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SYNOPTICAL TABLES.
| Magnitude of the smallest stars visible, | 7th |
| Magnitude of the stars visible by the most powerful telescopes, | 16th |
| Light of a star of the 6th magnitude (1st magnitude = 1), | 1-1OOth |
| Number of stars of 1st magnitude, | 24 |
| Number of stars of 1st magnitude, 2d magnitude, | 50-60 |
| Number of stars of 1st magnitude, 3d magnitude, | 200 |
| Number of stars total registered to 7th magnitude, about | 15,000 |
| Number of stars total visible in Herschel's 20-feet telescope, | 5,500,000 |
| Rate at which light travels per second, in miles, | 200,000 |
| Time required by light to traverse the distance of a star with one second of parallax, in years, | 3y. 83d. |
| Corresponding distance in billions of miles, | 20 |
| Distance of smallest stars seen in telescopes of 75 space penetrating power, measured by light in years, | 2,000 |
| Star 61 Cygni, parallax first detected in it, by Bessel, | 0″.349 |
| Star 61 Cygni, proper motion annually, | 5″ |
| Star 61 Cygni, distance of component stars, | 15″ |
| Star 61 Cygni, sum of masses of the component stars (Sun = 1), | 0.353 |
| α Centauri, parallax, | 0″.9128 |
| α Centauri, nearest star, distance measured by light, in years, about | 3.5 |
| α Centauri, proper motion, | 4″ |
| Number of stars to which parallax has been assigned, | 9 |
| Probable average distance of stars of 1st magnitude, measured by light, in years, | 15.5 |
| Probable average distance of stars of 2d magnitude, | 28 |
| Probable average distance of stars of 3d magnitude, | 43 |
| Probable average distance of stars of 4th magnitude, | 60 |
| Probable average distance of stars of 5th magnitude, | 84 |
