When planning the details of the observations for thc Eros campaign in August 1930, a special note was made tc remind us of the necessity of a scrutiny under higher power: than the eye-piece used for the measures (360 x ) on suck occasions as the definition would permit. The chief reason: for this precaution were the possibility of measuring thc diameter, of noting irregular form or surface detail, or ever duplicity, related to the known variation in brightness.
The suggestion that Eros is a double planet was to OUI knowledge first put forward by Ch. And& (AN 155.27), hi2 reasons being the similarity of the light-curve to that of a j 3 Lyrae variable. The observed Cbinge~ of thc enqdhded this variation with Eros' position in the sky lend supporl to this theory, the maximum amplitude corresponding tc the earth's passage through the plane of revolution.
The only visual observation of duplicity known to u: is by Innes and Wood in 1924 (AN 24r.55). It seems difficul to reconcile this with the results of the present opposition because of the facts that the geocentric distance at that timt was considerably greater, the planet much fainter, the telescopt only of 9-inches aperture and the night, as stated, not 5 good one.
On a few favourable occasions in December and Januar! the planet was scrutinised by us with the 26+-inch refractor
ASTRONOMISCHE NACHRICHTE
W. H. uan dm Bos and W . S. Finsen. using a power of 1070 x , but no conclusive evidence c m b e obtained, though occasionally the image seemed to be slightly elongated. This may have been real or due to atmospherical causes; the observers did not feel certain of any other conclusion than that the diameter was hardly greater than the diffraction-disk of a star of the same brightness and could not be measured. On the night of February 3-4, however, the image was certainly a figure-of-eight, resembling that of a motchede or nearly separated double star of about or18 distance. The direction of the elongation was measured. On the next night such measures were obtained over a period of &hours. These observations showed that the angle made a complete revolution in a -@Peri od of 5h17m, observations on later nights have confirmed this. No measures of distance were attempted, as they would not have been more reliable than (or even as reliable as) careful estimates, based on our experience of close double stars.
The following list gives the observations obtained here. It is hoped that they will be supplemented by others in different longitudes, such as the large American refractors, or Lembang, Java.
The following table is self-explanatory. Definition is recorded on the scale: 5 =excellent, o = very bad. The power used was 1070 x , except for 3 measures when 810 x was used, as noted in the accompanying remarks.