The 90/900 Sky-Watcher refracting telescope is recommended for anyone looking for a good quality telescope for lunar and planetary observations.
The objective lens is a 90 mm Fraunhofer air spaced achromatic lens with 900mm focal length with a theoretical resolution of 1.3". The Cassini-division in Saturn's ring system or the Great Red Spot on Jupiter can be seen, including martian polar caps and continents. All of the Messier object are reachable (dark skies required) and many globular clusters and galaxies can also be observed. The telescope comes with 2 Barium eyepieces (10 and 25mm) providing 36x and 90x magnification, an achromatic Barlow lens. The Barlow lens feature a T2 thread and thus can be used for photography. The focuser also has a T2 mount. A 6x30 spring load achromatic finderscope is included which can be removed in a second for transportation. The mount is an EQ-2 model which is more robust than the EQ-1 and can be equipped with a clock drive. A star diagonal (adjustable to 45 or 90 degrees) is also included.
This optics is equipped with an achromatic objective. Because of a special combination of two lenses within the objective, most of the colour aberrations can be corrected. Thus, you do not have to face so many disturbing irregularities as usual with common Fraunhofer refractors. The aperture ratio of 1:10 has an additional positive effect.
This parallytic mounting bares already the opportunity to arrange optics exactely to the polestar. For each watching-place, the right pole-height/geographic amplitude can be set. The objects can be set and tracked with fine movements in the right ascension- and declination-axe.
The aluminium three leg-tripod is extendable in a height from 71 cm up to 121 cm.
|Type of build||Achromat|
|Focal length (mm)||900|
|Aperture ratio (f/)||10|
|Limit value (mag)||11,6|
|Light gathering capacity||170|
|Max. useful magnification||180|
|Tube construction||Full tube|
|Type of build||Gear rack|
|Connection ( to eyepiece)||1,25"|
|Type of build||EQ-2|
|1.25'' eyepieces||25mm, 10mm|
|Deviating optics||1.25", 90° star diagonal|
|Total weight (kg)||11,7|