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Message: <blockquote data-quote="jcbouget" data-source="post: 1350226" data-attributes="member: 17837">A long time ago I looked through a Zeiss 8x56 BGAT without P coatings. I remember that for astronomy, the Zeiss was somewhat odd, because each star was at the centre of a faint cross. I have scanned an old Zeiss brochure that shows this phenomenon in a very realistic way. You should look at your screen one meter away, and imagine this is a chain of close double stars. This effect was invisible in the daylight, but I suppose that it reduces slightly the contrast of the image.I have now a very cheap 10x25 binocular without phase coating. The image is rather soft, but the star test shows other optical aberrations that may bury the phase shift effect. In the star test the Airy disc is clearly elongated in the focused image, like in this page : <a href="http://www.zbirding.info/Truth/prisms/prisms.htm" target="_blank">http://www.zbirding.info/Truth/prisms/prisms.htm</a>In my two other roof prism binoculars, the Zeiss 10x40 BGAT*P and Zeiss 10x42 FL, there is no trace of the little cross even on the brightest stars, and the Airy disc appears to be as round as possible considering the presence of other aberrations. So I think that well made phase coatings are very effective.Jean-Charles</blockquote>