may automatically think of this F-6.5 telescope as a 'fast focal length' and so likely to have problems with chromatic abberation, aka: CA. NOT SO!! A 'fast' FL telescope is focal ratio 3,4, and 5. Middle focal ratio scopes are focal ratio 6-9. And long focal ratio scopes are about F-10 and up. This wonderful telescope if an F-6.5, so it is very good at both deep space objects as well as solar system viewing. This large refractor is manageable thanks to it's intermediate focal ratio, and the views are bright, crisp and very sharply defined - color is very well controlled. I have a 'semi-apo' filter that I was sure I'd need. NOPE! I haven't bothered with it. The views are so good - just as are. The Moon is breathtaking. So crisply presented.. looking down in the diagonal is like you were looking out of the Apollo CM as it approached the surface. I use a TeleVue 2.5x Powermate w/ Meade 82° field 14mm Ultra Wide ep. So fine!

Saturn is excellent. Textbook! I often use this refractor on the Twilight II mount, along with my C9.25" SCT or C102gt refractor. (Posted on 8/4/2017)
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Supplied Accessories

  • Dual tube rings with Vixen-style dovetail and carry handle
  • 8 x 50mm straight-through finderscope
  • 2" dual speed Crayford focuser
  • 2" dielectric star diagonal with 2" and 1.25" brass compression ring eyepiece holders
  • Removable dew shield
  • Dust covers