This telescope is a refractor style scope, which is probably what most people imagine when they think of a telescope. The design consists of a lens group at the front of the scope, and an extending focus drawtube to the rear.

This specific model is a doublet style refractor, meaning that it has 2 lens elements in the group. The reason for this is to reduce the effect of a phenomenon known as chromatic aberration. This comes from the fact that with lenses, the focal point is not the same for all wavelengths of light. The second lens element is designed to reduce the difference in focal lengths across the wavelength range of visible light, thereby reducing the chromatic aberration effect.

The number 72 in the name of this scope refers to its aperture, which is 72mm in diameter. It has a focal ratio of approximately f6, which indicates a focal length of around 430mm (6 x 72mm). The true focal length can only be determined by analysing images captured through the specific scope in question because very small deviations in the manufacturing tolerance of the lens can cause shifts in the focal length.

Further information about this scope can be found on the Skywatcher website.