2-inch Telescopes (50-70mm)

What is a 2-inch telescope?

A 2-inch telescope is a type of refracting or reflecting telescope that is used for both terrestrial applications and astronomy. The 2-inch measurement refers to the diameter of the telescope’s main optical component, which is either an objective lens or a primary mirror. The significance of the aperture in a 2-inch telescope lies in its ability to collect light and determine the resolution of the images produced. A larger aperture allows for greater light-gathering power and higher resolution, which can result in brighter and more detailed views of celestial objects. The focal length in relation to a 2-inch telescope is significant because it determines the magnification and angle of view. A longer focal length results in higher magnification but a narrower field of view, while a shorter focal length provides a wider field of view but lower magnification. The purpose of a finder scope on a 2-inch telescope is to help locate and aim the telescope at specific objects in the sky, providing a wider field of view and aiding in alignment with specific targets in the night sky. The purpose of eyepieces in a 2-inch telescope is to magnify and refine the image produced by the telescope’s primary optics, allowing for detailed celestial observation and varying levels of magnification. Objective lenses and eyepiece lenses are used in the optical design of a 2-inch telescope. The combination of these lenses determines the telescope’s focal length, magnification, and field of view. A 2-inch telescope typically has either an Altazimuth mount or an Equatorial mount. The purpose of the mount is to provide stability and precise control of the telescope’s movements, allowing for tracking and alignment with celestial objects. The purpose of the tripod in a 2-inch telescope is to provide stability and support for the telescope, allowing for more precise and steady observations. Common accessories for a 2-inch telescope include 2-inch eyepieces, padded telescope cases, carry bags, aluminum cases, and storage options such as fishing tackle boxes, tool boxes, backpacks, or bins. The advantages of a 2-inch eyepiece over a 1.25-inch eyepiece, such as a wider field of view and brighter images, can also apply to a 2-inch telescope. Some examples of respected 2-inch telescope eyepieces include Explore Scientific’s 82° series, Tele Vue Ethos models, Tele Vue Nagler eyepieces, and Baader’s Hyperion range. These can enhance the viewing experience of a 2-inch telescope.

What is a 2-inch refractor telescope?

A 2-inch refractor telescope is a type of telescope that uses a lens as its objective to form an image. It is portable due to its compact size, lightweight design, and straightforward focal length. The primary purpose of a 2-inch refractor telescope is for astronomical observations and terrestrial applications. The aperture of the telescope, which is the size of the objective lens, is 2 inches, and it has a maximum recommended magnification of around 100x to 120x. The focal length of a 2-inch refractor telescope plays a significant role in determining its magnification power. It can be used to observe celestial objects such as planets, stars, and galaxies, making it a suitable option for beginners in astronomy. An equatorial mount is typically used for a 2-inch refractor telescope to provide stability and support for steady viewing and tracking of celestial objects.

What is a 2-inch reflector telescope?

A 2-inch reflector telescope is a type of telescope that uses a primary mirror with a diameter of 2 inches to gather and focus light. The telescope’s aperture, which refers to the size of the primary mirror or lens, is 2 inches. This is a crucial factor as a larger aperture allows for a brighter image. The design of a reflector telescope includes a primary mirror located at the opposite end of the telescope from the aperture and a smaller secondary mirror near where the reflected light converges. Reflector telescopes, like the 2-inch version, are often less expensive than refractors since manufacturing large mirrors is usually more affordable than manufacturing large lenses. The type of focuser used in the telescope (e.g., a Crayford focuser) can significantly affect the user’s experience, particularly for astrophotography. The image viewed through a reflector’s eyepiece will be upside down by default. Therefore, a finderscope or a red dot finder is typically used to line up the telescope with the objects you want to see before looking through the eyepiece. The magnification of a 2-inch reflector telescope can be easily changed by switching the eyepiece. A magnification of 50X is plenty of power to see various celestial objects.

What can you see with a 2-inch telescope?

A 2-inch telescope is a versatile instrument that allows for the observation of a variety of celestial objects, making it ideal for kids and beginners. With an average focal length between 360-900 mm and a range of focal ratios from f/5.7-f/12.9, a 2-inch telescope is a great tool for exploring the night sky.
With a 2-inch telescope, you can expect to see celestial objects like the Sun (with a filter), planets, and some details of deep-sky objects like nebulae and galaxies under dark sky conditions.
The specific types of deep-sky objects that can be observed using a 2-inch telescope under dark sky conditions include galaxies, nebulae, and star clusters. Some examples of specific celestial objects that can be observed with a 2-inch telescope include the Andromeda Galaxy, Orion Nebula, and Pleiades Star Cluster.
The observing experience with a 2-inch telescope can be affected by atmospheric conditions and light pollution. The clearer the sky and the darker the location, the better the views will be.
It is important to note that the observer’s eyesight and experience also play a role in determining what can be seen with a 2-inch telescope. The above-mentioned objects are visible with a 2-inch telescope, but the level of detail and the ability to see fainter objects may vary from person to person.

Types and Technical Specifications of 2-inch telescope

Types (Optical Design)

Solar: Example: Orion 70mm White-Light f/7.1 Solar OTA Telescope.

Petzval: Example: William Optics RedCat 51II – Upgraded Version, William Optics RedCat 71 APO Telescope – Red,  Orion StarBlast 62mm Compact Travel f/8.4 Quadruplet Refracting OTA Telescope.

Triplet Refractor: Example: William Optics Gran Turismo 71 APO Refractor with Flattener, Radian 61 f/4.5 Imaging APO Telescope, William Optics Gran Turismo 71 APO Refractor – Red, Sharpstar 61EDPH II f/5.5 Triplet APO Refractor Telescope

Doublet Refractor: Example: Celestron Travel Scope 70 DX f/5.7 Portable Refractor Telescope with Backpack, Orion ED66 CF f/6.1 Doublet Refracting Telescope, Orion Observer II 70mm f/10 Doublet Refracting Telescope Kit, William Optics ZenithStar 61II Doublet Refracting Telescope – Gold, Celestron Travel Scope 70 Portable Telescope with Backpack, Celestron AstroMaster 70AZ Telescope, Celestron PowerSeeker 50 AZ Telescope, Celestron Travel Scope 50 Portable Telescope, Celestron Travel Scope 60 DX with Backpack, Celestron AstroMaster LT 70AZ Telescope, Celestron PowerSeeker 70 AZ Telescope, Sky-Watcher Evolux 62ED Doublet APO Refractor, William Optics ZenithStar 61II Doublet Refracting Telescope – Grey, Orion Carbon Fiber ED66 f/6.1 Doublet Refracting Telescope, Orion Observer II 60mm f/11.7 Doublet Refracting Telescope Kids Kit, Orion Observer II 70mm f/10 Doublet Refracting Telescope, Orion GoScope III 70mm Refractor Travel Telescope, Orion Observer II 60mm f/11.7 Doublet Refracting Telescope

Technical Specifications

Aperture: 2-2.75 inch (50-70 mm)

Focal Length: 360-900 mm 

Focal ratio: f/5.7-f/12.9

Highest Magnification: 122-165x

Light Gathering Power: 76-100x

Price: 85-730$

Images taken with 2-inch telescopes

Examples of 2-inch telescopes

2-inch

• Celestron PowerSeeker 50 AZ Telescope
• Celestron Travel Scope 50 Portable Telescope
• William Optics RedCat 51II – Upgraded Version

2.25-inch 

• Celestron Travel Scope 60 DX with Backpack
• Orion Observer II 60mm f/11.7 Doublet Refracting Telescope Kids Kit
• Orion Observer II 60mm f/11.7 Doublet Refracting Telescope

2.5-inch

• Orion ED66 CF f/6.1 Doublet Refracting Telescope
• Orion StarBlast 62mm Compact Travel f/8.4 Quadruplet Refracting OTA Telescope
• William Optics ZenithStar 61II Doublet Refracting Telescope – Gold
• Sharpstar 61EDPH II f/5.5 Triplet APO Refractor Telescope
• William Optics ZenithStar 61II Doublet Refracting Telescope – Red
• Radian 61 f/4.5 Imaging APO Telescope
• Sky-Watcher Evolux 62ED Doublet APO Refractor
• William Optics ZenithStar 61II Doublet Refracting Telescope – Grey
• Orion Carbon Fiber ED66 f/6.1 Doublet Refracting Telescope

2.75 inch

• Celestron Travel Scope 70 DX f/5.7 Portable Refractor Telescope with Backpack
• Orion Observer II 70mm f/10 Doublet Refracting Telescope Kit
• Celestron Travel Scope 70 Portable Telescope with Backpack
• Celestron AstroMaster 70AZ Telescope
• Orion Observer II 70mm f/10 Doublet Refracting Telescope
• Orion GoScope III 70mm Refractor Travel Telescope
• Universal Astro 70mm Refractor Travel Telescope
• William Optics Gran Turismo 71 APO Refractor with Flattener
• Celestron AstroMaster LT 70AZ Telescope
• William Optics RedCat 71 APO Telescope – Red
• Celestron PowerSeeker 70 AZ Telescope
• William Optics Gran Turismo 71 APO Refractor – Red
• Orion 70mm White-Light f/7.1 Solar OTA Telescope

How do 2-inch telescopes compare to other size-telescopes

2-inch vs 3-inch telescopes

2-inch telescope has less aperture than the 3-inch scopes. They offer a focal ratio of f/5.7-f/12.9 whereas the 3-inch telescopes vary from  f/3.9-f/12. Besides, 3-inch telescopes offer a focal length of 300-900 mm whereas the 2-inch telescopes start from 360 mm to 900 mm in focal lengths. Moreover, 2-inch telescopes provide 122-165x the highest magnification, whereas 3-inch telescopes can magnify up to 152-189x.

2-inch vs 4-inch telescopes

2-inch telescopes provide focal lengths of 360-900 mm (f/5.7-f/12.9), while 4-inch telescopes vary in focal lengths from 450-1350 mm (f/3.9-f/9). 2-inch telescopes provide the highest magnification of 122-165x, whereas 4-inch telescopes can magnify 204-236x. 

2-inch vs 5-inch telescope

5-inch telescopes provide a focal length of 650-1900 mm with a focal ratio of f/5-f/15. In contrast, 2-inch telescopes vary from 360-900 mm in focal length with a focal ratio of f/5.7-f/12.9. Moreover, 5-inch telescopes provide 225-260x the highest magnification, which is 122-165x in the case of 2-inch scopes.

2-inch vs 6-inch telescope

2-inch telescopes have less aperture than the 6-inch scopes. They offer a focal ratio of f/3.9-f/10 whereas the 2-inch telescopes vary from f/5.7-f/12.9. However, 6-inch telescopes offer a focal length of 162-1800 mm. On the other hand, 2 inch telescopes vary from 300-900 mm in focal lengths. 6-inch telescopes provide the highest magnification of 295-320x, whereas 2-inch telescopes can magnify 122-165x.