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BT-120 SF Large Binoculars with 62 Degree LER Eyepieces

SKU 01-14230
BARCODE 00811803033955
Sold out
Original price $ 2,420.49 - Original price $ 2,420.49
Original price
$ 2,420.49
$ 2,420.49 - $ 2,420.49
Current price $ 2,420.49

All pricing in USD

Objective Diameter: 120mm


  • Powerful large binoculars with a 120 mm objective diameter and 660 mm focal length.
  • Observe the moon, the planets and bright deep sky objects in the night sky as well as terrestrial targets
  • Extremely robust binoculars, sealed and filled with nitrogen
  • Convenient 45-degree view and individual focusing
  • Carrying handle makes it easier to transport the binocular and ensures a secure hold during tripod assembly
  • Includes two premium waterproof Explore Scientific 62 degree 20mm LER eyepieces
  • Eyepiece holder 1.25 inch / 31.7mm, interchangeable eyepieces
  • Extendable dew caps minimize condensation on the lenses
  • Tripod connection: 2 x 1/4 inch and 1 x 3/8 inch photo thread
  • Optional accessories: Item 01-14300 U-mount with field tripod


Giant binocular for observing the starry sky, nature and landscape. 
Observe the beauty of the starry sky at night and distant objects in nature during the day. Globular star clusters, glowing gas nebulae, the moon with its craters and even planets can be observed wonderfully on a clear night. But also all other distant things in nature and landscape, even ships and airplanes can be seen in detail. With the all-round binoculars of the EXPLORE SCIENTIFIC BT series, you can get up very close. Thanks to the large, light-gathering lenses and the professional coatings on all lens surfaces, these binoculars produce bright and brilliant images even at night and at twilight, providing a special viewing pleasure. The comfortable 45 degree viewing angle allows fatigue-free use even when the binoculars are tilted strongly.  

A large binocular can also be called a double refractor telescope 
One complete lens telescope with the full light gathering power is available per eye. Experience a whole new dimension of observing. Objects are reproduced almost vividly in these binoculars and observing with both eyes is basically very relaxed. Last but not least, this comfortable way of observation increases the recognition of the finest details and effectively prevents rapid eye fatigue. 

Extremely robust binoculars with magnesium housing, sealed and filled with nitrogen  
The BT series binoculars are designed for tough outdoor use. The IPX6 sealed and nitrogen-filled design effectively prevents fogging of the internal optics even under difficult weather conditions. The very light magnesium housing saves weight and makes it easy to handle. Two EXPLORE SCIENTIFIC 20mm eyepieces of the 62 degree LER series already included. EXPLORE SCIENTIFIC is an established manufacturer of extremely high-quality eyepieces in the astronomy scene. An optical system is only as good as its weakest component. Therefore we have decided to deliver these giant binoculars with a pair of quality eyepieces of the 62 degree LER series. With an apparent field of view of 62 degrees and a focal length of 20mm, the BT-120 binoculars produce a 33x magnification. Thus these wide angle eyepieces offer a very good overview (field of view 1.8 degree) at moderate magnification. The large interpupillary distance of these LER (long eye relief) eyepieces of 15mm and soft silicone eyecups, which can be turned inside out, also guarantee a comfortable and relaxed view. For astronomy, a flat and sharp image field is advantageous and offers a particularly impressive viewing experience even during the day. Due to the waterproof design and the argon filling, these eyepieces are absolutely durable and easy to clean. 

Interchangeable eyepieces with 1.25 inch / 31.7mm plug-in diameter 
Adjust the magnification and field of view to your individual needs and choose from a wide range of available eyepieces. All eyepiece types with a plug-in diameter of 1.25 inch / 31.7mm can be used with the binoculars of the BT series. Especially recommended are EXPLORE SCIENTIFIC eyepieces of the 62 and 82 degree series with focal lengths from 8 to 26mm (see item No. 02188xx and 02196xx). The magnification can be varied from 25x to 75x (focal length binoculars: focal length eyepiece = magnification). The eyepieces are held in the binoculars by a precise brass compression ring clamp and guarantee a tilt free position.  

Use of color and nebula filters for astronomical observations 
Increase the contrast and visibility of objects and details by screwing the corresponding filters directly into the thread of the eyepiece sleeves. The use of color and nebula filters must of course always be done in pairs. Suitable are all EXPLORE SCIENTIFIC screw filters with 1.25inch / 31.7mm diameter (see item No. 03102xx)  

Comfortable 45 degree view and helical single focus 
The 45-degree viewing angle allows a relaxed observation position even when the binoculars are tilted strongly. Also the individual interpupillary distance can be adjusted in a range from 54 to 76mm. With the fine helical individual focusing, precise focusing is achieved effortlessly. Extendable dew caps The integrated dew caps can be removed in high humidity and cold conditions. This avoids fogging of the outer objective lenses and effectively shields additional control light coming in from the side. 

Integrated carrying handle 
A metal carrying handle located at the center of gravity facilitates transport and ensures a secure hold during tripod assembly. 

Suitable tripods and tripod connection
When using these large binoculars, a sturdy photo tripod with an appropriate load capacity is highly recommended. The connection is made via two 1/4 inch or one 3/8 inch threaded holes (standard photo tripod thread) in the tripod adapter of the binoculars. The ideal solution is to use the optional available EXPLORE SCIENTIFIC U-Mount with field tripod (item No. 01-14300). This is specially designed for the large binoculars of the BT series and carries these devices absolutely safely. The excellent mechanism with adjustable friction in both axis allows easy moving and tracking. The binocular position is kept stable depending on the adjusted friction intensity. Vibrations are reduced to a minimum by the massive construction of the U-Mount and the large stainless steel tripod. Even at high magnification there are no vibrations and the finest details can be observed.


My View on the Explore Scientific BT-120 SF Large Binoculars
- Andrew Corkill 10-15-22

I never thought I would be a big binocular user. That includes a binocular of any size. But as I live in a very light polluted area of Southern California, I realized that binoculars greatly help my ability to see the stars.

I’ve launched into a full-on exercise of using binoculars every day from 10x25 all the way to 25x100 in my backyard. The Explore Scientific BT-120 SF Large Binoculars are the largest bino’s I’ve used to date, and I bought them for a specific reason.

I found myself working through the Astronomical League Observing programs using binoculars to observe double stars, variable stars, open clusters, Messier objects, as well as the Moon and Planets. I worked through all these programs using binoculars of many different sizes, all the way up to 20x100’s. After enjoying so much observing with binoculars, I honed in on variable star observations as my nightly passion. I observe, estimate visual magnitude, and submit these observations to the American Association of Variable Star Observers (AAVSO).

As you can imagine, many variable stars are easily seen and can be visually estimated using the naked eye or binoculars. But there are many variable stars that can go from being very bright, greater than 2nd or 3rd magnitude at maximum, then fade all the way to 10th or 12th magnitude at minimum. In my light polluted backyard, when a star goes beyond 10th magnitude, it disappears in my 20x100 binoculars. At this point, I have to move to a larger telescope, or just stop observing that star. This shouldn’t be a problem, just stick to brighter variable stars. But, there are some variable stars that are just too interesting to pass up.

T Coronae Borealis (T CrB) is a variable star that is faint and out of sight. At least it’s out of sight from my backyard binoculars. I can “glimpse” it on a clear, transparent night with my 25x100 binoculars, but it needs to be at least 30 to 40 degrees above the horizon. T CrB is a Recurrent Nova, a star that goes through an incredible outburst of energy and light every 20 years or so. It can brighten from 10th magnitude all the way up to 2nd magnitude when it goes Nova. The next outburst should take place within the next 2 years (sometime in 2023 to 2024). Well, it’s time to measure and prep for this rare event, and I need more accurate ways to measure and see this star when it is fainter than 10th magnitude. The goal is to catch this star when it goes into “outburst” and increases in brightness in less than one night all the way up to 2nd magnitude. It’s time to go deeper and deeper into variable star observations. It’s time for the Explore Scientific BT-120 SF Large Binoculars.

The 120mm objectives of these binoculars, should give me the extra aperture I need to see this faint 10.0 to 11.0 faint magnitude star, T CrB. So after admiring these binoculars on the Explore Scientific website for a few weeks, I finally gathered the courage to ask my wife for a Holiday gift. And although this was the month of August, it seemed just right to me. I purchased the bino’s and they had their first light on Arcturus to get a sharp focus, and the next stop was T CrB.

The Binoculars are big, but lighter than they look. At 8300 grams (that’s 18.3 pounds to you and me) they are quite easy carry and lift onto the tripod. The binoculars came with the U-Mount with field tripod which were designed to work together. The motion is fluid and the binoculars are very easy to balance. They don’t lose their position when pointed at a distant object. Poetry in motion.

T CrB was shockingly easy to see in these binoculars (around 10.2 magnitude), and that is due to their large 120mm objectives. But remember that these binoculars come with 20mm eyepieces with a 62 degree FOV. This renders the sky into a beautiful observable circle of almost 2 degrees. What! This is awesome! With the 20mm eyepieces we are seeing these stars at 31x. Now you can imagine scanning the sky with a big 2 degree (1.96) Field of View and seeing everything magnified 31 times. T CrB and the impending Nova will be no match for these binoculars. I’ve found my trusted companion to watch nightly as we get closer to a very rare event of seeing this star go Nova.

I Highly recommend these binoculars and would not hesitate to encourage others to use both eyes while observing Planets, Star Clusters, Galaxies and other Deep Sky Objects. We have two eyes, and two halves of our brain deserve to get all the visual “stimulation” we can possibly give. You will have deepening experiences with Large Binoculars like these.

Just a note: I zoomed over to look at Jupiter, and found the Galilean Moons and Bands clearly visible. The bands were revealing their secret colors to these 120mm monsters while my brain devoured the details. Quickly to Saturn and WOW! The rings are incredible!

And now its time for the binoculars to go back in the box, they are a holiday gift remember, and my wife doesn’t forget. So this is my experience and my update for now. Still so much more to see with these amazing binoculars. I highly recommend them for anyone seeking to enjoy the universe from their backyard.


Item Number 01-14230
Optical design Achromatic refractor Porro
Mirror / lens diameter 120 mm
Focal length 660 mm
Focal ratio 5.5
Apparent Facial field 62 degrees
Type of remuneration Enhanced Multilayer Desposition (EMD)
Exit pupil min. 3.6 mm
Field of view 1.8 degrees
Waterproof Yes
Water resistance protection level IPX6
Exit pupil distance 15 mm
Total length 654 mm
Total width 290 mm
Total height 156 mm
Total net weight 8300 g
Housing material Magnesium


Explore Scientific offers free collimation service for the Giant Binoculars for the lifetime of the product. The customer is responsible for shipping both ways. Explore Scientific Giant Binoculars come with a 1-year warranty when registered within 60 days of purchase.

The Explore Alliance membership program offers Extended Care for all Explore Scientific products with a paid membership. For more information on the Explore Alliance Click Here 

Recommended Accessories: (2) Astrozap 5" Dew Heater Strap

CA Residents: Prop 65 WARNING(S)