Achromatic Refractor Telescopes for Astronomy & Terrestrial Viewing
Achromatic refractor telescopes are classic lens-based telescopes offering straightforward operation, high-contrast views and low maintenance. Depending on aperture and focal length, they are suitable for observing the Moon, planets, star clusters, wide star fields and many other celestial objects, while selected models can also be used for terrestrial viewing.
Discover achromatic refractors as complete telescope packages with mount and tripod, computerised GoTo systems or optical tube assemblies (OTA) – from compact beginner telescopes to large-aperture wide-field refractors.
Achromatic Refractor Telescopes – Classic Telescopes for Visual Astronomy
The achromatic refractor is one of the classic telescope designs used in amateur astronomy.
A refracting telescope collects and focuses incoming light through an objective lens. An achromatic objective typically combines two different types of optical glass to significantly reduce the colour error that would occur with a simple single lens.
Achromatic refractors are popular because of their straightforward operation, high-contrast views and relatively low maintenance requirements.
Who Is an Achromatic Refractor Suitable For?
Achromatic refractor telescopes are particularly suitable for:
- astronomy beginners
- lunar observation
- planetary observation
- double stars
- open star clusters
- bright deep-sky objects
- wide star fields
- terrestrial observation
- portable astronomy
The ideal observing targets depend primarily on the aperture, focal length and focal ratio of the telescope.
Long-Focal-Length Refractors for the Moon and Planets
Achromatic refractors with longer focal ratios such as f/10 or f/12 generally show less noticeable chromatic aberration than short, fast achromats.
They are therefore particularly suitable for medium and high magnifications.
Typical targets include:
- lunar craters and mountains
- Jupiter and its moons
- Saturn and its rings
- Mars during favourable apparitions
- double stars
- bright star clusters
A classic long-focus refractor can therefore be an excellent telescope for visual lunar and planetary astronomy.
Short-Focal-Length Achromats for Wide-Field Observation
Short achromatic refractors have a different strength.
Fast instruments with focal ratios around f/5 or f/6 provide wide fields of view and are particularly useful at low and medium magnifications.
Suitable targets include:
- large open star clusters
- extended nebulae
- rich star fields
- regions of the Milky Way
- comets
- terrestrial targets
Their compact optical tubes also make short-focus refractors attractive as portable and travel telescopes.
At high magnifications on bright targets, however, chromatic aberration becomes more noticeable.
What Is Chromatic Aberration?
Different wavelengths of light are refracted by slightly different amounts when passing through a lens.
An achromatic objective greatly reduces this effect compared with a simple lens but does not eliminate it completely.
A violet or blue fringe may therefore become visible around particularly bright targets such as the Moon, Jupiter or bright stars.
The amount of visible chromatic aberration depends on factors including:
- aperture
- focal length
- focal ratio
- magnification
- observing target
In general, slower achromatic refractors show less noticeable false colour than fast achromats of a similar aperture.
Achromat or ED/APO Refractor?
Achromatic refractors provide a relatively affordable introduction to lens-based telescopes.
ED and apochromatic refractors use specialised optical glass and more sophisticated objective designs to provide improved colour correction.
Achromatic refractors are particularly attractive for:
- budget-conscious beginners
- visual astronomy
- lunar and planetary viewing with long focal ratios
- wide-field observation with short focal lengths
- terrestrial observation
ED and apochromatic refractors are particularly useful when improved colour correction is required or when the telescope is intended for demanding astrophotography.
For visual astronomy, however, a good achromatic refractor can offer excellent value.
Choosing the Right Aperture
A telescope's aperture determines how much light it can collect and influences its resolving power.
Smaller refractors with approximately 60 to 80 mm aperture are compact, lightweight and easy to operate. They are well suited to beginners, lunar observation and bright celestial objects.
Refractors with approximately 90 to 102 mm aperture collect more light and provide additional resolution.
Models with apertures of 120 mm or more provide greater light-gathering capability but also require a correspondingly stable mount.
Choosing a Mount for a Refractor Telescope
The mount is just as important as the optical tube for comfortable observing.
Long refractor tubes create considerable leverage, so the mount should provide sufficient stability.
Alt-Azimuth Mounts
An alt-azimuth mount moves the telescope vertically and horizontally.
It is intuitive to operate and particularly suitable for beginners, quick observing sessions and terrestrial viewing.
Equatorial Mounts
An equatorial mount can be aligned with the Earth's rotational axis.
Once properly aligned, celestial objects can be followed by moving primarily one axis, making this type of mount particularly convenient for astronomical observation.
GoTo Mounts
A computerised GoTo mount can automatically locate numerous celestial objects after the system has been aligned.
This is useful for observers who want to locate targets quickly or would like electronic assistance navigating the night sky.
Complete Telescope or OTA?
This category includes different configurations.
Complete telescope packages may include:
- optical tube
- mount
- tripod
- finder
- star diagonal or prism
- eyepieces
- Barlow lens
- additional accessories
They are particularly convenient for beginners looking for a ready-to-use system.
OTA stands for Optical Tube Assembly and generally refers to the optical tube without a complete mount and tripod.
An OTA is ideal if you already own a suitable mount or want to build an individual telescope setup.
Achromatic Refractors for Terrestrial Observation
Many achromatic refractors can also be used for terrestrial viewing.
With an appropriate erecting or Amici prism, they can provide an upright, correctly oriented image suitable for observing landscapes, wildlife and distant terrestrial objects.
Compact short-focus refractors are particularly convenient for this type of use.
Achromatic Refractors for Astrophotography
Achromatic refractors can also be used for imaging.
Many models are suitable for lunar photography, basic planetary imaging or first experiments with a camera.
For demanding deep-sky astrophotography, however, the remaining chromatic aberration becomes more noticeable. ED or apochromatic refractors are therefore usually preferred for colour-critical deep-sky imaging.
Short achromatic refractors may also be useful as guide scopes or for specialised wide-field applications.
Accessories for Achromatic Refractors
A refractor telescope can be adapted to different observing applications with suitable accessories.
Useful additions include:
- additional eyepieces
- Barlow lenses
- star diagonals
- Amici prisms
- lunar filters
- nebula filters
- finder scopes
- smartphone adapters
- camera adapters
- mount motors
- transport bags
Always check connection size, thread type and compatibility with the telescope and mount before purchasing accessories.
Achromatic Refractor Telescopes at Optikshop24
Optikshop24 offers achromatic refractor telescopes for a variety of observing requirements – from compact beginner telescopes to larger refractors for ambitious visual astronomy.
Choose between complete telescope packages with mount and tripod, models with computerised GoTo control and optical tube assemblies for use with an existing mount.