Intelligence and Miscellaneous Articles. 323 



AN EPHEMERIS OF THE STARS PROPER TO BE OBSERVED WITH 

 MARS, AT THE ENSUING OPPOSITION OF THAT PLANET. 



[We. transfer the following to our pages, from the Supplement to 

 No. 11. of the Monthly Notices of the Astronomical Society, on ac- 

 count of the importance of the object contemplated by the Astronomer 

 Royal at the Cape, and in order to give additional publicity to the 

 Ephemeris itself. The latter is now given from October 11th to 

 November 7th ; and the corresponding portions for November and 

 December will appear in our Numbers for those months.] 



Previous to Mr. Henderson's departure for the Observatory at the 

 Cape of Good Hope, (to which he has recently been appointed Astro- 

 nomer, in the room of the late Rev. Fearon Fallows) *, he expressed a 

 wish that a selection might be made of such stars as would be proper 

 and convenient to be observed with Mars, at his ensuing opposition 

 in November next ; with a view to the determination of the parallax 

 of that planet ; and that a list of the same should be circulated 

 amongst different astronomers in various parts of the world, for the 

 purpose of obtaining corresponding observations. 



Mr. Sheepshanks having furnished the apparent places of Mars 

 (together with the semidiameter and horizontal parallax) for each day 

 during the requisite period, Mr. Baily selected the stats agreeably to 

 Mr. Henderson's wishes : and the Council of this Society, desirous of 

 promoting, as much as lies in their power, an object which, if actively 

 and properly followed up, may be attended with much advantage to 

 the science of astronomy, have caused the same to be printed and 

 circulated. 



The positions of Mars are the apparent geocentric places (cor- 

 rected for aberration) at mean midnight at Berlin ; deduced from the 

 Berlin Ephemeris, using 5th differences in the computation. The 

 positions of the stars also are their apparent places on the da)' of 

 transit: Mr. Sheepshanks having furnished the daily corrections for 

 precession, aberration, and nutation. These stars are selected in 

 such manner that there may always be a sufficient interval of time 

 between the transit of the star and the planet, to enable the observer 

 to read off the divisions of the circle or micrometer: except in a few 

 cases when they are both in the field of the telescope at the same 

 time, or so nearly on the same parallel that one setting of the instru- 

 ment will be sufficient for both observations, with the aid of a mi- 

 crometer. 



Mr. Henderson requests that, when both limbs of iJ/nrs. cannot be 

 conveniently observc(l on the same day, the northern limb should be 

 observed on the odd days, and the southern limb on the even days of 

 the month : as a guide to the observer, this is denoted by the letters 

 N and S inserted in the column of magnitudes. Also, that the transit 

 of the second limb should be observed prior to the day of opposition, 

 and the transit of the Jirst limb after that day : this is denoted by the 

 figures 1 and 2 annexed to Mars. 



* Sec our Number for September, jjp. 237, 24'-'. — Edit. 

 2 1' 2 



