The 102mm (4-inch) refractor telescope is a go-to not only for beginners looking to jump into the awe-inspiring world of astronomical observations, but also for experienced observers seeking a long-term optic. If you're looking for high quality views of the Moon, planets and brighter deep space objects, the 102mm refractor is an ideal compromise between portability and aperture.
This aperture size is great for observing open star clusters. However, for globular clusters, you may want to explore a refractor with an aperture of at least 120mm. Keep in mind that in many cases, a good quality 4-inch refractor can outperform an average quality 8-inch reflector or catadioptric.
In general, refractor telescopes are one of the most commonly purchased telescopes on the market. First developed in 1609 by Galileo, refractors use a glass lens to form an image. They refract, or bend, parallel light rays to converge at a focal point.
A few refractor benefits are ease of use, high portability, low maintenance, and high image contrast.
Now that we have the basics out of the way, let's dive right into the comparison.
In this article we will cover:
- Explore Scientific's AR102 Review
- Explore Scientific's ED102 Review
- Explore Scientific's ED102-FCD100 Review
Who is Explore Scientific?
Explore Scientific has been a premium manufacturer of astronomy products for over 15 years, having been established July 2008. The company designs and builds telescopes and binoculars that are high quality, durable and affordable. The company is located here in the United States, and has its headquarters in Northwest Arkansas. Explore Scientific has been on a mission to make astronomy more easily accessible and provides a truly transformative experience by giving enthusiasts of all skill levels the tools and guidance they need to explore the skies.
AstroTelescopium reached a distribution agreement with Explore Scientific in order to provide their high quality telescopes, binoculars and telescope accessories to those looking to explore the world above.
The Explore Scientific AR102
If you're looking for a compact, high-quality built refractor that provides nice wide-field deep sky, lunar and planetary viewing, Explore Scientific's AR102 is a great beginner scope choice.
The AR102 (SKU DAR102065-02) is designed with an air-spaced achromatic doublet lens system. Air-spaced objectives allow for the reduction of coma in comparison to oil-spaced objectives. However, with its standard crown and flint glass, slight chromatic aberration is unavoidable. This becomes a more relevant consideration if you are doing astrophotography since chromatic aberration is much more noticeable in images than in visual observations. With the use of specialized filters the color distortion is manageable.
The telescope's objective lens is fully multi-coated. It is designed to reduce glare and light loss, resulting in greater image contrast and sharpness. Open star cluster views are stunning, Venus' phases are apparent, and the Moon provides countless details. Nevertheless, it may be difficult to see detailed features on Mars or to resolve globular star clusters.
This model comes with a high-quality 2" dual speed Crayford-style focuser and this facilitates smooth adjustments during observations. Additionally, the AR102's mounting cradle ring assembly is well made with a 45mm wide Vixen-style dovetail plate that enables easy attachment to most modern equatorial and alt-azimuth mounts.
The 2" dielectric-coated 99% reflective 90° diagonal with a 1.25" eyepiece adapter included with the AR102 is a premium accessory and truly delivers. On the other hand, the 8x50 non-illuminated straight-through finder scope is sufficient but you may find that an upgrade to an Explore Scientific 8x50 illuminated right angle polar finder scope may be a worthy investment.
Additional specifications of the AR102 include:
- 663mm Focal length
- f/6.5 Focal Ratio
- 1.14 arcsec Resolution
- 12.5 Limiting Magnitude
- 25.5" Tube Length w/ Dew Shield Extended
- 11.5 lbs
- Vixen Dovetail
Keeping in mind that the AR102 comes as an optical tube assembly only, a mount will be required unless you already have a sufficient one. If you're looking for a solid manual mount option, the Explore Scientific Twilight I Adjustable Angle Alt-Azimuth Mount is ideal. If you prefer an equatorial mount, however, the Explore Scientific EXOS2-GT Equatorial Mount may be the better choice for you.
The Explore Scientific ED102
The ED102 (SKU ES-ED10207-02) is designed with an air-spaced apochromatic triplet lens system. Similar to the AR102, the air-spaced objective is superior to an oil-based objective in regards to reducing coma.
The triplet lens system allows this scope to produce a flat field of view which is beneficial for astrophotography. Also, this telescope combines genuine HOYA FCD1 ED (extra-low dispersion) glass and proprietary EMD enhanced multi-layer coatings to improve image sharpness, boost contrast and reduce light loss.
If you are delving into deep sky astrophotography, nebulae, galaxies, and star clusters are great targets for this wide-field apochromat. Its versatility stands out, however, as the ED102 is exceptional at producing very detailed lunar and planetary views.
This model includes an adjustable cradle which allows you to securely slide the ED102 up or down to find the perfect balance. There is also a built-in retractable dew shield which protects the objective lens from moisture and miscellaneous stray light. In addition, two extension tubes are included for the 2" rack-and-pinion focuser and that really comes in handy.
Additional specifications of the ED102 include:
- 714mm Focal Length
- f/7 Focal Ratio
- 1.14 arcsec Resolution
- 12.5 Limiting Magnitude
- 30.5" Tube Length w/ Dew Shield Extended
- 12 lbs
- Vixen Dovetail
The Explore Scientific ED102-FCD100
Similar to the ED102, the ED102-FCD100 (SKU FCD100-10207-02) is designed with an air-spaced apochromatic triplet lens system. Building upon the lesser model, the ED102-FCD100 offers greater quality optics with its Hoya FCD100 glass. This specialized glass allows the telescope to attain advanced chromatic aberration correction.
This telescope's objective lens uses proprietary enhanced multi-layer desposition (EMD) coatings on all optical surfaces. These advanced coatings deliver brilliant contrast and improve light transmission for gathering more far red to infrared light which is important during astrophotography use.
The 2.5" hexagonal focuser has a rigid design and can be loaded with up 10 lbs of additional gear. For astrophography purposes, if you're using a large heavy camera, tension can be applied to the focuser with the tension screw underneath in conjunction with the two upper screws locked into place.
This model's dew shield is retractable which shortens the telescope and increases its portability. With reference to portability, the included cradle style tube rings are quite sturdy. There is a carry handle on top which makes set up and carrying of the telescope very easy and stress-free.
Additional specifications of the ED102-FCD100 include:
- 714mm Focal Length
- f/7 Focal Ratio
- 1.14 arcsec Resolution
- 12.5 Limiting Magnitude
- 30.5" Tube Length w/ Dew Shield Extended
- 10.9 lbs
- Vixen Dovetail
There is also a lighter weight upgraded carbon fiber version of this telescope available, SKU FCD100-10207-CF-01, seen below.
So, which one should you choose?
Well, like all choices in life, it really depends.
Of course if cost is a major consideration, you may want to start out with the AR102 ($599.99) rather than the ED102 ($1,199.99) or ED102-FCD100 ($1,999.99).
If you are an experienced astrophotographer, a doublet may not be an option for you, which rules out the AR102. So, your best choice would be one of the triplet options (ED102 or ED102-FCD100).
However, if your intention is to make a long term investment in an optical telescope from which you will be able to get maximum usage, the ED102-FCD100 Carbon Fiber version clearly has the highest quality optics combined with high portability.
Hopefully this article provided additional insight for you. As with all things, take your time, continue to do your research and then decide what is best for you. If you have any additional questions, please don't hesitate to connect with a member of our team.
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