Telescope Size Ultimate Guide

This article covers a brief description of telescopes of 2-16 inches available on the market. Whether you want to buy a telescope for your kids or for astrophotography or just to view planets and galaxies, this article may guide you to the best option you are looking for. You will also be able to compare the focal lengths, focal ratios, price ranges, and magnifications among the telescopes of different apertures.

What is the best telescope size?

• For astrophotography: The ideal telescope for astrophotography would be a long focal length, large aperture, and color-corrected scope. These kinds of telescopes provide high-contrast views with details of the night sky objects. Telescopes with an 8-inch aperture or more are best for astrophotography.
• For beginners: Telescopes with 4 or 5 inches of aperture would be good for complete beginners as they are cheap and can show the planets of our solar system pretty well. When they will get an endeavor to know more about astronomy, they can upgrade their scopes to the next level.
• For kids: Telescopes with a 2-inch aperture and a 1.25-inch focuser are ideal for kids. They provide much better views than focusers with .965-inch eyepieces.
• To see planets: You should choose a scope at least with a 4-5 inch aperture to view the planets of our solar system and their moons. However, distant planets like Uranus and Neptune can be blurry and like dots of this size. Larger the aperture, the better the planetary views.
• To see galaxies: You need a telescope with a large aperture and good optical performance to see galaxies as they are distant deep night sky objects. The ideal scope to get clear views of them with details would have 8 inches or more aperture.

2-inch Telescopes

Photo of The Moon with a 2-2.75 inch telescope (cloudynights)

2-2.75 inch telescopes are considered to be in the category of a small telescope with an aperture of 50-70 mm. All 2-inch telescopes are basically for kids and beginners.

On average, they provide 360-900 mm focal lengths and a range of focal ratios from f/5.7-f/12.9. You can see Venus and its phases, the Moon with craters, Jupiter’s cloud bands, the Great Red Spot, Saturn with rings, M31 and M33, NGC galaxies, nebulae like M42, M8. 3-inch telescopes can magnify objects 122-165x times the human eye.

You can get 2-inch scopes from different brands in the price range of 85-730$. For example- Celestron AstroMaster 70AZ Telescope, Orion Observer II 60mm f/11.7 Doublet Refracting Telescope, Celestron Travel Scope 70, William Optics Gran Turismo 71, Orion StarBlast 62mm.

3-3.75 inch Telescopes

Photo of The Moon with a 3-3.75 inch telescope (reddit)

3-inch telescopes are ideal for kids and beginner astronomers with an aperture of 76-94 mm. On average, 3-inch telescopes provide 300-900 mm focal lengths and a range of focal ratios from f/3.9-f/12. They can magnify objects 152-189x times the human eye.

You can get 3-inch telescopes from different brands in the price range of 262-5200$. Three inch telescopes are in the category of small-size telescopes. You will be able to see the Moon with craters, Venus and its phases, Saturn with rings, Jupiter’s cloud bands, and the Great Red Spot, nearby galaxies like M31 and M33 and NGC galaxies, nebulae like M42, M8.

Examples of 3-inch telescopes: Celestron AstroMaster LT 76AZ Telescope, Orion SpaceProbe II 76mm f/9.2 Newtonian Reflecting Telescope, Celestron AstroMaster 80AZ Refractor, Explore Scientific FirstLight 80mm, Orion Grab-n-Go 80mm f/6 Triplet Refracting Telescope.

4-inch Telescopes

Photo of The Moon with a 4-inch telescope (littleastronomy)

4-inch telescopes are basically for amateur astronomers and kids with an aperture of 100-120 mm. They are great for viewing planets of our solar system too. On average, 4-inch telescopes provide 450-1350 mm focal lengths, and a range of focal ratios from f/3.9-f/9. They can magnify objects 204-236x times the human eye. They also can resolve double stars at 1.15 arcsec.

You can get 4-inch scopes from different brands in the price range of 262-5200$. 4-inch telescopes are in the category of small-size telescopes. You can see the Moon and its craters, the phases of Venus and Mercury, Mars’ polar ice caps, Jupiter’s cloud belts & the Great Red Spot, Saturn’s rings, the division in them, and several moons, Uranus and Neptune as dots, stars in the galaxies like in M13, M15, & M92, nebulae, such as M27, M57, the Cat’s Eye, NGC objects like M42, the Orion Nebula, and M8, the Lagoon Nebula.

For example: Takahashi FC-100DF f/7.4 Fluorite APO Refractor, Sky-Watcher StarTravel 102AZ3, Celestron AstroMaster 114EQ Telescope, Takahashi FSQ-106EDX4 f/5, Celestron Nexstar 4SE GoTo Telescope.

5-inch Telescopes

Photo of The Moon with a 5-inch telescope (littleastronomy)

5-inch telescopes are basically for kids and amateur astronomers with an aperture of 127-130 mm. They can be used for planetary views. On average, 5-inch telescopes provide 650-1900 mm focal lengths, and a range of focal ratios from f/5-f/15. They can magnify objects 225-260x times the human eye. They also can resolve double stars at 0.91 arcsec.

You can get 5-inch scopes from different brands in the price range of 279-8400$. A 5-inch telescope is considered to be in the category of a medium telescope. You will be able to see the Moon and its craters, the phases of Venus and Mercury, the cloud belts of Jupiter and Great Red Spot, the Cassini Division in Saturn’s rings, Uranus and Neptune as bluish dots, brightest nebulae and star clusters like M42, M27, and M13.

For example: Explore Scientific 127mm Air-Spaced ED APO f/7.5 Triplet Refracting OTA, Celestron StarSense Explorer DX 130AZ, Sky-Watcher Skymax 127 AZ-GTi f/12.1 Maksutov Cassegrain, Celestron NexStar 5SE Computerized Telescope.

6-inch Telescopes

Photo of The Moon with a 6-inch telescope ( shutterstock)

6-inch telescopes are basically for amateurs with an aperture of 150 mm. A 6-inch telescope is considered to be in the category of a medium telescope. They are great for planetary views. On average, 6-inch telescopes provide 162-1800 mm focal lengths, and a range of focal ratios from f/3.9-f/10. They can magnify objects 295-320x times the human eye. They also can resolve double stars at 0.76 arcsec.

You can get 6-inch telescopes from different brands in the price range of 310$ – 15,070$. You will be able to see the Moon and its craters, Jupiter with its cloud belts, the Great Red Spot, Saturn and its bands, the Cassini Division, Uranus and Neptune, Galaxies like M83, Whirlpool Galaxy, M81 and M82, globular star clusters like M5, M13, M15, and M92, nebulae like NGC 7027 in Cygnus. 

For example: Sky-Watcher Esprit 150mm ED Triplet APO Refractor, Celestron Advanced VX 6″ Refractor Telescope, Sky-Watcher 150mm Maksutov Cassegrain, TPO 6″ f/9 Ritchey Chretien Reflecting OTA Telescope, Orion SkyQuest XT6 Classic Dobsonian, Meade 6″ f/10 LX85 ACF, Celestron Omni XLT 150 Telescope.

7-inch Telescopes

Photo of The Moon with a 7-inch telescope (astrobin)

7-inch telescopes are basically for amateurs though there are some advanced scopes for professional astronomers with this aperture (180 mm). Overall, 7-inch telescopes provide 500-2700 mm focal lengths, and a range of focal ratios from f/2.8-f/15. They can magnify objects 356 times the human eye. They also can resolve double stars at 0.65 arcsec.

You can get 7-inch scopes from different brands in the price range of 1350-5500$. A 7-inch telescope is considered to be in the category of a medium telescope. You will be able to see the Moon and its craters, Jupiter with its cloud belts, the Great Red Spot, Saturn and its bands, the Cassini Division, Uranus and Neptune, galaxies like M83, Whirlpool Galaxy, M81 and M82, globular star clusters like M5, M13, M15, and M92, nebulae like NGC 7027 in Cygnus. 

For example: Takahashi Mewlon 180 C· f/ 12 Dall Kirkham Reflecting Telescope, Sky-Watcher 180mm Maksutov Cassegrain, Celestron CGX 700 Maksutov Cassegrain Telescope,, Celestron Advanced VX 700, Sky-Watcher 190mm Maksutov-Newtonian Telescope OTA.

8-inch Telescopes

Photo of The Moon with an 8-inch telescope (astrobin)

8-inch telescopes are basically for entry-level astronomers. They are great for viewing planets and galaxies and even for astrophotography. Overall, 8-inch telescopes provide 800-2415 mm focal lengths, and a range of focal ratios from f/4-f/11.5. They offer twice the light-gathering power of a 4-inch telescope. 8-inch telescopes allow magnification up to 300-480x.

You can get 8-inch scopes from different brands in the price range of 1899-8,320$. An 8-inch telescope is considered to be in the category of a medium telescope. You will be able to see the Moon and its craters, Jupiter with its cloud belts, and the Great Red Spot, Jupiter’s moons in ruddy orange-yellow color, Saturn and its bands, the Cassini Division, and its largest moon-Titan., Uranus and Neptune are as an azure disk, galaxies like M74 and M83, Whirlpool Galaxy, M51 B/NGC 5195, M81 and M82 in Ursa Major, the Virgo Cluster, globular star clusters like M2, M3, M5, M13, M15, and M92, nebulae like the Ring and Dumbbell, the Blinking Planetary Nebula, and NGC 7027 in Cygnus.

For example: Orion 8″ f/8 Ritchey Chretien Reflecting OTA Telescope, Orion SkyQuest XT8 Classic Dobsonian, Celestron Advanced VX 8″ Schmidt-Cassegrain, Meade 8″ f/4 LX85 Astrograph Reflector, Orion 8″ f/4 Newtonian Reflector Astrograph, Celestron RASA 8″ Telescope, Meade LX200-ACF 8″.

9.25-inch Telescopes

Photo of The Moon with a 9.25-inch telescope (astrobin)

9.25-inch telescopes are for amateur and hobbyist astronomers. They are great for astrophotography, and planetary views. On average, 9.25-inch telescopes have 2350-2500 mm focal lengths, and a focal ratio of f/10. They provide 33% more than the light-gathering power of an 8-inch telescope. Only the Celestron brand offers different types of 9.25 inch-telescopes.

You can get 9.25-inch scopes in the price range of 1899-8,320$. A 9.25-inch telescope is considered to be in the category of a medium telescope. You can see the Moon and its craters, the phases of Venus and Mercury, Mars and its ice cap, Jupiter’s cloud belts and the Giant Red Spot, Saturn’s rings and the Cassini Division, Uranus & Neptune as dots., galaxies like M82 and M31, Nebulae like Orion or the Lagoon.

For example: Celestron CGX-L Equatorial 9.25″ EdgeHD, Celestron NexStar Evolution 9.25″ Computerized Telescope, Takahashi Mewlon 250CRS w/ Built-In Corrector & Active Focus, Celestron 9.25″ EdgeHD OTA.

10-inch Telescopes

Photo of The Moon with a 10-inch telescope (staticflickr)

10-inch telescopes are basically for amateur and hobbyist astronomers with an aperture of 254 mm. On average, 10-inch telescopes have 1000-2500 mm focal lengths, and f/3.9-f/10 focal ratios. They provide six times the light-gathering power of a 4-inch telescope and four times the light-gathering power of a 5-inch telescope.

You can get 10-inch scopes from different brands in the price range of 630-10,000 $. They are great for astrophotography too. A 10-inch telescope is considered to be in the category of a medium telescope. You will be able to see the Moon and its craters, the phases of Venus and Mercury, Mercury’s small disk, Mars and its ice cap, and outer moon Deimos, Jupiter’s cloud belts, the 4 largest moons of Jupiter- the Galilean moons Io, Europa, Ganymede, and Callisto, Saturn’s rings and the Cassini Division along with some cloud bands on Saturn and half a dozen of its moons, Uranus with the moons- Oberon and Titania, Neptune with its moon Triton, the spiral arms of brighter galaxies like M51 and M33.

For example: Celestron Starsense Explorer 10″ Dobsonian, Meade 10″ ACF LX90m, Sky-Watcher Flextube 250P f/4.7 Dobsonian, TPO 10″ f/8 Ritchey Chretien Reflecting OTA Telescope, AG Optical 10″ iDK f/6.7 Imaging Dall Kirkham.

11-inch Telescopes

Photo of The Moon with an 11-inch telescope (Source: istockphoto)

11-inch telescopes allow observers to see stars of 16 magnitudes. They can resolve double stars at 0.42 arcseconds. On average, 11-inch telescopes have 620-2800 mm focal lengths, and f/2.2-f/10 focal ratios. They provide magnification power 304x times the human eye. They vary in light-gathering power from 1589-1593x. Overall, they offer outstanding optical performance. They are amazing for astrophotography as they provide great details of planets and galaxies. 

An 11-inch telescope is considered to be in the category of large telescopes with an aperture of 279 mm. Only Celestron brands make different types of 11-inch telescopes. You will be able to see the Moon and its craters, the polar ice caps on Mars, the phases of Venus, the moons of Jupiter, the Great Red Spot, and other details, the rings of Saturn and the Cassini Division, Uranus and Neptune, galaxies like Andromeda, M81, and the NGC galaxies.

For example: Celestron C· 11 SCT, Celestron 11″ Schmidt-Cassegrain CGX Telescope, Celestron 11″ EdgeHD OTA, Celestron CGX with 11″ RASA V2 – CE-12060.

12-inch Telescopes

Photo of The Moon with a 12-inch telescope (telescopeboss)

12-inch telescopes allow observers to see stars of 16.2 magnitudes. On average, 12-inch telescopes have 1200- 1525 mm focal lengths, and f/3.93-f/5 focal ratios. They can resolve double stars at 0.38 arcsec. They provide magnification power 600x times the human eye. They are great for astrophotography as they provide great views of planets and galaxies with details. They have an aperture of 305 mm.

A 12-inch telescope is considered to be in the category of large telescopes. You will be able to see the Moon and its crater Copernicus and volcanic plains around it, the rings of Saturn and the Cassini Division, the phases of Venus, the moons of Jupiter, the Great Red Spot, and other details, the polar ice caps on Mars, Uranus and Neptune, 5000 star-clusters like M3, M5, and M13, 3000 nebulae like Ring, Dumbbell, and Swan nebulas, 22000 galaxies like M81 or the Leo Triplet, the Whirlpool and the NGC galaxies.

For example: Sky-Watcher 12″ f/3.93 Quattro Imaging Newtonian Telescope, Sky-Watcher Flextube 300P SynScan 12″ f/4.9 Dobsonian, Explore Scientific 12″ f/5 Truss Tube Dobsonian.

14-inch Telescopes

Photo of The Moon with a 14-inch telescope (skyandtelescope)

14-inch telescopes offer clarity, contrast, and a flat field of view. They are great for astrophotography as they provide great views of planets and galaxies with details. On average, 14-inch telescopes have more than 2500x light gathering power, 2463-3916 mm focal lengths, and f/6.7-f/11 focal ratios. They offer exceptional resolutions for their size and can resolve double stars at 0.22 arcsec. They have an aperture of 355 mm.

A 14-inch telescope is considered to be in the category of large telescopes. You will be able to see the Moon and craters with precise details, the planets of our solar system, the galaxies like M33 (the Triangulum Galaxy), M13 (the Great Hercules Cluster), NGC 6946 (spiral· galaxy in Cepheus), NGC 7380 (nebulous cluster in Cepheus), and IC 5070 (the Pelican Nebula).

For example: Meade 14″ ACF LX200, PlaneWave CDK350 (14-inch) Telescope, AG Optical 14.5″ iDK f/6.7 Imaging Dall Kirkham, TPO 14″ f/8 Ritchey Chretien Truss Tube, Celestron 14″ CGE Schmidt-Cassegrain OTA.

15-inch Telescopes

Photo of The Moon with a 15-inch telescope (obsessiontelescopes)

A 15-inch aperture offers a light-gathering power 4 times that of an 8-inch Schmidt-Cassegrain telescope. Amateurs will get amazing detailed views of the deep night sky objects with it. Obscure galaxies will appear with real color and details. However, there are not many options for a 15-inch telescopes available on the market. Obsession Ultra Compact (UC) 15-inch Dobsonian is the only scope with a 15-inch (381 mm) aperture. It is great for astrophotography and serious astronomy.

A 15-inch telescope is considered to be in the category of large telescopes. You will be able to see the Moon and craters with clear details, the phases of Venus, the moons of Jupiter, the Great Red Spot, the Cassini Division, the polar ice caps on Mars, the rings of Saturn, Uranus, and Neptune with their bluish color, the galaxies in Virgo Cluster or Ursa Major.

16-inch Telescopes

Photo of The Moon with a 16-inch telescope (ytimg)

A 16-inch telescope is one of the largest telescopes for amateurs and hobbyist sky gazers. The large aperture can gather a large amount of light, making the views of planets and other night sky objects sharp. Serious astronomers and astrophotographers also prefer this scope for the amazing views and optical performance. The magnification allows them to research the details of distant galaxies and star clusters. The light-gathering power is 4 times the 8-inch telescope and 16 times the 4-inch telescope. This is the best portable telescope for astrophotography used by novice astronomers.

All 16-inch telescopes are considered to be in the category of large telescopes. You will be able to see the Moon with clear details like craters, galaxies like M82 or the Cigar Galaxy with its dust lane, the phases of Venus, the moons of Jupiter, the polar ice caps on Mars, the rings of Saturn, Uranus and Neptune with their bluish color, Orion with blue and purple color and details, Star Clusters like M13 and the Hercules Globular Cluster.

For example: Sky-Watcher 16″ GoTo Collapsible Dobsonian, TPO 16″ Truss Tube f/8 Ritchey Chretien Reflecting OTA Telescope, Meade LX200-ACF 16″ UHTC OTA, Meade LX600 16″ F/8 ACF Optical Tube Assembly, Explore Scientific 16″ Truss Tube Dobsonian- F/4.5.