SharpStar D 150mm f/2.8 HNT: An imaging telescope with sharp vision

27 May 2020 Ade Ashford

Until comparatively recently, if you wanted to capture extended deep-sky objects such as diffuse emission nebulae and supernova remnants with your full-frame DSLR or CCD/CMOS camera, then your best option was to invest in an f/2 or f/2.8 telephoto prime lens from one of the big-name players in photography. Such high-precision solutions possess multi-element lenses, often made of exotic glass, and sometimes with aspheric shapes designed to ensure tight control of false colour, off-axis aberrations and field curvature over a large imaging sensor. Not surprisingly, lenses possessing these desirable characteristics don’t come cheap. For example, a Nikon 200mm, f/2 G ED AF-S Nikkor VR II or Canon EF 200mm, f/2 L IS USM will each lighten your bank balance by more than £5,000. While f/2 and f/2.8 prime lenses can record bright nebulae and galaxies in minute-long exposures at the high ISO sensitivities of modern DSLRs, 200 and 300mm focal-length lenses are too short to reveal fine detail in small-scale examples of these deep-sky objects, unless one is prepared to use one of the new breed of cameras employing CMOS sensors with tiny (less than 2.5 micron) pixels. Even so, most astro-imagers would prefer focal lengths of at least 400 to 500mm

Picture This

A hundred thousand supernovae

4 May 2020 Astronomy Now

Countless stars fill the scene in this revealing infrared view of the central region of our Galaxy, the Milky Way, taken by the European Southern Observatory’s Very Large Telescope.