The ES 305mm f/5 Ultra Light arrives in a single 49 × 56 × 103 centimetre box that tips your bathroom scales at 34 kilograms, so you can be forgiven for thinking from the outset that ‘Ultra Light’ is something of a misnomer. Note the foam stray-light shield opposite the focuser, which attaches with Velcro. By colour-coding the truss tubes for repeatability, you may not need to collimate the secondary each time you set up. The well-conceived and implemented secondary collimation system is shown here. However, the secondary cage truss mounting lugs shown here can be moved to an intermediate set of holes, affording a total of eight possible positions for your viewing comfort. The secondary mirror cage can be attached to the trusses in one of four orientations, positioning the focuser pointing up, to the left/right side, or towards the ground. It has a 1:10 reduction ratio on the fine-focus knob and a two to 1.25-inch eyepiece adaptor.Image: Ade Ashford. The focuser is a hybrid Crayford with a rack-and-pinion action over a 5cm range with an engraved millimetre scale. For the purpose of this review we obtained (anonymously) a 305mm Explore Scientific Ultra Light Dobsonian for an extensive evaluation during the autumn of 2020.
Clearly, these are very important qualities in the UK’s maritime climate. Unlike traditional Dobsonians, the ES Ultra Light range dispenses with plastic-coated, dense particle board construction in favour of powder-coated aluminium for strength, lightness and resistance to corrosion without the moisture-absorbing qualities of chipboard. Each is modular in design, breaking down into compact, easy-to-assemble units for ease of transportation in even a small car to set up at dark-sky sites. The smaller models are both f/5, while the larger are f/4.6 and f/3.6, respectively. JOC owns a number of familiar company names, including Bresser in Germany and Explore Scientific (ES) in the USA.Įxplore Scientific currently sells a range of truss-tube Ultra Light Dobsonians encompassing four models of 254mm, 305mm, 406mm and 508mm aperture. Better known in the West as simply JOC, it’s one of the largest optoelectronic manufacturers in China. John Dobson lived in the United States from the age of 12, but he was born in Beijing, some 2,000 kilometres north of the city of Guangzhou, currently headquarters of Jinghua Optics and Electronics Co., Ltd. It took nearly 300 years from Sir Isaac’s original proof of concept before John Lowry Dobson (1915–2014) created the minimalist fusion of Newtonian optics with a stable, easy-to-use mount, and hence the Dobsonian was born. Yet even the best telescope is useless without an effective mount and, depending on its sophistication, a mounting can cost many times the cost of the instrument itself. However, not every observer possesses the practical skills (or inclination) to grind and polish their own mirrors, so a little background reading quickly informs you that it’s hard to beat the performance-to-cost ratio of a Newtonian when seeking the largest quality telescope for your money. The elegant simplicity of Isaac Newton’s two-mirror reflecting telescope design from 1668 has inspired generations of amateur makers. The Explore Scientific 305mm Ultra Light truss-tube Dobsonian is actually quite heavy, weighing nearly 30 kilograms.
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