Jl-ly, 1911. 



KNOWLEDGE. 



275 



Jupiter appears as a brilliant star looking S.S.W". at sunset. 

 The planet sets at 0.42 a.m. on the 1st. and at 10.40 p.m. on 

 the 31st. 



For small telescopes this is the easiest and most interesting 

 planet to observe, on account of his brightness, numerous 

 moons, the markings on the disc and polar flattening. A 

 telescope mai^nifying about fifty times shows the planet of the 

 same apparent diameter as the moon seen with the naked eve ; 

 with this magnification and an aperture of two inches, the belts 

 may be seen, but the moons, when not too near the planet, 

 may be seen in any good pair of field glasses. 



The equatorial diameter of the planet on the 25th is 37", 

 whilst the polar diameter is 2" -4 smaller: this polar flattening 

 is readily observed in telescopes powerful enough to see the 

 belts. If sufficient magnification be used, the Great Red Spot 

 on the belts may be seen, and the period of rotation deduced. 

 This is verv short, and accounts for the oblateness, being 

 only 9'^ 55". 



The following table gives the Satellite phenomena : — 



"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 9.30 p.m.. are as follows : — 



The circle (C represents Jupiter : signifies that the 

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

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

 the Satellites. 



S.-\TURN : 



Saturn rises E.N.E. on Jtily 1st at 1 a.m., and on .A.ugust 

 1st at 11.5 p.m. The planet is situated in Aries, and will be 

 more favourably placed for observation during the next few 

 months than he has been for many years past. 



The ring, as seen in the telescope, appears well open, the 

 apparent diameter of the outer major axis being 40". and of 

 the outer minor axis 15"; the southern surface of the ring is 

 visible, and inclined to our line of vision at an angle of 22°. 



Uranus : — 



Uranus rises in the S.E. at 9.20 p.m. on July 1st and at 

 7.12 p.m. on August 1st. The planet is in opposition to the 

 Sun on the 21st. hence about this date he appears due South 

 at midnight ; he is describing a retrograde or westerly path, 

 about 2^ S.E. of <r Capricorni and can just be discerned with 

 the naked eye on a very clear night. The planet's remarkable 

 spectrum of broad dark bands is well worth the attention of 

 observers, even though they possess only small instruments. 



Neptune: — 



Xeptune is Hot observable this month, being in conjimction 

 with the Sun on the 14th. 



Meteor Shower. — The most notable shower in July is 

 that of the S Acjuarids. which occurs on the 28th. The radiant 

 is situated in R.A. ZZ'^ 36"', Dec. S. 11". and the meteors are 

 slow, with long tails. 



The Perseid shower also commences about the 10th. the 

 radiant being initially near o Cassiopeiae. 



Mira lo Cetil was due at maximum on June 30th, but as 

 the exact date is somewhat uncertain, observations of magni- 

 tude should be made for some time after this date. The mean 

 period is about 331 days. The star is also remarkable for 

 its spectrum, which may be well observed in a three-inch 

 telescope, using a Maclean or Zollner spectroscopic eyepiece ; 

 the spectrum consists of broad dark bands, in which bright 

 lines, due to hydrogen, occur. 



TELESCOPIC Objects (Double Stars, &c.l : — 5 Serpentis. 

 XV." 13"", X. 2° 13'. mags. 5-1, 10; separation 10". 



(i Serpentis. W." 41"'. N. 15° 44', mags. 3-8, 10; separation, 

 31". 



f> Serpentis. XVIII." 51'", X. 4= 4'. mags. 4-0. 4-2; separa- 

 tion. 21"- 6. Both are yellow, the primary being paler than 

 the smaller star. 



t Cephei XXII.'' 1'", X. 64' S'. mags. 4-7. 7 ; separation, 

 6". 



Cephei XXII.'' 26". X. 57° 57'. mags. 4-2. 7; separation. 

 40". .A pretty pair for small telescopes, stars respecti%ely 

 yellow and blue. It is also a typical short period variable 

 star, not of the Algol type, the period being 5'' 9''. with a sharp 

 rise from minimum to maximum in 1'' 9|''. 



Cluster in Libra. M 5. A compact cluster situated about 

 one-third of a degree North of the double star 5 Serpentis ; it 

 appears like a large nebulous .star when viewed with a pair of 

 opera glasses. 



Cluster in Serpens, N.G.C. 6633 ; about one-third of the 

 way from Serpentis to a Ophiuchi. The cluster is visible to 

 the naked eve. 



