Takahashi Abbe MC Ortho
https://www.cloudynights.com/topic/474675-the-takahashi-abbe-ortho-a-brief-summary/正交鏡
https://www.astroshop.eu/eyepieces/15_10/a,Zubehoer.Allgemein.Bauart=orthoscopicFOA : Fluorite Ortho Apochromatic
FOA-60 from Takahashi is a new compact apochromatic fluorite doublet refractor.
http://s00639.blogspot.com/2017/04/foa-60.html ==
TOA : Triplet Ortho Apochromatic Ortho-Apochromat concept
Triplet Ortho-Apochromat concept of the TOA refractors makes it possible to combine sharpness and extraordinary contras
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Orthoscopic eyepieces have four lenses, of which two are biconvex curved and one biconcave. They offer a high degree of sharpness in the centre as well as at the edge. That's why they are interesting for observing planets and double stars. The advantage: they offer a flat field of view.
The low loss of light is another advantage of these eyepieces. The apparent field of view is approximately 40° – 45°.
OTHERS 正交偏光鏡
https://baike.baidu.hk/item/%E6%AD%A3%E4%BA%A4%E5%81%8F%E5%85%89%E9%8F%A1/6849545
