Telescopes

Our telescopes are entirely designed and manufactured in Europe, with optics made in the Netherlands. While we aim to bring high quality systems to the amateur sector with modular and standardised designs we remain a custom systems specialist and customisation is always an option with us.

Refractor
Classical Cassegrain
Newtonian
Prime-focus Newtonian

Refractors vs reflectors

The refractor is the most popular telescope design in the world due to its ability to maintain alignment better than almost any other telescope. They are adaptable for all sorts of activities besides astronomical viewing. In comparison to reflectors, refractors lack central obstruction in the light path. Loss to a secondary mirror is made up by the fact that large mirrors can be supported from the back side. Large lenses must rely on their rims for all their support. No successful refractor greater than 1 meter has ever be built. Large unsupported glass lenses bend under their own weight resulting in distorted images.

Among the reasons why large telescopes are reflectors is cost. Mirrors are cheaper to manufacture than lenses. Mirrors need only one surface formed rather than four surfaces (both sides of the convex and concave lens). Large glass discs for mirrors can be chosen for the resistance to thermal expansion and warping. The glass can be translucent or even opaque. In fact, some reflectors were made entirely of metal. Refractors must chose glass for its optical qualities. Unfortunately, the best optical qualities, the best strengths and the best temperature insensitivity are not found in a single type of glass.

Cassegrain reflector

The Cassegrain reflector design relies on a combination of a primary concave mirror and a secondary convex mirror. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system. In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the centre thus permitting the light to reach an eyepiece, a camera, or a light detector. Alternatively, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror(s) may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the primary mirror (or both).

The classic Cassegrain configuration uses a parabolic reflector as the primary while the secondary mirror is hyperbolic. Modern variants often have a hyperbolic primary for increased performance (for example, the Ritchey–Chrétien design), or the primary and/or secondary are spherical or elliptical for ease of manufacturing.

Ritchey–Chrétien

This telescope is a specialized Cassegrain reflector which has two hyperbolic mirrors (instead of a parabolic primary). It is free of coma and spherical aberration at a nearly flat focal plane if the primary and secondary curvature are properly figured, making it well suited for wide field and photographic observations. This is the most popular design in the world of professional reflector telescopes.

Dall–Kirkham

This design uses a concave elliptical primary mirror and a convex spherical secondary. While this system is easier to grind than a classic Cassegrain or Ritchey–Chrétien system, it does not correct for off-axis coma. Field curvature is actually less than a classical Cassegrain. Because this is less noticeable at longer focal ratios, Dall–Kirkhams are seldom faster than f/15. These telescopes often require a corrector for wide field applications.

Newtonian reflector

This telescope type uses a concave primary mirror and a flat diagonal secondary mirror. The Newtonian telescope's simple design makes it very popular with amateur telescope makers.

The biggest drawback to the Newtonian design is the placement of the eyepiece. In smaller scopes, this isn't much of a problem, but in larger scopes, the eyepiece may wander all over, requiring a step ladder and contortions. Two lesser drawbacks are vibration and balance. Newtonian have the eyepiece or instrument package at the front at the end of a long lever arm. Heavy counter weighting is required at the back to balance these tools. Changes in eyepieces or instruments requires re-balancing. Touching the scope or wind is very likely to set up major vibrations.

Prime-focus Newtonian

One way the Newtonian design is modified is by installing a camera at the prime focus. This has the advantage that fewer lenses, prisms, and mirrors are in the light path. Each optical element causes some light to be lost. Newtonian cameras make use of every available bit of light. They are very effective as long as the camera diameter does not cause an unacceptable central obstruction.

Dobsonian

A Dobsonian telescope is an altazimuth-mounted Newtonian telescope with a simplified mechanical design. It is optimized for observing faint, deep-sky objects such as nebulae and galaxies. This type of observation requires a large objective diameter (i.e. light-gathering power) of relatively short focal length and portability for travel to relatively less light-polluted locations. The term Dobsonian is currently used for a whole range of large-aperture Newtonian reflectors that use some of the basic Dobsonian design characteristics, regardless of the materials from which they are constructed.