Explore Scientific

BT-120 SF Large Binoculars with 62 Degree LER Eyepieces

Regular price $2,499.99 USD

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BT-120 SF Large Binoculars with 62 Degree LER Eyepieces
$2,499.99 USD
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BT-120 SF Large Binoculars with 62 Degree LER Eyepieces


Description

The Explore Scientific BT-120 SF Giant Binoculars are a premium optical instrument that brings the light-gathering power of a double refractor telescope into a binocular form factor - delivering stunningly bright, detailed views for both astronomy and terrestrial observation. With a massive 120mm objective diameter and 660mm focal length, these binoculars resolve lunar craters, planets, bright deep-sky objects, and distant landscapes with remarkable clarity and contrast. The 45-degree ergonomic viewing angle, soft silicone eyecups, and helical individual focusing system make extended observing sessions genuinely comfortable, whether you're stargazing or scanning a wildlife reserve.

Built to professional standards, the BT-120 SF features a sealed, nitrogen-filled magnesium housing that is fully waterproof and fog-proof, ready for any outdoor conditions. The included 62° 20mm LER eyepieces provide a wide apparent field of view with 15mm of eye relief, and the 1.25" plug-in eyepiece system allows easy swapping for different magnifications. Whether you're an amateur astronomer, a dedicated birder, or a nature enthusiast, the BT-120 SF represents a serious upgrade in immersive, wide-field optical performance.


Key Features

  • 120mm Objective Diameter: Massive light-gathering aperture reveals fine detail on the moon, planets, and deep-sky objects invisible to smaller binoculars.
  • 660mm Focal Length / f/5.5 Focal Ratio: Achromatic refractor Porro optical design delivers bright, high-contrast images across astronomy and terrestrial use.
  • 62° Apparent Field of View: Wide-field 20mm LER eyepieces included, providing immersive views with a 1.8-degree real field of view.
  • 15mm Long Eye Relief (LER): Comfortable viewing for eyeglass wearers and extended sessions, with soft adjustable silicone eyecups.
  • 1.25" Interchangeable Eyepiece System: Plug-in eyepiece compatibility with brass compression ring clamps lets you swap magnifications without tools or alignment headaches.
  • 45-Degree Viewing Angle: Ergonomic angled eyepiece design reduces neck fatigue during long astronomy or birding sessions.
  • Magnesium Housing - Sealed and Nitrogen-Filled: Waterproof (IPX6) and fog-proof in any weather; rugged enough for field and travel use.
  • Extendable Dew Caps: Prevent lens condensation during cold-weather or damp observing conditions.
  • Enhanced Multilayer Deposition (EMD) Coatings: Professional-grade coatings on all optical surfaces maximize light transmission and image brightness.
  • Multiple Tripod Connection Options: Central carrying handle and multiple mount points; compatible with the optional Explore Scientific U-Mount with field tripod for optimal stability.

What's Included

  • BT-120 SF Large Binocular body
  • Two 62° 20mm LER eyepieces (1.25" plug-in)
  • Soft silicone eyecups
  • Extendable dew caps

Why You'll Love It

The Explore Scientific BT-120 SF is the kind of instrument that turns a casual stargazing night into a genuine observing event - trusted by astronomy enthusiasts, nature observers, and serious birders who demand professional-grade optics without compromise. The combination of a 120mm aperture and wide 62° eyepieces creates a deeply immersive experience that smaller binoculars simply cannot replicate. Its all-weather magnesium construction means you can take it to a dark-sky site, a coastal wetland, or a mountain overlook with full confidence in its durability. The ergonomic 45-degree viewing angle and fatigue-free focusing system mean you and your group can spend hours at the eyepiece without discomfort. With the flexibility of interchangeable 1.25" eyepieces and optional nebula and color filters, the BT-120 SF grows with your observing interests and continues to reward you for years to come. For anyone ready to take their visual astronomy or nature observation to the next level, this is the instrument that delivers.


Product Specifications

View Product Specs
Item Number 01-14230
Optical Design Achromatic Refractor Porro
Objective Diameter 120 mm
Focal Length 660 mm
Focal Ratio f/5.5
Apparent Field of View 62 degrees
Real Field of View 1.8 degrees
Coating Type Enhanced Multilayer Deposition (EMD)
Exit Pupil (min) 3.6 mm
Eye Relief 15 mm
Waterproof Yes - IPX6
Housing Material Magnesium (sealed, nitrogen-filled)
Total Length 654 mm
Total Width 290 mm
Total Height 156 mm
Net Weight 8,300 g

FAQ

Do I need a tripod to use the BT-120 SF?

Yes - at 8,300g (over 18 lbs), the BT-120 SF is a giant binocular designed for tripod or mount use, not handheld viewing. Multiple tripod connection points are built into the central carrying handle. For the best experience, the optional Explore Scientific U-Mount with field tripod is highly recommended, as it is specifically designed to support large binoculars like this model and allows smooth, comfortable viewing at the 45-degree eyepiece angle.

Can I use these binoculars with eyeglasses?

Yes. The included 62° 20mm LER eyepieces feature 15mm of long eye relief, which is comfortable for most eyeglass wearers. The soft silicone eyecups are also adjustable, allowing you to fold them down to achieve the correct eye distance whether or not you wear glasses.

Can I change the magnification on the BT-120 SF?

Absolutely. The BT-120 SF uses a 1.25" plug-in eyepiece system, meaning you can swap the included 20mm eyepieces for other compatible 1.25" eyepieces to change magnification. Explore Scientific offers several eyepieces in their 62° waterproof series - including 5.5mm, 14mm, and 26mm options - giving you a wide range of magnification choices for different targets.

Are these binoculars good for both astronomy and daytime use?

Yes. The BT-120 SF is explicitly designed for both astronomical and terrestrial observation. The 120mm aperture gathers tremendous light for night-sky viewing of the moon, planets, and deep-sky objects, while the wide field of view and sharp optics make it equally impressive for birding, wildlife watching, and scenic landscape viewing during the day.

What does IPX6 waterproof rating mean?

IPX6 means the binoculars are protected against powerful water jets from any direction - essentially rain, heavy splashing, and similar wet conditions will not damage the optics or internal components. The sealed, nitrogen-filled magnesium housing also prevents internal fogging when moving between temperature extremes, making the BT-120 SF suitable for use in genuinely demanding outdoor environments.

Can I use color or nebula filters with the BT-120 SF?

Yes. The 1.25" plug-in eyepiece system supports optional color and nebula filters, which can be threaded onto compatible eyepieces to enhance contrast on specific astronomical targets such as nebulae, planets, and the moon. These filters are sold separately.

Product specifications table
Specification name Specification Value
Color pattern White
Material Metal

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