Pe ey ee oe 
G. W. Hough on Cataloguing and Charting Stars. 171 
colored paper could be brought under the recording pen. This 
plan answered the purpose, but made it somewhat inconvenient’ 
to put our sheets on the cylinder. We therefore removed it and 
pen he desired, and this too without removing his eye from the 
telescope : 
This part of the apparatus is not shown in the drawings, but 
i i t. So far 
number of dots to indicate the magnitude, 
As fast as the stars enter the field of the telescope, they are 
Surface of the cylinder, so that when our observations are fin- 
ed, we have a perfect “fac simile” copy of the zone of stars 
observed. 
This apparatus we believe is the first which has been con- 
Cted to record accurately, by mechanical means, the Right 
Ascension and Declination at the same instant, or in other words, 
tomake a chart of the stars observed. When the dot is made 
on the cylinder, a record is also made on the working chrono- 
ope, which gives us the time to the hundredth part of a second. 
or the exact declination, an assistant reads the declinometer 
ale to the five-tenths of a second. Therefore, when o 
18 observed, we have not only a complete catalogue of the exact 
 4n case not read our declinometer scale, we can deter- 
mine the declination from the chart, within one-tenth of a min- 
ute of arc. The precision with which this machine will map 
0. - 
‘Stars is all that could be desired; since if two charts of the same 
Zone, made on different nights, be placed one over the other, the 
we will be superimposed so that the eye can detect no difference, 
_, BY means of movable adjustments, we can set the machine 
(having our sheet ruled for Right Ascension and Declination) 
$0 that it will give the position of the zone, at the beginning of 
the year, asthons sad error, For adjusting in Right Ascen- 
