EXPLANATION. -The white spaces show the amount of moonlight each night. January 7, Feb ruary 6, etc., new moon, no moonlight during the whole night; January 15, February 14, etc., the moon sets at or near midnight, when the first half of the night has moonlight: January 22, February 21, etc., full moon when moonlight lasts the whole night; January 29, February 27, etc., when the moon rises at or near midnight when the latter half of the night has moonlight. aAndromedie(Alpher'z) + 28 36-1 18.0 +10 40.0 Cassiopeia (schedir)....+56 30 42.2 +11 15. 8 a Arietis BPersei (Algol)... NAME OF STAR a Leonis (Regulus). + 5 27+ 6 11.6 +18 9.6 aPiscis Australis.. Decimation On Meridian Upper. Lower. H. M. 0 1 H. M. +12 24+ 8 40.1 +20 38.1 - 10 42+11 56.5 +23 54.5 + 1938+12 47.5 +0 45, 5 +74 31 +13 27.5+1 25, 5 +27 113 49.71 47 7 26 1414 59. 32 57.3 +38 4217 9.35 73 +8 38 +18 21.46 194 +44 58 +19 18. 57 11. 5 +62 13 +19 51.57 49.5 045 +20 35.8 +8 33.9 30 5 +21 27.1 +9 25.1 +14 44 +21 34.7 +9 32.7 To find the time of the star's transit add or subtract, according to the sign, the numbers in the second column of figures to the date of the transit of the pole star given below. Thus, for a Andromeda February 1. Lower Transit of Polar Star is 4 h. 43 m. 35s. A. M., to which add 10 h. 40 m. and we have 3 h. 23 m. 35s. P. M.; for December 1, we find 7 h, 27 m. 51's. P. M., etc. APPROXIMATE PARALLAX AND DISTANCE IN LIGHT-YEARS OF SOME OF THE PRINCIPAL FIXED STARS. By light-years is to be understood the number of years light requires to travel from the star to us. The determination of stellar parallax is one of the most difficult and refined problems in practic:1 or observational astronomy. It is to find the angle which the semi-diameter of the earth's orbit subtends at the star-an angle always very small, as seen from the above table, and which cannot be measured directly, but by various processes too complicated to be explained here. Pole Star. MEAN TIME OF TRANSIT (AT WASHINGTON) AND POLAR DISTANCE OF POLARIS. From June 16 to August 1 both the upper and lower transits take place during daylight. The azimuth at the time of greatest Eastern or Western elongation can be easily computed from the formula: sin 4 = sin p where A denotes the azimuth. p the polar distance, and the latitude of the place. DATE OF GREATEST ELONGATION. To find the time of greatest Eastern or Western elongation, let II denote the hour angle, and and p as before, then we shall have And the hour angle in mean time is cos II tan p tan l. Hm II X 0.0664846. This quantity, H, added to or subtracted from the time of transit given above, according to the elongation required, will give the mean time of the greatest elongation at any place whose north latitude is l. Astronomical Phenomena for the Year 1913. ASTRONOMICAL SIGNS AND SYMBOLS. Mars. Conjunction. Opposition. Ascending Node. The Sun. The Earth. Two heavenly bodies are in conjunction" (6) when they have the same Right Ascension, or are on the same meridian, i, e., when one is due north or south of the other; if the bodies are near each other as seen from the earth, they will rise and set at the same time; they are in "'opposition" (8) when in opposite quarters of the heavens, or when one rises just as the other is setting. "Quadrature" (□) is half way between conjunction and opposition. By "greatest elongation" is meant the greatest apparent angular distance from the sun; the planet is then generally most favorably situated for observation. Mercury can only be seen with the naked eye at this time. When a planet is in its ascending" (2) or "descending'' (U) node it is crossing the plane of the earth's orbit. The term "Perihelion" means nearest, and "Aphelion" furthest, from the sun. An occultation" of a planet or star is an eclipse of it by some other body, usually the moon. In the year 1913 there will be five eclipses, three of the sun and two of the moon, as follows: 1. A total eclipse of the moon March 22, partly visible in the United States. 2. A partial eclipse of the sun April 6, visible in Alaska, British Columbia, Alberta, the northwestern portion of Saskatchewan, Washington, Oregon, Northern California and the northwestern portions of Nevada, Idaho and Montana. At Seattle the eclipse will begin at 8 hours 25.7 minutes A. M. and end at 9 hours 38.7 minutes A. M. The first contact will occur at 65° and the last at 11°.2 from the northern point of the sun's limb toward the West in both cases. 3. A partial eclipse of the sun August 31, visible only in Iceland, Greenland, Labrador, Newfoundland and the extreme eastern portions of Quebec, New Brunswick, and Nova Scotia. At St. Johns, Newfoundland, the eclipse will begin at 5 hours 33.2 minutes P. M. and end at 6 hours 9 minutes P. M. 4. A total eclipse of the moon September 15, visible partly in the United States as follows: 5. A partial eclipse of the sun September 29-30, visible only in Madagascar and the southeastern portion of Africa. PLACES. Boston.. Chicago... Denver. ASTRONOMICAL SIGNS AND SYMBOLS. Jan. Two heavenly bodies are in " conjunction'' (6) when they have the same Right Ascension, or are on the same meridian, i. e., when one is due north or south of the other; if the bodies are near each other as seen from the earth, they will rise and set at the same time; they are in "'opposition" (8) when in opposite quarters of the heavens, or when one rises just as the other is setting. "Quadrature" (□) is half way between conjunction and opposition. By "greatest elongation" is meant the greatest apparent angular distance from the sun; the planet is then generally most favorably situated for observation. Mercury can only be seen with the naked eye at this time. When a planet is in its "* 'ascending" (2) or "descending'' (U) node it is crossing the plane of the earth's orbit. The term "Perihelion ** means nearest, and "Aphelion'' furthest, from the sun. An occultation" of a planet or star is an eclipse of it by some other body, usually the moon. Charleston. Chicago.. Denver San Francisco. I.-ECLIPSES. In the year 1913 there will be five eclipses, three of the sun and two of the moon, as follows: 1. A total eclipse of the moon March 22, partly visible in the United States. Moon Total Total Moon M. M. H. H. 44 ** .. Mars. Enters Shadow. 2 D. H. M. 5 228 P. M. 5 10 26 P. M. 93 P.M. 11 521 A. M. 11 10 A. M. 13 4 P. M. 18 138 A. M. h 21 3 P. M. Ŏ 6 2.7 A.M. 44 S. 46'. 2 N. 13. 24 N. 47. in aphelion. 5 1.0 A.M. 5 44.4 A.M. unity. Conjunction. Magnitude 1.57. Moon's diameter 2. A partial eclipse of the sun April 6, visible in Alaska, British Columbia, Alberta, the northwestern portion of Saskatchewan, Washington, Oregon, Northern California and the northwestern portions of Nevada, Idaho and Montana. At Seattle the eclipse will begin at 8 hours 25.7 minutes A. M. and end at 9 hours 38.7 minutes A. M. The first contact will occur at 65° and the last at 11°.2 from the northern point of the sun's jimb toward the West in both cases. 3. A partial eclipse of the sun August 31, visible only in Iceland, Greenland, Labrador, Newfoundland and the extreme eastern portions of Quebec, New Brunswick, and Nova Scotia. At St. Johns, Newfoundland, the eclipse will begin at 5 hours 33.2 minutes P. M. and end at 6 hours 9 minutes P. M. 4. A total eclipse of the moon September 15, visible partly in the United States as follows: PLACES. H. M. H. M. H. M. H. M. After Moon Sets. After Moon Sets. After Moon Sets. " BA ** 44 5 33.0 A.M. 64 II.-PLANETARY CONFIGURATIONS, 1913. (Washington Mean time.) .. 5 25.5 A.M. unity. D. H. M. Jan. 29 3 A. M. h 12 6 5 A. M. 88 80 ** .. " 5 32.9 A.M. Magnitude 1.43. Moon's diameter 5. A partial eclipse of the sun September 29-30, visible only in Madagascar and the southeastern portion of Africa. gr. elong. E. 46° 43' O superior. |