![]() ![]() Such exquisitely crafted instruments from high-end manufacturers such as Takahashi and Astro-Physics use exotic glasses, ground and polished to complex geometries, to create compact refractors that provide essentially perfect imagery for visual and photographic use, but they usually command an eye-watering price. In the intervening years, opticians have developed so-called ‘apochromatic’ (or ‘apo’) refractors, typically composed of a three-glass element sandwich capable of bringing three colours of the visible spectrum (typically red, green and blue) to a common focus. The anti-reflection coatings are so good that it requires a bright source to render them visible to the camera. The 60mm, f/6 air-spaced doublet is fully multi-coated and composed of highly desirable low-dispersion FPL53 glass and a matching lanthanum element for excellent colour correction for both visual and photographic applications. However, for an achromat of typically encountered sizes to have an acceptable level of colour correction, an optician needs to make the instrument’s focal length at least twelve times the diameter (or aperture) of the lens, which immediately explains the long tubes of classical refractors. In fact, the use of crown and flint types of glass to fashion a so-called ‘achromatic’ lens capable of bringing two wavelengths of the colour spectrum (usually red and blue) to focus dates back to the British inventor Chester Moore Hall, in around 1730. ![]() I quickly learned that a simple compound lens composed of a sandwich of two types of glass with opposing dispersive (prismatic colour-making) qualities only goes a limited way to cancelling out this annoying inherent defect of refractors. Thus I had my introduction to the bane of simple lens-based instruments: chromatic aberration. While I was immensely proud of my four-inch, f/5 refractor, its images of the Moon and bright planets were surrounded by a vivid purple halo. I built my first telescope out of a 100mm diameter, two-element government surplus lens of 500mm focal length in the early 1970s. ![]() Each apochromat is tested and optimally collimated on the optical bench by Teleskop-Service before shipping, so you have an optimal telescope for your application from the beginning.For casual terrestrial observations and quick looks at the Moon the TS PhotoLine 60mm, f/6 is quite at home on a sturdy photo tripod such as the author’s Manfrotto 055 shown here.Weight only 9 kg with a length of 1.1 meters - so the apo is still very portable. ![]() CNC tube rings with Losmandy style dovetail bar.Sturdy aluminium tube with internal baffles.Working distance 130 mm from the 2" receptacle, so you can easily get into focus with common accessories - 230 mm without extension.Direct M63 threaded connection for correctors and reducers for astrophotography.2.5" dual-speed RAP Photoline rack and pinion focuser - holds accessories up to 5 kg.Temperature compensated, fully adjustable metal cell.Well corrected, air-spaced doublet objective - special glasses FPL53 (from Ohara) and Lanthanum glass.The advantages and features of the Photoline 150 mm f/8 Apo: Whether you are interested in solar and planetary photography and observation, or astrophotography of nebulae, star clusters and galaxies, this telescope will give you a very good performance. The inexpensive yet powerful optical concept makes this dream telescope affordable for amateur astronomers. It has the same optical design as the successful Photoline 125 mm f/7.8 apo. The TS 150EDF is the largest ED doublet refractor. ![]()
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