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Old 29-04-2012, 10:18 AM
Wavytone
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Join Date: Jul 2008
Location: Killara, Sydney
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Quote:
Originally Posted by mental4astro View Post
"Fishbowl" effect then. The image displayed a distinct deformation as the scope was moved across the field, like that seen in a big, fat magnifying glass.
Alex, that's pincushion distortion. It is common in eyepieces incorporating the Smythe lens design; essentially it means magnification is not constant across the field and varies radially from the centre.

Hehe I'm not surprised at your other remarks especially transmission, I have noticed that before. You tried the LVW's before at Katoomba and decided they were not exceptional so it' not really news...

As Robert said, there is a huge tradeoff in how much glass and how many surfaces vs field of view, transmission, contrast and image quality. For this reason if you're really serious about smallest objects rather than wide fields the best choice is an eyepiece with only 2-4 elements and few glass/air surfaces. This is why designs such as super-monocentrics, RKE, Plossl, orthoscopic and even Kellner are still useful. I often wonder what could be done if some of these older designs were revamped to take advantage of modern glass types, in particular ED glass.

Choosing eyepieces is an area where there are too many conflicting variables, about which most of us have little or no real information to make a decision. That leaves 'trying before buying' or pot luck. You're fortunate to be able to try alternatives, which was something I couldn't do at the time I bought them (they were half the price of Naglers too).

Last edited by Wavytone; 29-04-2012 at 10:33 AM.
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