Doublet Apos

  • Neil English
Part of the Patrick Moore's Practical Astronomy Series book series (PATRICKMOORE)


Times, they are a changing! Just a decade ago, apochromats of any genre were prohibitively expensive to all but the wealthiest of us. That changed forever in 2004, when Orion USA launched its revolutionary new low cost Apo, the ED80, which, for the first time, brought a taste of the color free to many amateur astronomers. The telescope boasts a doublet objective with one element made from FPL-53 ED glass. Its 600 mm (F/7.5) focal length makes it a versatile telescope for visual and photographic applications. If you’ve only ever used achromats, you’ll immediately know that you’re looking through an Apo when you first look through this telescope. The original ED80 (made by Synta for Orion USA, Celestron, and Sky-Watcher) is chunky for a 3.2 in. telescope. Measuring in at 24 in. long and tipping the scales at over 6 pounds when used with a diagonal, this doublet Apo packs a satisfying optical punch. Star fields are variegated in vivid detail. Contrast at low to moderate powers is noticeably better than achromats of the same specification. And it takes magnification really well – 200× on a good night. I took my blue-tube Sky-Watcher ED80 with me on vacation to a dark sky site in southern Portugal a few years back and set it to work over several sultry August evenings. Despite some overlying haze, Jupiter was brighter than I had ever seen it before. Conditions were perfect for testing the mettle of this telescope, but I wanted to enjoy myself, too! The ED80 delivered razor-sharp views of the giant planet at 120× with four of five bands clearly discernible at a glance. The planet’s image at 200× was still very well defined, but some false color was beginning to creep in, washing out the most subtle atmospheric features. That said, I could clearly make out the tiny disks of Europa and Ganymede against an ink-black sky – a magical moment for me! Color correction is very impressive in this telescope. Gems such as Albireo in Cygnus and Almaak in Andromeda presented in their most beautiful, contrasted pastels.


Focal Length Giant Planet Spherical Aberration False Color Color Correction 
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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.GlasgowUK

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