iv Burnham: General Catalogue of Double Stars 
PART II. NOTES TO THE CATALOGUE 
In all cases where the stars have been reobserved since the observation recorded in Part I, a 
sufficient number of measures are cited, to show the motion, where there has been any relative 
change, and as far as possible its character, and to show the unchanged relation of the components 
where this seems to appear from the observations to this time. In many instances, and particularly 
of the Dorpat stars, where the observations extend over three-fourths of a century, perhaps the citation 
of a smaller number of measures would have answered every purpose, but it seemed best to give 
too many rather than too few. For obvious reasons only the best measures by the best observers 
are selected as a rule, and those made on a single night have been generally rejected except when 
there was nothing else in point of time to take their places. It must be clear to everyone that the 
omission of all indifferent and superfluous observations necessarily adds to the value and usefulness of 
this work. The author has not been handicapped or limited in any way as to space to be used; and in 
the citation of observations, and in the comments relating thereto, he has omitted nothing that in his 
judgment would be worth giving. It goes without saying that a large number of the published meas- 
ures of double stars should be rejected in any investigation or discussion as to the relative motion of 
the components. There need be no difficulty or hesitation in deciding as to the proper material to be 
used. If all the observations, good, bad, and indifferent, are employed in the computation of an orbit, 
it is certain that the value of the result will be correspondingly impaired, and no method of treating 
the doubtful material will prevent this. 
A liberal use has been made of diagrams to illustrate the motion shown by the observations. 
These are accurately drawn to scale with a protractor, devised for this purpose, having a 12 -inch 
circle and graduated arm, allowing the angles and distances to be laid down at the same time. The 
original drawing is then reduced to the proper scale in the camera, and the negative used to transfer 
the picture by contact to the block for engraving. These diagrams, therefore, may be taken as per- 
fectly representing the actual measures selected from the best available material. 
It will be apparent to anyone who will take the time to examine a sufficient number of pairs 
which were measured by the early observers, that as a rule these observations are very rough and 
more or less uncertain, and with errors too large to permit of their use in investigating the relative 
motion of the components. With the crude micrometers, driving-clocks, and equatorial instruments 
of the early part of the nineteenth century, and previous thereto, it is perhaps remarkable that the 
measures of that time are as good as they are, and it is doubtful if the astronomers of this day could 
do any better work with such tools. But there are too many instances where these early positions are 
known to be erroneous, or only very roughly approximate, to make it safe to rely upon them in fixing 
the position and limit of the apparent orbit of a binary system. The uniformly reliable and accurate 
measures of double stars begin with the work of the great Struve in his Mensurae Micrometricae. 
It is intended to give references to all the measures of each star, and to the more important 
papers relating to them. Doubtless some citations may have been overlooked, but it is not likely 
that many important omissions of this kind will be found. When there are no later observations, 
and the reference is brief, it is given in the last column of Part I. For this reason, many pairs which 
are likely to be of interest hereafter, are not represented by any note in Part II. 
In a general way the references to published observations may be said to end with those 
received early in 1906, but owing to the time required to pass Part II through the press, some of 
the series of measures printed in Astronomische Nachrichten, Monthly Notices, etc., are cited where they 
come in the later hours of right ascension. 
It will be seen that the micrometrical work on double stars since the observations of Struve 
has not been wisely distributed. A vast amount of time has been practically wasted in the duplica- 
tion of measures of prominent and familiar pairs, and in observing objects which need no attention 
except at long intervals. Much more would be known at this time of most of the double stars if the 
observing lists had been more carefully selected during the last sixty years. 
In order to make this portion of the work independent of the Catalogue (Part I) for general 
use and reference, the minutes and seconds of right ascension are given on the side, with the hour 
