Ghosts in the Machine: the Astro-Tech AT111EDT...
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My acquaintance with zoom eyepieces dates back in 2001 with the purchase of my Leica 22-7.3mm Zoom for my Leica Apo-Televid 77. In 2003 I got my first astronomical telescope, a 115/805mm TMB/APM apochromat. The Leica Zoom was
I have managed to get in several nights testing my new Televue 8-24mm zoom; enough at least for a fairly good stab at a review. The weather has been warm and dry with mostly clear skies, though there has been a little broken cloud and occasionally some hints of mist forming later at night. The telescope used was a Helios 150 F8 refractor which is largely unmodified except for the tripod which has been replaced with a wooden one. The MV1 filter supplied by Sirius Optics, but now available in the U.K. was in place for the whole evening, attached
If you've lived long enough, you'll remember things like this Celestron (Vixen) zoom from the early 1980s. There were two types; One was like a Kellner with a barlow at the bottom and the other (above) was "orthoscopic." To put it mildly, they were not the greatest optical marvels on the amateur astronomy scene. Their zoom range generally ran from about 7-23mm which isn't bad. However, the optics and mechanics were no prize. They tended to be very restricted in field size, especially at the lowest power setting, on the order of 32 degrees apparent. Also, the field stop was only properly defined at one zoom setting. Some lenses weren't coated and the eyepiece had a tendency to expose sticky lubricating grease when the zoom was at its wide setting.
Good short focal length eyepieces with moderate to large apparent fields of view can sometimes be somewhat of a rarity, but such larger fields are a real necessity for those who are using the larger undriven telescopes. When a friend of mine suggested that I look at the Antares 5-8mm Speers-Waler eyepiece, I was somewhat skeptical about its wide field claims and variable focal length. However, once I got a chance to examine this nice piece of glass in detail, I too became a believer in this high power wide-field wonder. The 5-8mm Speers-Waler is a 9-element
How many times have you dragged out the umpteen gazillion pound Super Colossal Star Splitter with your 100 + assortment of EP’s only to find that the good ol’ trusty quick-look scope would have made the night viewing more productive? There has been considerable discussion/reviews devoted to various kinds of astronomy equipment for the amateur astronomer. This article will highlight the utility of one accessory – the zoom lens – as a useful quick-look tool.
I purchased an Orion Explorer II Zoom Eyepiece, in 1.25" format, from the Orion Cupertino, CA, retail store which is the closest store to my home that allows you to try and test out their optics. The main Orion retail/warehouse store in Watsonville, CA, also allows you to try out their optics, or to buy via mail order. I was intrigued by the relatively