ACTA ASTRONOMICA Vol. 43 (1993) pp. 177±181
The Orbit of the Minor Planet (7) Iris
by I. Wøodarczyk
Astronomical Observatory of the ChorzÂow Planetarium, 41-501 Chorz Âow 1, P.O. box 10, Poland.
Received December 17, 1992, ®nal version received in May 1993
ABSTRACT
30 precise positions from the ChorzÂow Observatory and 15 observations from 3 others obser- vatories of (7) Iris made in 1991 are used to determine the orbit of this minor planet. The orbit was determined using once the SAO Catalogue and once the PPM Catalogue. The latter orbit ®ts better to all the observations. Key words: Minor planets ± Astrometry
1. TheChorzow Observations
The photographic observations of (7) Iris were made with the photographic
camera 200 1000 mm attached to the refractor 300 4500 mm. The geographical
0 00
h m s
= = h = coordinates of this refractor are 1 15 58.52, 50 17 31. 8, 328 m.
The ORWO plates ZU-21 16 16 cm were measured with the coordinate measur- ing instrument Ascorecord E-2. For the reduction of these plates the Turner method with the complete second- order polynomial was used. On every plate 10 to 14 reference stars were chosen (together 50 stars were considered). The coordinates and the proper motions of
all stars were taken once from the SAO Catalogue for the epoch 1950 0 and once from the PPM Catalogue for the epoch 2000.0. Our positions of (7) Iris obtained with the SAO Catalogue are given in Table 1. There are observations made in 1991 during the opposition of (7) Iris in Nov. 15th, and published in the Marsden's Minor Planet Circulars (MPC) till 1992 Aug. 13th. There are 30 observations made in our observatory (Marsden code 553) and 15 observations from others observatories. The codes are: 46-Klet Observatory, 657-Climenhage Observatory, Victoria and
675-Palomar Mountain Observatory. Table 1 contains: number of observation, date of observation in UT, observed topocentric position and , referred to the mean epoch 1950.0, and the Marsden code of the observatory (MPC 19 348). All 178 A. A.
Table1
Observations of the minor planet Iris in Aug. 1991.