All about the Sky-Watcher EvoStar 72ED bezel

Sky-Watcher has recently completed its range of apochromatic refractors with the EvoStar 72ED. It is the smallest diameter in ED refractor of the brand which is aimed at amateurs looking for an instrument that is as transportable and light as possible. The EvoStar 72ED only weighs 2kg (with collars and dovetail) for a length of 420mm, its dew shield is even removable if necessary (but not retractable). The high optical quality of this model offers everyone the possibility of acquiring a high-performance instrument at a very attractive price for wide-field astrophotography, planetary/solar observation or autoguiding. The EvoStar 72ED will delight more than one amateur or beginner thanks to its good chromatism correction.

Chromatism correction by ED glass

To obtain the valuable qualifier "APO", a refractor must correct primary and secondary chromatic aberrations, inherent in all systems whose light rays pass through an optical element. In the case of the Sky-Watcher EvoStar 72ED, a doublet made up of an ED glass element reduces chromatism to considerably limit the appearance of colored edges on the planets or the Moon. The chosen ED glass, FPL-53 (Schott), is the best able to correct these defects thanks to a very low dispersion (NB: this doublet is different from the Black Diamond models).

he use of multi-layer coatings on all surfaces considerably limits losses due to the crossing of the lens, which makes the EvoStar 72ED brighter and more contrasty than conventional less well-corrected glasses. The "Metallic High-Transmission" (MHC) treatment is deposited on the air-glass surfaces ensuring breathtaking results (transmission close to 99.5%). Thanks to its very short focal ratio, f/5.8, the Sky-Watcher EvoStar 72ED refractor is particularly interesting for deep sky photography. In combination, for example, with a large format digital camera (corrector/reducer recommended), point the telescope towards large nebulae such as Orion, the Lagoon or the famous Andromeda galaxy.

Dual Speed ​​10:1 focuser

Focusing is obtained via a Crayford 2" focuser (in aluminium) offering robustness and precision during focusing. A clamping screw allows the focus to be maintained according to the orientation of the tube To be consistent with the optics and provide good results in astrophotography (where focusing is paramount) the EvoStar 72ED focuser has a fine 10:1 reduction screw.

To meet the requirements of amateur astronomers, the optical tube is entirely made of aluminium. No plastic parts are used! The solidity is therefore there as the aesthetics are particularly successful. The interior is blackened and baffled to limit the intrusion of parasitic lights. A Kodak pitch screw is positioned above one of the collars to parallel fit a camera.