550 



KNOWLEDGE & SCIENTIFIC NEWS. 



[September, 1906. 



The Face of the Sky for September. 



By W. Shackleton, F.R.A.S. 



The Sun. — On the ist the Sun rises at 5.12 and sets at 

 6,47; on the 30th he rises at 6.0 and sets at 5.41. 



The Sun enters the sign of Libra on the 23rd at 

 II p.m., when autumn commences. 



The equation of time for sundial purposes is negligible 

 on the I St and 2nd, hence these dates are convenient for 

 the adjustment of dials, as only the longitude correction is 

 needed. Sunspots may usually be observed on the 

 Solar disc, but there is a noticeable diminution both in 

 number and size, indicating that we are well past the 

 maximum. 



The positions of the Sun's axis, centre of the disc, and 

 heliographic longitude of the centre are given in the 

 following table : — 



The Moon : — 



Date. 



Sept. 



OccuLTATioNS. — The following are the particulars of 

 the principal occultations visible from Greenwich ; it 

 will be noticed that the ist magnitude star Aldebaran 

 suffers occultation on the morning of the loth : — 



The Planets. — Mercury (Sept. i, R.A. g^ 31™; 

 Dec. N. 15° 3' ; Sept. 30, R.A. i2*> 43-" ; Dec. S. 3° 38') 

 is in superior conjunction with the Sun on the 24th, and 

 hence is unobservable towards the end of the month ; 

 during the earlier part of the month the planet is a 

 morning star in Leo, and being near the point of greatest 

 elongation is favourably placed for observation. On the 

 gththe planet rises at 4.2 a.m., whilst on the 6th he is 

 situated about i" north of Regulus. 



Venus (Sept. i, R.A. 131^ 25m; Dec. S. 10° 28'; 

 Sept. 30, R.A. 15'' 16° ; Dec. S. 22° 13') is at 

 greatest easterly elongation of 46° 29' on the 20th. 

 During the month the planet moves from an apparent 

 position close to Spica on the ist to one in Libra on the 

 30th. As seen in the telescope the planet has the phase 

 of "half moon," 0-51 of the disc being illuminated. 

 On the 15th the planet sets at 7.25 p.m. 



Mars (Sept. i, R.A. 9" 43-" ; Dec. N. 14"^ 58' ; Sept. 30, 



R.A. 10'' 53 " ; Dec. N. 8" 26') is a morning star in Leo, 

 rising about 3.30 a.m. throughout the month. The 

 planet is in conjunction with Mercury on the morning 

 of the 5th, Mercury being 10' to the South. 



Jupiter (Sept. i, R.A. 6'' 26"^ ; Dec. N. 23° 2'; Sept. 

 30, R.A. 6'' 42m ; Dec. N. 22° 51') is a morning star in 

 Gemini, rising about 10.45 p.m. on the 15th. 



Saturn (Sept. i, R.A. 22'' 57™ ; Dec. S. 9° i' ; Sept. 30, 

 R.A. 22'' 49™; Dec. 

 S- 9° 50') is an evening 

 star describing a retro- 

 grade path in Aquarius, 

 and is well placed for 

 observation, being due 

 south at II p.m. on the 

 19th, when he rises 

 at 5.45 p.m. The planet 

 is in conjunction with 

 the moon on the morn- 

 ing of the 3rd, at 3 a.m. 

 — the Moon being "full." 

 As seen in this country, 

 the planet will appear 

 to be about 1° 15' from 

 the northern limb of the 

 moon, as shown in the 

 diagram. 



We are looking on 

 the northern surface of the ring, the outer major and 

 minor axes of which are 44" and 4" respectively, whilst 

 the apparent diameter of the ballis i7"'6. 



The planet is in opposition to the Sun on the 5th at 

 3 a.m., hence near this date he is on the meridian about 

 midnight. 



Uranus (Sept. 15, R.A. iS^ 20" ; Dec. S. 23° 41'), 

 though rather low down in the sky, is fairly well placed 

 for observation during the early evening, and is due 

 south shortly after sunset. The planet is situated in 

 Sagittarius in a part of the sky devoid of good reference 

 stars, though the star m Sagittarii is some 3° to the 

 N.W. 



The planet is at the stationary point on the 14th, after 

 which his motion is direct or easterly, whilst on the 28th 

 he is in quadrature with the Sun, and hence near this 

 date he crosses the meridian about 6 hours after the 

 Sun. 



Neptune (Sept. 15, R.A. 6'' 53"; Dec. N. 22° o') rises 

 about 1 1. 1 5 p.m. near the middle of the month, and 

 hence is not in a favourable position for observation 

 before midnight ; the planet is situated about 1° north of 

 the star j- Geminorum. 



Minima of Algol occur on the loth, at 10.4S p.m., and 

 on the 13th, at 7.37 p.m. 

 Telescopic Objects : — 



Double stars: ^ Ursse Majoris XIIL"^ 20™, N. 55° 25', 

 mags. 2, 4 ; separation, I4""4. 



s'Aquarii XXII. ^ 23'", S. o"^ 35', mags. 4, 4, separa- 

 tion 3"-2. Both components are yellowish, 



[i Cygni XlX.h 27", N. 27° 46' mags. 3, 5 ; separa- 

 tion 34". The brighter component is yellow, the other 

 blue ; very easy double in small telescopes with a power 

 of 20. 



Cluster (M 11) in Aquila or Antinous. R.A. 18" 45"° ; 

 Dec. S. 6' 23 . \'ery pretty object for 3 or 4 inch 

 telescope ; it is an easily resolvable fan-shaped cluster, 

 with an 8th magnitude star in apex and an open pair of 

 the same magnitude just outside it. 



(M 8) Cluster in Sagittarius ; large luminous field of 

 small stars ; fine object in pair of field glasses. About 

 a degree E. of the star 4 Sagittarii. 



