One of the mysteries of the English language finally explained.
The apparent diameter of a planet or other celestial object measured by the angle which it subtends at the point of observation.
- ‘He estimated that its angular diameter was as small as one minute twelve arc seconds as opposed to the four or six arc minutes suggested by Kepler and by Tycho Brahe and by others.’
- ‘Its optical angular diameter is about 13 arcminutes, but viewed at radio wavelength at the frequency of neutral hydrogen, it extends considerably more than the angular diameter of the Moon.’
- ‘When the Earth is at its mean distance from the Sun, the solar orb has an apparent angular diameter of 0.533 degrees.’
- ‘Both, therefore, appear to have an angular diameter of about 1/2 degree as seen from Earth.’
- ‘It happens that the angular diameters of the Sun and the Moon as viewed from the Earth are about the same.’
- ‘Analysis of the contrast between the fringes revealed the angular diameter of the star to be 1.9 0.05 milliarcseconds.’
- ‘The asteroid's maximum angular diameter is only 2 to 4 arcseconds, which means it will be a starlike point of light in all but the very largest telescopes.’
- ‘Its angular diameter would be only 1.4 arc-seconds, though - less than that of Neptune as seen from Earth - so it would require serious magnification to clearly show a disk.’
- ‘Nevertheless it seems a staggering coincidence that the angular diameters of the Sun and the Moon are so similar.’
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