279 V550 CYGNI (UGSS) Range: 14.2-~20 Position: 20 05 05.20 +32 21 21.6 (J2000, Yamaoka, vsnet-chart Magnitude: 5210) ID RA (2000) DEC X Y N V ERR B-V ERR a) Comparison star sequence 1 20 05 21.6 +32 20 59 211 -24 1 11.782 0.001 0.352 0.001 2 20 05 03.4 +32 21 56 -20 33 1 11.958 0.001 1.222 0.001 3 20 05 26.8 +32 19 33 276 -110 1 12.981 0.001 0.696 0.001 4 20 05 10.5 +32 22 30 70 67 1 13.921 0.002 0.860 0.004 5 20 05 09.8 +32 20 53 60 -30 1 14.083 0.002 0.843 0.004 6 20 05 18.0 +32 21 34 165 11 1 14.582 0.003 0.953 0.006 7 20 05 08.3 +32 20 31 41 -52 1 14.990 0.004 0.874 0.007 8 20 05 17.2 +32 21 41 154 18 1 15.188 0.004 0.745 0.008 9 20 05 07.1 +32 21 42 27 19 1 15.087 0.004 0.829 0.008 10 20 05 15.4 +32 23 49 132 146 1 15.514 0.005 1.032 0.012 11 20 05 05.8 +32 22 34 10 71 1 16.087 0.008 0.978 0.019 12 20 05 04.8 +32 21 24 -2 1 1 16.951 0.020 1.338 0.060 b) Wide-colour extension for CCD calibration 20 05 13.9 +32 19 19 113 -124 1 11.999 0.001 0.427 0.001 20 04 45.5 +32 26 46 -246 323 1 14.211 0.002 1.987 0.009 20 05 09.3 +32 22 01 54 38 1 14.394 0.002 2.512 0.016 Notes: 1. There are five additional bright stars in this field with accurate Tycho-2 photometry: 20h 04m 36.2 +32d 13' 07" 5.66+/-0.01 20h 05m 07.0 +32d 16' 00" 9.34+/-0.02 20h 04m 48.5 +32d 16' 34" 10.20+/-0.04 20h 04m 48.9 +32d 21' 38" 10.25+/-0.04 20h 04m 40.2 +32d 20' 41" 10.51+/-0.05 2. This preliminary single night sequence is expected to have errors of +/-0.02 mag. 3. The variable is the easternmost of a triple of stars running roughly in a line southeast to northwest. The middle star is the brightest and is star #10 of this sequence at magnitude V=16.95. The second brightest star lies 4 arcsec northwest of star #10 and is approximately magnitude V=18. V550 Cyg lies 3 arcsec east-southeast of star #10 and is about magnitude 20 in quiescence. 4. With a amplitude of over 5 magnitudes this variable is probably type UGSU. Bruce Sumner 22 April 2002