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| Shrinking of Apparent Star Diameters |
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| Reduction of star diameters since 1923 |
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The ZEISS Model I of 1923, the prototype of all projection planetariums, had an angular resolution of about 25 minutes of arc for the brightest (0th magnitude) stars. These are seen clearly as a disk. The most natural impression is achieved if the apparent star diameters are in the order of the human eye's resolving power of one to two minutes of arc. The best classical projectors had diameters slightly below 10 minutes of arc. With the fiber principle, star projections can have diameters subtending one minute of arc, so that all stars appear as needle-sharp, beaming points. | |
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