THE FACE OF THE SKY FOR JULY. 



By A. C. D. CROMMELIN, B.A., D.Sc, F.R.A.S. 



Table 41. 



Table 42. 



P is the position angle of the North end of the body's axis measured eastward from the North Point of the disc. B, L 



are the helio-(planeto-)graphical latitude and longitude of the centre of the disc. In the case of Jupiter, L x refers to the 



equatorial zone ; L 2 to the temperate zone ; Ti, T 2 are the times of passage of the two zero meridians across the centre of the 



disc ; to find intermediate passages apply multiples of 9 h 50i m , 9 h 55| m respectively. 



The letters m, e, stand for morning, evening. The day is taken as beginning at midnight. 



The Sun has now commenced his Southward march. 

 Sunrise during July changes from 3.49 to 4.23 ; sunset 

 from 8.18 to 7.49. Its semi-diameter increases from 15' 45" 

 to 15' 47". It is at its greatest distance from the Earth at 

 midnight on July 3rd. Outbreaks of spots in high latitudes 

 should be watched for. 



Mercury is an evening star, reaching East Elongation on 

 July 7th, when it is 16° from the Sun. Illumination one-half 

 on 1st, one twenty-fifth on 30th. Semi-diameter increases 

 from 3i" to 5i". 



Venus is a morning star, reaching West Elongation July 4th, 

 when it is 46° from the Sun ; 7?° South of Moon on 30th. 

 Semi-diameter diminishes from 12" to 9". At beginning of 



month one-half of disc is illuminated ; at end of month 

 five-eighths. Being South of Sun till the 24th, it is less well 

 placed for Northern observers than it was as an evening 

 star ; after that its position is favourable. 



The Moon.— New 4" 5 h 6 m m ; First Ouarter 10 d 9 h 37 m e ; 

 ■Full 18 d 6 h 6 m m; Last Quarter 26 d 9 h 59 m m. Perigee 

 6 d \2 h e, semi-diameter 16' 24". Apogee 22 d 7 h e, semi- 

 diameter 14' 46". Maximum Librations, l d 6° E, 3 d 7° S., 

 14 d 5° W., 16 d 7° N., 28 d 7° E., 30 d 7° S. The letters 

 indicate the region of the Moon's limb brought into view 

 by libration. E. VV. are with reference to our sky, not 

 as they would appear to an observer on the Moon. (See 

 Table 43.) 



Table 43. Occultations of stars by the Moon visible at Greenwich. 



From New to Full disappearances take place at the Dark Limb, from Full to New reappearances. 



225 



