.\i'GrsT, 1911. 



KNOWLEDGE. 



295 



observation for a few hours after stinset, as he sots W.S.W". 

 at 9.28 p.m. on the 20th. On account of increased distance 

 from the earth, the apparent diameter is diminishing, the 

 equatorial diameter on the 20th being 34". whilst the polar 

 diameter is 2" -2 smaller. 



The Moon appears near the planet on the evenings of 

 the 1st and 29th. 



Only few satellite phenomena are observable on account of 

 Jupiter appearing in a bright part of the sky; these are as 

 follows : — 



"Oc. D." denotes the disappearance of the Satellite behind the disc, and 

 " Oc. R." its reappearance : " Tr. I." the ingress of a transit across the disc, and 

 "Tr. E." its egress ; " Sh. I." the ingress of a transit of the shadow across the disc, 

 and "Sh. E." its egress; 'Ec. D." denotes disappearance of Satellite by Eclipse, 

 and " Ec. R." its reappearance. 



The configurations of the Satellites as seen in an in\erting 

 telescope, and observing at 8.30 p.m. are as follows : — 



The circle (Q) represents Jupiter; O signifies that the 

 Satellite is on the disc ; • signifies that the Satellite is behind 

 the disc or in the shadow. The numbers are the numbers of 

 the Satellites. 



S.\TURN : — 



Saturn rises on the 1st at 11.5 p.m. and on the 31st at 

 9.15 p.m. ; each week he becomes more favourably placed for 

 observation. Towards the end of the month the planet may 

 be observed looking North of East at 10 p.m. a few degrees 

 above the horizon ; he appears as a bright star shining with a 

 leaden hue. The telescopic view of the planet is e.xtremely 

 fine on account of the ring encircling the planet, and a good 

 view may be obtained in small telescopes of about two inches 

 aperture, if the object glass is good and the instrument is held 

 steady. A magnifying power of about fifty is sufficient to 

 show the ring, but a greater magnification is required to see 

 the belts on the disc, as they are not so conspicuous as those 

 on Jupiter. The ring appears well open, the plane of the ring 

 being inclined to our line of vision at an angle of 22" ; the 

 southern surface is visible. The diameters of the outer major 

 and minor axes of the outer ring are 43" and 16" respectively, 

 whilst the polar diameter of the ball is 17". The planet is 



stationary on September 3rd. after which his motion is 

 retrograde or westerly The planet is in quadrature on the 

 13th. The Moon appears near the planet on the morning 

 of the 17th. 



Ur.^nus: — 



Uranus though somewhat low down in the sky, is well 

 placed for observation during the early evening, the planet 

 being due South on the 15th at 10.21 p.m. He is situated 

 about 2' S.E. of a Capricorni. Uranus is just perceptible to 

 the naked eye, but can easily be seen with a pair of opera 

 glasses. The diameter of the disc is nearly 4", and the colour 

 is greenish. As seen in large telescopes the planet appears 

 more luminous at the centre of the disc than at the limb — 

 somewhat similar to Jupiter and Saturn. The planet has a 

 fine spectrum containing broad dark bands. 



Neptune does not rise till 3 a.m. on the 1st August and 

 1 a.m. on September 1st; thus for all practical purposes the 

 planet is unobservable. 



Meteors : — 



The Perseid shower lasts nearly all the month, the earth 

 encountering the densest portion of the swarm about the 

 1 1th ; the radiant then being near v Persei. The meteors are 

 <|uick with yellowish streaks. 



Minima of .sMgol occur on the 7th at 11.40 p.m.. the 10th 

 at cS.30 p.m., and the 30th at 10.20 p.m. The period is 

 2"* 20'' 49""., from which data other minima may be calculated. 



Telescopic Objects : — 



Double St.\rs. — Polaris, mags 2- 1. 9-5 ; separation lS"-6. 

 The N'isibility of the small star is used as a test for a good 

 2-inch object glass. 



<T Scorpii. R.A. 16''15"': S.25'23': mags. 3-0, 7- 6 : separa- 

 tion 20" -6. 



j- Sagittae, R.A. 19" 45": N. IS' 54'; mags. 5-7, cS.S ; 

 separation 9"-0; colours, white and blue. 



a', a- Capricorni, R.A. 20" li"; S. 12° 50': mags, a' 4-5 

 a" 3-8 ; naked eye double: separation 373"; very easy with 

 opera glasses. 



7 Delphini, R.A. 20" 42'°; N. 15= 46'; mags. 4-1. 5-0; 

 separation 10"- 8; very pretty double for small telescopes; 

 colours, orange and light green. 



Nebula, &c. — Dumb Bell nebula in Vulpecula, nearly 4^ 

 due North of 7 Sagittae. Rather faint object in a 3-inch 

 telescope. 



(MSI Cluster in Sagittarius ; large luminous field of small 

 stars : fine object in a pair of field glasses, .\boiit a degree 

 E. of the star 4 Sagittarii. 



