If you're looking for a moderate-aperture apochromat
, consider the new arrival from TMB's Signature Series, the TMB-130.
Those more experienced, however, will recognize that the Petzval, SD, and apochromat
terms worked into the respective Zenith Star monikers (not to mention the prices) suggest different levels of optical performance.
The Fluoro-Star FLT-110 is William Optics' first true apochromat
, employing a triplet lens designed and fabricated by Telescope Engineering Company (TEC) in Golden, Colorado, itself the producer of a growing line of fine telescopes (its 140-mm apo was reviewed in our December 2003 issue, page 54).
This dramatic reduction in focal length means that even a 7-inch apochromat
can be transported to a star party or remote dark-sky observing site.
(By the way, achromat means "without color," while apochromat
means "without color--but, we're serious this time." If someone invents a refractor with color correction superior to that of an apochromat
, we're going to have to come up with a new name.)
Sigler, "Glass selection for airspaced apochromats
using the Buchdahl dispersion equation," Applied Optics, vol.
provide the best possible performance per unit of aperture, and are also ideal for astrophotography.
are free of the halo issue, but big ones are extremely expensive.