60 CORRESPONDENCE ON ASTRONOMICAL ANNOUNCEMENTS. 



Coll'hs, 263). There Art. IV states distinctly: "The right ascension 

 and declination in the dispatch will be understood to give the position 

 (by proper motion approximately reduced) for the midnight following the 

 date of the dispatch, Washington time for American discoveries, Green- 

 wich time for European." 



If this be borne in mind, it seems unnecessary to burden the dispatch 

 by additional figures, indicating a local time. 



Still further, it seems unnecessary to add the daily motion in right 

 ascension. This, for the minor planets between Mars and Jupiter in 

 opposition, we know is always negative — the planets are retrograde — 

 and the numerical value of it will be in the neighborhood of 45^ or 50«. 

 Taking into account the distance from the equator, the position of the 

 ecliptic, and the motion in declination, a little reflection will easily 

 decide whether to assume a smaller or a larger value sufiBciently near 

 for knowing the run in a day or two. 



The request of giving with the right ascension also the second of time 

 assumes that the discoverer himself knows it, that he has followed up 

 the planet for at least 24 hours, and hence the motion has become known 

 to him with accuracy. But this is usually not the case, as on the other 

 hand it is desirable that the discoverer make the announcement im- 

 mediately after the first night. The daily motion, consequently, is con- 

 cluded from single comparisons extending perhaps over an hour, 

 whereby the unavoidable errors are multiplied by a factor greater than 

 24. The seconds added to the right ascension, therefore, would be only 

 illusory. 



When the nearest full minute is given, so that the uncertainty is ^ 

 minute, this seems indeed also sufficient for recognizing the planet. It 

 will be among the stars that are in a field of ]5', and by studying with a 

 little patience the configuration of these stars, the one searched for will 

 soon betray itself by its change of place. The apparent motion in right 

 ascension, in most cases, is far surpassing that in declination, so that 

 the inconsistency in giving the declination to a minute of arc and the 

 right ascension to a minute of time only is not so great as might seem. 

 Nevertheless, if found desirable, it is possible to narrow the limits of 

 uncertainty in the right ascension to one-sixth by the addition of only 

 one word more in the dispatch, giving the nearest round tenth number 

 of seconds. And this is the only alteration I should be willing to rec- 

 ommend in the form of the dispatch. 



To resume, I suggest, then : 



1. The local time (or its equivalent) is to be presented and looked for 

 as before, in conformity with Art. lY of the Smithsonian programme. 



2. To give the daily motion in right ascension seems superfluous. 



3. After the minute of right ascension to be inserted one of the words, 

 " ten," " twenty," " thirty," " forty," or " fifty," indicating the round tenth 

 of seconds (if no word follows, the second is understood to be zero). 



