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Mk II RA bino: "What the 'L'!"

Mk II RA bino: "What the

Assembled, with the 60mm objectives and 13mm Ethos eyepieces installed. No sleek lines or sexy curves here. But the monstrously wide views never fail to engender exclamations from others. This configuration yields 21X60 with a 4.7 degree field.

    • LU1AR likes this

    Mar 05 2010 08:51 PM
    Sweet! How is the image quality in this configuration? Is it "tack sharp to the edge" type of view, or can you tell that the Ethoi are pulling weight optically-speaking?
    Apr 14 2010 06:46 PM
    Not sharp to the edge, mainly because of field curvature, which to first order scales inversely with focal length of the objective. But compared to other lesser eyepieces (especially from binoculars), the Ethos is indeed "pulling its weight" due to its high degre of correction. The edge sharpness is about on par with that exhibited by an eyepiece having only half the AFoV. And what's more important to me, the area of the view is 4X larger!
      • LU1AR likes this
    What the "L" is right!!! Wow!!!
    Brian Albin
    Apr 14 2011 11:28 AM
    Hello Glenn, I have the Tento 20x60 and have never been happy with the view. I have wanted to replace the 20 power EPs with 12 power to widen the view and make it sharp across the field, instead of soft in zones as now, but did not know what focal length to buy. So I am glad to read that the original is something like 13.5mm. It looks like 23mm would put me at 12M. But I wonder if my true view will widen any if I do not also put in wider prisms to avoid vignetting.

    ¡Nice "Motivational Piece"!. Thanks.

    Now that I think about it, I wonder why the 90° binoscopes (like the APM ED-APO series) don't just leave the image inverted - I assume that permits the use of simpler prisms and yield better image quality at the same time. I can't use the 90° type for terrestrial applications anyway.

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