4i8 



KNOWLEDGE & SCIENTIFIC NEWS. 



[April, 1906. 



The Face of the Sky for April. 



By \V. Shackleton, I'.R.A.S. 



The SfN. — On the ist the Sun rises at 5.39 and sets at 

 6.30; on the 30th he rises at 4.37 and sets at 7.18. The 

 equation of time is negligible on i6th, hence this is a 

 convenient date for the adjustment of sundials. 



Sunspots and faculrc are usually conspicuous on the 

 solar disc, whilst recent spectroscopic observations of the 

 limb have shown many prominences. 



The position of the Sun's axis, equator, and helio- 

 graphic longitude of the centre of the disc is shown in 

 the following table : — 



The Moon : — 



Occult ATioNS. — The following are the occultations 

 of the brighter stars visible at Greenwich before mid- 

 night • — 



The Planets. — Mercury (April i, R.A. oh 58"; 

 Dec. N. 9° 42'. April 30, R.A. o'' 51™ ; Dec. N. 2°"32') 

 is in inferior conjunction with the Sun on the 5th and 

 hence unobservable at the beginning of the month ; to- 

 wards the end of the month the planet is a morning star 

 in Pisces. 



Venus (.\pril i, R.A. 1^ 24"! ; Dec. X. 7" 51'. 

 April 30, R.A. 3^ 43'"; Dec. N. 19° 57') is an evening 

 star in Aries, setting about an hour after the Sun on the 

 1st and about two hours after on the 30th. The apparent 

 diameter of the planet is io"-6, and 0-97 of the disc appears 

 illuminated. 



Mars (April i, R.A. 2'' 33" ; Dec. N. 15° 18'. April 30, 

 R..\. 3'' 56m; Dec. N. 20" 56') is an evening star in 

 Taurus, setting about 9.25 p.m. throughout the month. 

 The planet may be observed shortly after sunset looking 

 a little north of west, but he does not appear very bright. 



as he is at a point in his orbit situated at a great distance 

 from the earth. 



Jupiter (April i, R.A. 4i> 7m ; Dec. N. 20° 22'; April 30, 

 R.A. 4I' 32™ ; Dec. N. 21° 26') is getting more to the 

 west, and is only available for observations for a few 

 hours each evening ; about the middle of the month the 

 planet sets about 10.45 P-m- 



The equatorial diameter of the planet on the 14th is 

 34"'6, whilst the polar diameter is 2"-2 smaller. 



The following table gives the satellite phenomena 

 observable in this country : — • 



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

 "Oc. R." its re-appearance ; " 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 acrofs 

 the disc, and " Sh. E." i'.s egress. 



Saturn (April i,R.A. 22h47m; Dec. S. 9'' 26'. April 30, 

 R.A. 22h 58m ; Dec. S. 8 ' 25') is a morning star in Aqua- 

 rius, rising about 4 a.m. near the middle of the month. 



Uranus (April 15, R.A. i8h 37^; Dec. S. 23° 28') 

 does not rise until after midnight ; he is situated low 

 down in Sagittarius. 



Neptune (April 15, R..\. 6*^ 34™; Dec. N. 22" 19') is 

 on the meridian before sunset, but is observable in the 

 west until midnight ; near the middle of the month the 

 planet sets about i a.m. 



Meteor Showers : — 



Minima of Algol may be observed on the nth at 

 11.33 P-'f-i and on the 14th at 8.22 p.m. 



Telescopic Orjects: — 



Double Stars. — 7 Virginis, XII.^ 37"", S.o^ 54', mags. 

 3, 3 ; separation ^"-g. Binary system ; both components 

 are yellow, though one is of a deeper hue than the other. 

 An eyepiece of a power of 30 or 40 is required on a 3-in. 

 to effect separation. 



s- Bootis, XI\'.h 36"°, N. 16" 53', mags. 4, 6; separa- 

 tion 6". Requires a power of about 40. 



e Bootis, XIV." 41", N. 27'' 30', mags. 3, 6i ; separa- 

 tion 2"-6. Very pretty double, with good colour contrast, 

 the brighter component being yellow, the other blue 

 green. 



J Bootis, XIV.'' 47™, N. 19° 31', mags. 5, 7; separa- 

 tion, 2"-4. Binary; one component being orange, the 

 other purple. 



Clusters.— M 3 (Canes Venatici), XIII.'' 38", N. 28° 

 48'. This object, though really a globular cluster of 

 myriads of small stars, appears more like a nebula in 

 small telescopes. It is situated between Cor Caroli and 

 Arcturus, but rather nearer the latter. 



