A telescope (from the Greek τηλε (tele) meaning “far” and σκοπεῖν (skopein) meaning “look, see”) is an optical instrument that increases the brightness and apparent size of the objects to be observed. Its role as a light receiver is often more important than its optical magnification, it allows to see punctual celestial objects that are difficult to perceive or invisible to the naked eye.
Telescopes are mainly used in astronomy because their settings only make them suitable for observing objects far away and moving relatively slowly.
There are two major types of telescopes, depending on how the light is focused by the lens:
In a refracting telescope the light is focused by a dioptric system composed of a set of lenses (refraction);
In a reflecting telescope light is focused by a catadioptric system composed of mirrors (reflection) but also diopters (e. g. correctors).
History of the telescope
The telescope’s precursor would have been designed in Italy around 1586 most probably by the Italian optician Giambattista della Porta, or perhaps as early as around 1550 by Leonard Digges.
The telescope appeared in Holland where the States General of 1608 successively received Hans Lippershey’s patent application on October 2 and a few weeks later Jacob Metius’; the magnification factor of these telescopes was 3 to 4. Very quickly used for multiple purposes, in particular as an astronomical telescope, the telescope interested the Italian astronomer Galileo who obtained a copy probably during the visit in 1609 of a Dutch merchant who came to propose the object to the Serenissima, then Galileo perfected the model, increasing its magnification by a factor of 2 to 3. At the top of the bell tower, he caused a sensation by offering an astronomical telescope of his own making to Doge Leonardo Donato and the members of the Senate. His German colleague Johannes Kepler perfected the principle, by proposing an optical formula with two convex lenses.
In a telescope, a concave mirror is used to form the image. In 1663, the Scottish mathematician James Gregory was the first to propose the telescope formula with a secondary magnification. Nevertheless, Marin Mersenne had anticipated a system in which the primary and secondary were parabolic, the exit pupil was located on the secondary, which thus served as an eyepiece. But the field was very weak.
The English mathematician and physicist Isaac Newton built a first version in 1668. In this type of instrument, the light reflected from the concave primary mirror must be brought to an observation position, either under or to the side of the instrument. Henry Draper, one of the very first American astronomers to build a telescope, used a full reflection prism two centuries later instead of the plane mirror of the Newton telescope.
The pioneer was the 2.53-metre telescope at the Mount Wilson Observatory in California, which remained famous for its use in the 1920s for the work of the American astronomer Edwin Hubble, and was discontinued under financial pressure from 1985 to 1992.
The design of the Keck telescopes marks an important innovation: the reflective surface of the mirror of each of the two telescopes is composed of a mosaic of thirty-six hexagonal mirrors, all of which can be individually adjusted using three cylinders. It is equivalent to a primary mirror 10 m in diameter, without having the weight. Active optics techniques are used to play on the cylinders to optimize the profile of the total reflective surface.
The Very Large Telescope (VLT) of the European Southern Observatory (ESO), on the other hand, consists of four telescopes, each with an 8.20 m mirror. It is located in Chile, at the top of Cerro Paranal, at an altitude of 2,600 m. In 2002, it was equipped with the NAOS adaptive optics system, enabling it to be twice as accurate as the Hubble Space Telescope.
It is also possible today to use the principles of interferometry in the optical domain to improve resolution. This is the principle used by the two Kecks, but especially by the VLT whose four mirrors, maximum 130 m apart, have the same theoretical resolution as a single mirror 130 m in diameter. However, the sensitivity is not improved, and the interferometry technique remains quite special, often used in very special cases.
Bestselling Telescopes
Celestron - 70mm Travel Scope - Portable Refractor Telescope - Fully-Coated Glass Optics - Ideal Telescope for Beginners - BONUS Astronomy Software Package
- Superior optics: The Celestron 70mm Travel Scope features high-quality, fully-coated glass optics, a potent 70mm objective lens, a lightweight frame, and a custom backpack to carry it all. Its quality is unmatched in its class and against competitors.
- Powerful eyepieces for up-close viewing: Our telescope for astronomy beginners is equipped with two high-quality eyepieces (20mm and 10mm) that provide low- and high-power views of celestial objects at night and terrestrial objects during the day.
- Large 70mm objective lens: Our refractor telescope is equipped with a large 70mm aperture objective lens that provides enhanced, brighter views compared to the 50mm model while adding very little additional weight. Setting up and using the Travel Scope is quick and easy.
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- Unbeatable warranty and customer support: Buy with confidence from the telescope brand, based in California since 1960. You’ll also receive a 2-year warranty and unlimited access to technical support from our team of US-based experts.
TELMU Telescope, 70mm Aperture 400mm AZ Mount Astronomical Refracting Telescope Adjustable(17.7In-35.4In) Portable Travel Telescopes with Backpack, Phone Adapter
- 【High Quality Optics】400mm(f/5.7) focal length and 70mm aperture, fully coated optics glass lens create stunning images and protect your eyes. Perfect telescope for astronomers to explore stars and moon.
- 【High Magnification】Come with two replaceable 1.25" Kellner eyepieces(K6mm/67X, K25/16X) ，5x24 finderscope with mounting bracket and cross-hair lines inside make locating objects easily.
- 【Satisfaction Warranty】 2-year warranty and lifetime maintenance. If you have any question about product and service, please feel free to contact us, we will do our best to help you.
- 【EASY TO OPERATION】 No tools are required for refractor telescope even for the novice. Adjusted from about 17.7-inch to 35.4-inch. Allowed for many different observational positions and keep the whole tripod steady with castor wheel.
- 【SHARING IN REAL TIME】You can take pictures or videos and share them with your family and friends in real time with the phone holder. Star telescope is suitable for kids who love science to discover the mystery of universe.
Celestron - PowerSeeker 127EQ Telescope - Manual German Equatorial Telescope for Beginners - Compact and Portable - Bonus Astronomy Software Package - 127mm Aperture
- Perfect entry-level telescope: The Celestron PowerSeeker 127EQ is an easy-to-use and powerful telescope. The PowerSeeker series is designed to give the new telescope user the perfect combination of quality, value, features, and power
- Manual German equatorial mount: Navigate the sky with our Newtonian Reflector telescope. It features a German Equatorial mount with a slow-motion altitude rod for smooth and accurate pointing. Adjust rod to desired position, then easily secure by tightening cross knob
- Compact and portable: This telescope for adults and kids to be used together is compact, lightweight, and portable. Take the telescope to your favorite campsite or dark sky observing site, or simply the backyard. Optical Coatings: Aluminum
- Multiple accessories: The Celestron PowerSeeker 127EQ Telescope comes with 2 eyepieces (20mm and 4mm), plus a 3x Barlow lens to triple the power of each. Users can also download BONUS Starry Night Astronomy Software Package
- Unbeatable and customer support: Buy with confidence from the telescope brand, based in California since 1960. You’ll also receive a 2-year and unlimited access to technical support from our team of US-based experts
Celestron - AstroMaster 70AZ Telescope - Refractor Telescope - Fully Coated Glass Optics - Adjustable Height Tripod – BONUS Astronomy Software Package
- POWERFUL REFRACTOR TELESCOPE: The Celestron AstroMaster 70AZ is a powerful and user-friendly refractor telescope with fully coated glass optics, a sturdy yet lightweight frame, two eyepieces, a red dot finder scope, and an adjustable-height tripod.
- HIGH-QUALITY 70MM OPTICS: Our Celestron telescope features a powerful, fully coated 70mm glass optic objective lens. Erect image optics allow you to observe celestial objects at night and terrestrial targets like wildlife and landscapes during the day.
- QUICK SETUP & LIGHTWEIGHT FRAME: This telescope for adults features a lightweight frame and a panning handle with Alt-Az control for smooth and accurate pointing. Setup is quick and easy, with no tools required.
- INCLUDED ACCESSORIES: We’ve included two eyepieces (20mm and 10mm), an erect image star diagonal, a travel tripod, and a red dot finder scope. Download our BONUS Starry Night Basic Edition astronomy software for interactive sky simulation.
- UNBEATABLE WARRANTY AND CUSTOMER SUPPORT: Buy with confidence from the world’s #1 telescope brand, based in California since 1960. You’ll also receive a 2-year warranty and unlimited access to technical support from our team of US-based experts.
NASA Lunar Telescope for Kids – Capable of 90x Magnification, Includes Two Eyepieces, Tabletop Tripod, Finder Scope, and Full-Color Learning Guide, the Perfect STEM Gift for a Young Astronomer
- INSPIRE CURIOSITY – The NASA Lunar Telescope allows your child to see the moon in incredible detail; the perfect gift for girls and boys interested in space, the moon, and astronomy
- HIGH-QUALITY OPTICAL GLASS AND FINDER SCOPE – This easy-to-use telescope comes with a finder scope, low power, and high-power eyepieces; when used correctly, this combination will allow your child to easily locate the moon and then zoom in for a close-up view
- TABLETOP TRIPOD – Use the included tripod to steady your Lunar Telescope for optimal viewing
- PERFECT FOR BEGINNERS – This telescope is easy to assemble and use, making it ideal for young scientists and parents to enjoy together
- 100% SATISFACTION GUARANTEE - You and your child will love this Lunar Telescope! We take pride in the quality of our products and our mission to inspire a child’s natural love of science. If you or your child had a negative experience with one of our products, we want to know so we can make it right.
Monocular Telescope - 12X50 High Definition FMC BAK4 HD Monocular 【Day & Low Night Vision】 with Smartphone Holder & Tripod IPX7 Waterproof & Eco-Friendly Materials for Bird Watching, Camping (Black)
- 【12X50 Monocular for Incredible Clear Vision】-- Equipped with A full 12x magnification and 50mm object lens diameter monocular, provides a clearly and bright image, enjoy the beauty of the distance. slopehill monocular telescope has a large field of view (360ft 1,000Yds), bring you the best view in your outdoor adventures, just feel free to enjoy bird watching, hunting, hiking, camping, travelling, wildlife, scenery, etc.
- 【High Contrast and Resolution Images】-- Newest optics technology, the HD monocular telescope equipped with BAK-4 prism and fully muti-coated lens, guarantee superior light transmission and brightness and the light transmittance reaches up to 99.5%. Our monocular has low-light-level night vision, it can help you see things in low light (can't see anything in complete darkness), provide you amazing viewing experience.
- 【Single Hand Focus, Waterproof & Fog Proof】-- Ergonomic design helps you focus on your target quickly and accurately with one hand. And the durable rubber armor with stripes makes it comfortable for use, non-slip grip, and durable external protection from your hand. IPX7 Nitrogen-Filled Waterproof with a fog-resistant coating and O-ring sealed optics prevent moisture, dust and debris to keep it clear all the time.
- 【Monocular Widely Compatible for Smartphone】-- Comes with a 2020 newest quick alignment smartphone holder and tripods. Perfect for iPhone XS Max/XR/XS/X/ iPhone 8/8 plus, 7/7 plus, 6/6s plus, Samsung GALAXY S9/S9 Edge, S8/S8 Edge, S7/S7 Edge, LG, HTV, Sony, and almost all other smartphones on the market. Easy to install, provide HD image or video to share with your friends.
- 【What You Get】 -- 1*HD Monocular Telescope, 1*Phone Adapter, 1*Adjustable Metal Tripod, 1*Lens Covers, 1*Hand Strap, 1*Cloth Bag, 1*Cleaning Cloth and 1*User Manual. You can use it for travel or send it to your family / friends as a gift. We Provide 30 days money free back, 1-Year seller support and lifetime dedicating email service to assure your long-term enjoyment.
MaxUSee Kids Telescope 400x40mm with Tripod & Finder Scope, Portable Telescope for Kids & Beginners, Travel Scope with Moon Mirror, Stars & Moon map Included
- Portable Telescope that easy to use and suitable for Kids & Beginners, High Quality Optics make your view brighter, clearer and delivers crisp images.
- Focal length 400mm Refractor telescope with 5X18 finder scope makes locating objects easy and fast.
- Includes two interchangeable eyepieces H12.5mm & 20mm, comes with a Moon mirror & Compass built-in the telescope tube.
- Easy assembly and quick start guide, Stars map & Moon map included.
- Educational Science Telescope that brings lots of fun and joy to Children.
Meade Instruments 209001 Infinity 50mm AZ Refractor Telescope
- Aperture: 50mm(2"). focal length: 600mm. Focal Ratio: f/12. Rack-and-pinion Focuser
- Altazimuth mount makes pointing the telescope easy
- Low (20mm), medium (12mm), high (4mm) magnification eyepieces give you variety for any viewing situation & 2x Barlow lens doubles the magnifying power of each eyepiece
- 5x24 optical Viewfinder helps you point your scope at objects you want to observe & accessory tray stores accessories while observing
- Includes astronomical software and instructional DVD
ToyerBee Telescope 76mm Aperture 700MM, with 3 Eyepieces H20mm H12.5mm H4mm&Tripod&Finder Scope&Moon Mirror, 70X-350X Magnification- Reflector Telescope for Kids& Students&Adults&Astronomy Beginners
- ✔High Magnification. ToyerBee telescope is equipped with three eyepieces (H20mm, H12.5mm and H4mm) and a 2X Barlow lens. The Barlow lens doubles the magnification of each eyepiece. Kids can get magnification of 35X to 350X. Whether it's watching stars and moons at night or observing planets, ToyerBee telescope is the best helper for kids & astronomy beginners.
- ✔Quick to find the view. Focal length 700mm with a finder scope help you to locate the object quickly. A solid & adjustable tripod which can be used on most surfaces can stabilizes the telescope when you focus. Whether you want to see the moon in the distance or the trees across the road, the telescope can help you quickly target.
- ✔Large aperture. 76mm aperture provides more lights and clearer images, even beginners can get clear images. The bigger the aperture, the bigger the field of vision, and the clearer the image. Imagine that the moon at night is as clear and bright as the scenery during the day.
- ✔Easy to assemble& dismount. We have a full set of paper and video Installation Guidelines. Don't worry about any installation problems. Even for first-time users, children can install it themselves without any tools.
- ✔ Satisfaction Warranty. 3-year guarantee was offered by ToyerBee. Please feel free to contact us if you have any questions about our telescope and service.
MaxUSee 70mm Refractor Telescope with Tripod & Finder Scope, Portable Telescope for Kids & Astronomy Beginners, Travel Scope with 4 Magnification eyepieces & Phone Adapter
- Portable telescope with wide range of different magnification from 16X to 200X, the perfect First Telescope for kids & astronomy beginners.
- 70mm Large aperture objective lens make the images brighter and clearer, with 5X24 finder scope can locate objects faster and earlier.
- Includes 4pcs 1.25" eyepieces H6mm, H12.5mm, H20mm and K25mm. High magnification (H6mm), middle magnification (H12.5mm) and low magnification but with sharper image (H20mm & K25mm) eyepieces give you variety for any viewing situation.
- Focal length 400mm refractor telescope comes with a durable Table-top tripod, includes the accessories 3X Barlow lens, 1.5X Erecting eyepiece and Moon mirror.
- Travel scope that Easy to carry & Quick to set up - Comes with a phone adapter that you can use cell phone for video camera and image capturer.
