Sky-Watcher 150mm f/7.8 Dobsonian Telescope
In recent years, Dobson fever has increasingly invaded amateur astronomers aware that the strongest sensations are felt with large diameter telescopes. The observation of the planets is indeed limited to Jupiter, Mars, Saturn (and the Moon) whereas the clusters, nebulae and galaxies are counted by tens in a 150mm instrument (see hundreds and thousands for the largest diameters under a sky dark).
Without motors or electronics, Dobsonians are indeed the instruments providing the most light, at a given budget, compared to any other type of instrument (mostly motorized and Go-To). Sky-Watcher designs solid tube Dobsonians appreciated by beginners and amateurs for many years through a range that extends from 150mm to 305mm.
The 150mm is the very first model in the range, allowing everyone to learn about observation. In a very dark sky you will be able to discover your first nebulae or globular clusters (the brightest objects of the famous Messier catalogue). You will be able to locate them and for the Orion Nebula for example to see many details. In summer with the majestic Milky Way (our galaxy) you can contemplate a maximum of objects.
For the beginner in visual observation it is the best price/performance ratio! Treat yourself to a "real" telescope without delay. Surprises and discoveries will be there for a minimal investment!
Optical design
The Newton design offers several advantages over other families of instruments (receivers and Cassegrain telescopes).
First of all, the manufacture of mirrors is more economical for an equal diameter and its focal ratio is generally very low. You then benefit for a very attractive budget from a bright telescope which provides a virtually coma-free field on the 150 and 200mm models (the 254 and 305mm with their short focal ratio, can be supplemented with a coma corrector) . The central obstruction is weaker than the Cassegrain type telescopes, if the collimation (adjustment of the mirrors) is well respected, the image quality is good in planetary. The Dobsonian mount also considerably reduces the price of this telescope compared to motorized equatorial mounts.
Unlike very cheap manufactures or small diameter Newtonian telescopes, the 150, 203, 254 and 305mm Newton (Dobson) Sky-Watchers have a parabolic primary mirror. The mirrors are spherically polished then recut to achieve a paraboloidal shape (more expensive and difficult to obtain). This is an essential selection criterion for instruments above 130mm and with a short f/D.
Mechanical concept
Sky-Watcher does not only offer telescopes at very advantageous prices but also easy-to-use instruments as shown by the tilting system which is fitted to all Dobsonians from 150 to 305mm. The Sino-Canadian firm has in fact developed and patented (United States Patent No. 6,940,642) a handle that allows you to tighten or loosen the fork on the optical tube. Thus, depending on the inclination of the tube and the weight of the accessories present in the eyepiece holder (binocular head, eyepieces of different angles), the observer can increase or decrease the friction. The tube is then sufficiently supported not to tip downwards as is the case with other constructions and free enough to be easily oriented towards another place in the sky.
Focusing is achieved through a bi-flowing focuser. A 31.75mm adapter is supplied as standard to use eyepieces of the same format from the 50.8mm output. A clamping screw located at the top of the focuser maintains focus according to the orientation of the optical tube. A 6x30 achromatic finder on its support is also delivered as standard. With a large diameter of 30mm for a magnification of 6x, it reveals objects invisible to researchers of smaller dimensions.
In terms of the material used for the primary mirror, the 254mm and 305mm Dobsonians benefit from a Pyrex glass which has the effect of reducing the effects of dilation due to thermal changes. Indeed, its coefficient of thermal expansion is lower than standard glass, which reduces its warm-up time and ensures better image quality.
Items Delivered:
- 1 Newton Sky-Watcher 153/1200 optical tube
- 1 Dobsonian azimuth mount
- 2 flowing eyepieces 31.75mm: Super 10mm and Super 25mm
- 1 finder 6x30
- User manual in French
