THE FACE OF THE SKY FOR SEPTEMBER. 



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



Table 31. 



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



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



ctjuatorial zone, L-, to the temperate zones. Ti T. are the times of passage of the two zero meridians across the centre of the 



disc; to find intermediate passages apply multiples of 9" SOi", 9" 55*"" respectively. 



The letters ni, c stand for morning, evening. The day is taken as beginning at midnight. 



The Sun moves South pretty rapidly. Sunrise during 

 September changes from 5-13 to 5-59; sunset from 6-47 to 

 5-41. Its semi-diameter increases from 15' 53" to 16' 0". 

 The autumnal Equinox is passed 23'' 10'');;. 



Mekcurv is a morning star, well placed for observation 

 earlv in the month. On September 1st, one-fifth of disc is 

 illuminated, semi-diameter 4i"; on September 30th, the disc 

 is fully illuminated, semi-diameter 2i". 



Venus is an evening Star, but too near the Sun for 



convenient observation. lUuniination nearly complete, semi- 

 diameter 5l". 



The Moon.— Last Quarter 4" 1" 2y"c ; New ll"" 3" 48'";;; ; 

 First Quarter IS'' 1^ 55"";;;; Full 26" ll*" 34'°;;;. Perigee 

 9'' b^e. semi-diameter 16' 37"; Apogee 21'' 8''t', semi-diameter 

 14' 46". Maximum Librations, September 3'', T E., &^ 7° S., 

 IS** 7° W., 20'' 7° N. The letters indicate the region of the 

 Moon's limb brought into view by libration. E. W. are with 

 reference to our sky, not as they would appear to an observer 

 on the Moon. 



Table 33. Occultations of stars by the Moon visible at Greenwich. 



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



The asterisk indicates the day following that given in the date column. 



313 



