Visibility II / V
1585 Union (1929 DB, 1937 QF, 1939 CD1,1944 DG, 1947 RG, 1949 EE, 1952 QA1,1952 SD) The asteroid on the outer edge of the main zone was imaged on the second night of the September 2021 work. The asteroid was discovered by South African astronomer Ernest Leonard Johnson at the Johannesburg Observatory (078) on September 7, 1947. Ernest Johnson has found a total of 18 asteroids and comets C / 1935 A1, C / 1948 R1, C / 1949 K1, 48P / Johnson. source Wikipedia
https://en.wikipedia.org/wiki/Ernest_Leonard_Johnson . The asteroid is named after the Union Observatory in Johannesburg, South Africa. Source Wikipedia https://en.wikipedia.org/wiki/Union_Observatory . The size of the large asteroid is 55.27km and the rotation speed is 12.798h / r.
Spectral class spec_T => P or C dark carbon? In 1929, the asteroid was first identified as a 1929 DB in Ucclen, Belgium
observatory. The first recorded observations start at the Finnish Turku Observatory in February 1939. Source Wikipedia
https://en.wikipedia.org/wiki/1585_Union . When photographed, the asteroid was 3,514au at a distance and 2.85au closest on June 11, 2021.
1Picture. first image in the series1 L30s measured, 2021-09-04UT 18: 26: 22UT 2459462.26831JDUT 16h44m50.0s + 02d16'44.5 "16.616mag Std Dev 125.725 SNR5.559 FWHM3.333", JPL Horizon 18: 26: 22UT 16h44m50.0s + 02d16'43.9 "16.763 mag.
2Picture. last image in the series20 L30s measured, 2021-09-04UT 18: 37: 37UT 2459462.27612JDUT 16h44m50.15s + 02d16'40.4 "16.496mag Std Dev 85.527 SNR4.520 FWHM5.016", JPL Horizon 18: 37: 37UT 16h44m50.22s + 02d16'39.9 "16.763 mag.
3Picture sum view of L30s 1-20 image stack, motion not displayed. There are no other asteroids below 22.3 mag in the picture. TYC 387-534-1 v. 11.70mag stars used for calibration of brightness measurement.