THE ARRAY OF PLANETS

Evening Post, Volume CIII, Issue 141, 17 June 1922, Page 9

THE ARRAY OF PLANETS

(By James B. Strachan.)

The opposition of Mars which occurred at' half-past one last Sunday morning accounted for the very large attendance at the Kelburn Observatory last Tuesday evening.

This opposition, or its angular distance of 180 degrees from the sun as seen from the earth is apparently coincident or nearly so with its nearest approach to the earth on its present round.

The telescope in the Observatory is a S^-inch refraetms one, equatorially imounted, that is, if the instrument is in good adjustment, and the circles of right ascension and declination are set correctly to the Nautical Almanac position of any particular star, and the clock attached to the telescope set in motion and regulated to keep sidereal time, the telescope will follow the star from its rising to its setting, in other words, it will act equally and opposite to the rotation of the earth. ' It will not follow Mars or other planets, the sun. moon, or comets, and would, therefore, in their cases, require periodic adjustment. Eight aseention and declination are the co-ordinates ■used to fix the position of an object on the apparently moving celestial sphere i inst as latitude and longitude are used to fix the position of a point on the apparently stationary earth.

A (treat, number of the interesting •celestial objects ■were above the horizon on Tuesday nieht: soma early, and some later on. including Saturn, Jupiter, Mars, tlm waning gibbous moon, double and triple stars., and various star clusters. Venus also was above the horizon in the early evening-. This nlan°t. which is now seen in thp. west shortly after .sunset, Warns an "evening star" on 9th jj'ebruaiv last, and will set, later and 1 'er every night until ii)sJMk Septcm*

ber, when it will be at its widest angle from the sun. It will then begin to close in to the sun, increasing in brilliance to a maximum on 21st October. Continuing to close in to the sun, it will disappear in its Tays and will become a "morning star" on 25th November. The earth advancing in its path will cause the planets Saturn and Jupiter to disappear in the suu's rays, until on the sth and 23rd October respectively they will become "morning stars." For the same reason Mars, which was in opposition last Sunday morning, will close in to the suxi. until on the 9th August, 1923, it will likewise become a "morning star." When seen through the telescope, the ragged edge of the moon where the light of the sun ended showed up the mountains on its surface, whose height can he found approximately if the angle at which the light of the sun strikes .the. surface be known and the lengths of the shadows be measured. Saturn's rings appeared to be not a great way removed from the place of observation. The interesting phases of the_ four larger satellites of Jupiter in their disappearances, reappearances, crossings, and shadow crossings did not appear at their best. Some' of the markings on Mars were faintly seen.