The heart of William Optics’ Super ZenithStar 103 f/6.9 imaging APO is a f/6.9 air-spaced FPL53 doublet housed in a CNC-machined ultra-precision lens cell. Add a 0.8x flattener/reducer, and the focal ratio becomes f/5.5. Focus duties are performed by the Zenithstar 103 ultra-robust 2.5-inch, 1:10 dual-speed, rack-and-pinion focuser with […]
Sky-Watcher USA Evoguide 50: Sky-Watcher USA is noted for its quality apos, and the new Evoguide 50 ($275US), its smallest, is also among its most intriguing, not the least because it features a matched lens assembly, which includes an ED element, earning it the ED Doublet “apo” designation. With a […]
CFF Telescopes Apo Refractor Telescopes Whether you are a resolute visual observer or dedicated astro-imager, refractor telescopes offer unique advantages. But, the physics of light being what they are, no single refractor is best at both pursuits, and given the understandable recent market focus on refractors for astrophotography, those of […]