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Message: <blockquote data-quote="henry link" data-source="post: 3437589" data-attributes="member: 6806">I have a request for those who will get a look at the new Zeiss scope at Birdfair. Could someone among you try to do a quick 60X star-test? Ideally someone who is familiar with star-testing can do this, but anyone can learn how do do it by Googling something like "telescope star-test" and practicing a little. Hopefully there will an example of a glitter point of the sun returning from some small round shiny object between maybe 20m and 50m (too close and it may not be small enough to act as a point source, too far and there may be too much air turbulence to see clear diffraction rings). A car in sunlight has many such glitter points in the head/tail lights and trim areas or you could bring your own little shiny object. Rack the focus back and forth and observe the diffraction rings on either side of focus and the point of light at best focus. These reveal the level of spherical aberration and various defects like astigmatism, coma, turned edge, zones, pinching and poorly made roof prisms. One accurate description of a star test is far more informative of the true optical quality of a particular scope specimen than all the subjective descriptions we are likely to read of what birds look like through it.Henry</blockquote>