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nobody

09 Apr 2019 21:54



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Povestea cu 50*D(inch) este legata mai mult de stelele duble "de laborator" (Dawes' limit).

The often quoted 50x per inch of aperture limit to useful magnification dates back to the 1940s, when Allyn Thompson used a mixture of theoretical diffraction resolution limit for point-like sources, anecdotal accounts of the limit to naked-eye stellar resolution (ε Lyrae), and the results of group's own experiments with naked-eye resolution limits for pairs of 0.0003-inch illuminated pinholes, to come up with four arc minutes as the approximate average resolving limit for point-like objects (Making your own telescope, p173-174). Combining it with the Dawes' limit formula for the minimum resolvable stellar separation in arc seconds α=4.56/D for the aperture D in inches, for the corresponding magnification M needed to enlarge this limit to four arc seconds (i.e. 240 arc seconds), produced M=240/α=52.6D.
Increase in magnification up to 70x per inch, with each FWHM enlarged to about 5 arc minutes still results in small gains, and is needed to achieve the ultimate resolution limit.

Iar la obiectele extinse, treaba devine mai complicata, acolo merge pe incercate.