*2nd* Orion BT70 Premium Binocular Telescope

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*2nd* Orion BT70 Premium Binocular Telescope

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Specs

Best for viewing

Brighter deep sky
Magnification

Magnification

A measure of the enlargement of an object seen through an optical instrument. More specifically, it is a measure of the angle subtended by an image viewed with optical aid divided by the angle subtended by the same object without optical aid. Magnification is determined by dividing the focal length of the telescope (or binocular) by that of the eyepiece. Hence a telescope with a 1200mm focal length and an eyepiece of 40mm yields a magnification of 30x. The human eye is considered 1x magnification.

20x
Optical diameter

Optical diameter

The optical diameter (also known as aperture), is the size of the telescope's main light collecting lens or mirror, measured in millimeters or inches. As the diameter increases, more light is collected and the resolution increases.

70mm
Field of view - angular

Field of view - angular

The field of view expressed as part of a 360-degree circle. Holding your pinky finger out at arms length is approximately 1-deg wide. To convert this to the linear measurement of "feet at a thousand yards", multiply by 52.5. For example, at 1000 yards distance, a 7-deg binocular will see a width of 367.5 feet (7 x 52.5)

3.0°
Field of view - linear

157.5 ft./1000 yd
Apparent field of view

Apparent field of view

The edge-to-edge angular diameter of the light emerging from the eyepiece as seen by the eye. It is an inherent specification for a given eyepiece type or design. The apparent field of view of an eyepiece is directly related to the true field of view seen through the telescope; for a given focal length eyepiece, the greater the eyepiece's apparent field of view, the greater area of sky will be seen.

63.0°
Eye relief

Eye relief

The distance, measured in millimeters, between the observer's eye and the eyepiece lens in which the entire field of view remains visible. Eye relief varies with the optical design but generally increases with decreasing magnification. Long eye relief is advantageous for observers who wear glasses, as they don't have to put their eye directly on the eyepiece to see the entire field of view, nor do they have to remove their eyewear.

15.5mm
Exit pupil

Exit pupil

The diameter of the circle of light exiting the telescope eyepiece. It appears as a distinct disk when the telescope is pointed at a bright source like the Moon. Also known as the Ramsden disk, the exit pupil varies with both aperture and magnification.

3.5mm
Near focus

Near focus

The minimal distance at which a binocular and/or spotting scopes can attain focus. Near focus is an important quality for bird watchers and wildlife devotees who want to get as close as possible to their quarry.

50 ft.
Coatings

Coatings

Lenses are coated with an antireflective material to ensure that as little light as possible is reflected away, so more gets to your eye. Good lenses are at least "fully coated," with a single layer of magnesium fluoride applied to each air-to-glass lens surface. Multiple layers of coatings are even more effective; the term "multi-coated" means one or more lens surfaces have multiple coatings. "Fully multi-coated" is even better, meaning that all lens surfaces are multiple-layer coated. Mirror star diagonals are coated with a reflective material similar to telescope mirrors in order to reflect the light into the eyepiece. Standard aluminum coatings reflect between 88%-92%, and enhanced aluminum reflects 97%. Dielectric coatings use a different process to deposit a coating that reflects 99% of the light. In addition to the higher reflectivity, Dielectric coatings are much more durable than aluminum coatings, so they last longer and can be cleaned with less risk of damage.

Coated
Prism

Prism

Porro Prisms: A binocular prism system that contains two right-angle prisms in each barrel offset from one another, requiring that the objective lenses be spaced further apart than the eyepieces. Optically, porro prisms often perform better than their roof prism counterparts. Roof Prisms: A compact binocular prism system that allows the objective lenses to line up directly with the eyepieces and hence yields a more portable binocular. Roof prism binoculars lose slightly more light to reflections than porro prism binoculars. High-quality roof prism binoculars compensate for this with special optical coatings.

BAK-4 Porro
Interpupillary distance range

Interpupillary distance range

The distance between the two pupils of an observer's eyes. Binoculars can be adjusted to accommodate variations in a person's interpupilary distance.

57mm - 74mm
Focus style

Individual eyepiece focus
Waterproof

No
Tripod adaptable

Yes
Diopter adjustment

Yes
Weight

8.9 lbs.
Height

12.2 in.
Additional included accessories

Other included items are not always the same between a new and a second. Seconds may be older versions of the new product, or may be customer returns where accessory substitutions have been made.
Other features

2nds are covered by Orion's Satisfaction Guarantee
Warranty

One year

Shipping Info

Orders received by noon Pacific Time for in-stock items ship the same business day. Orders received after noon will ship the next business day. When an item is not in-stock we will ship it as soon as it becomes available. Typically in-stock items will ship first and backordered items will follow as soon as they are available. You have the option in check out to request that your order ship complete, if you'd prefer.

A per-item shipping charge (in addition to the standard shipping and handling charge) applies to this product due to its size and weight. This charge varies based on the shipping method.

Standard Delivery: $0.00
3 Day Delivery: $43.00
2 Day Delivery: $43.00
Next Day Delivery: $53.00

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Since 1975 Orion Telescopes & Binoculars has been offering telescopes for sale direct to customers, with an unswerving commitment to best quality products, value and unmatched customer care. Our 100% satisfaction guarantee says it all.

Orion offers telescopes for every level: Beginner, Intermediate, Advanced, and Expert. From our entry level beginner telescopes for amateur astronomers to our Dobsonian telescopes to our most advanced Cassegrain telescopes and accessories, you can find the best telescope for you. And you'll enjoy discount prices by buying your telescope online, direct from Orion. Not sure how to choose a telescope? Orion's Telescope Buyer's Guide is a great place to start.

Orion binoculars are known for quality optics at a great price. We offer binoculars for every viewing interest, including astronomical binoculars, compact binoculars, waterproof binoculars, birding binoculars, and sport and hunting binoculars.

Orion's telescope and astrophotography accessories will enhance your telescope enjoyment without breaking the bank. Expand your viewing experience with accessories ranging from moon filters to power-boosting Barlow lenses to advanced computerized telescope mounts. Capture breathtaking photos with our affordable astrophotography cameras. And when you're stargazing, Orion's telescope cases and covers, observing gear, red LED flashlights, astronomy books and star charts will make your observing sessions more convenient, comfortable and meaningful.

At Orion, we are committed to sharing our knowledge and passion for astronomy and astrophotography with the amateur astronomy community. Visit the Orion Community Center for in-depth information on telescopes, binoculars, and astrophotography. You can find astrophotography "how to" tips and share your best astronomy pictures here. Submit astronomy articles, events, and reviews, and even become a featured Orion customer!