THE ASTRONOMER Electronic Circular No 497 1991 Mar 19 20.59UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP, England. Telephone: (0256)471074 Int:+44256471074 Telex: 9312111261 Answerback: TA G JANET BOXES: GMH at UK.AC.CAM.ASTRONOMY.STARLINK or GUYH at UK.AC.SUSSEX.CLUSTER TELECOM GOLD: 10074:MIK2885 PRESTEL 256471074 ------------------------------------------------------------------- COMET MRKOS (1991k) On Mar. 17 Antonin Mrkos, Klet Observatory, reported his discovery of a rapidly moving object. Films taken at Palomar by E.Helin et al. show the object to be somewhat diffuse, and Mrkos later described the object as diffuse with central condensation. Available observations: 1991 UT R.A. (1950) Decl. m1 Observer Mar. 16.95628 12 44 29.36 - 2 47 07.9 15 Mrkos 16.97017 12 44 27.13 - 2 48 00.8 " 17.03753 12 44 16.12 - 2 52 20.0 15 " 17.04517 12 44 14.79 - 2 52 52.2 " 17.98406 12 41 43.03 - 3 53 58.3 " 17.99170 12 41 41.72 - 3 54 28.3 " 18.02642 12 41 35.98 - 3 56 38.7 15 " 18.03406 12 41 34.62 - 3 57 07.8 " 18.24219 12 41 01.86 - 4 10 45.1 14.0 Helin 18.27500 12 40 56.11 - 4 12 54.9 " 18.54028 12 40 11.89 - 4 29 53.9 15 McNaught 18.62014 12 39 59.01 - 4 35 07.3 13 Lowe 18.88368 12 39 13.86 - 4 52 14.0 " The following preliminary parabolic orbital elements are from 8 observations Mar. 16-18. The comet may be of short period. T = 1991 Mar. 20.992 ET Peri. = 181.852 Node = 1.941 1950.0 q = 1.55617 AU Incl. = 40.651 Ephemeris by Hurst based on a program by N.James: m = 13.0 + 5.0 log R + 10.0 log r Date R.A. (1950) Dec. R r Elong Mag. Motion h m o ' (AU) (AU) o "/hr P.A. 1991 Mar 19.00 12 38.93 -5 0.1 0.571 1.556 166.4 13.7 194 212 20.00 12 36.13 -6 5.9 0.569 1.556 167.4 13.7 195 213 21.00 12 33.28 -7 11.9 0.568 1.556 168.3 13.7 196 213 22.00 12 30.39 -8 17.9 0.567 1.556 169.0 13.7 197 213 23.00 12 27.47 -9 23.9 0.566 1.556 169.5 13.7 197 213 24.00 12 24.52 -10 29.7 0.566 1.557 169.6 13.7 197 214 25.00 12 21.54 -11 35.1 0.566 1.557 169.4 13.7 197 214 26.00 12 18.54 -12 40.0 0.567 1.558 169.0 13.7 196 214 27.00 12 15.53 -13 44.3 0.568 1.558 168.3 13.7 194 214 28.00 12 12.50 -14 47.9 0.570 1.559 167.4 13.7 192 215 29.00 12 9.48 -15 50.7 0.572 1.560 166.4 13.7 190 215 30.00 12 6.45 -16 52.4 0.575 1.561 165.2 13.7 188 215 31.00 12 3.43 -17 53.1 0.578 1.562 163.9 13.7 185 216 V418 CAS Further to the note on E493, Mike Collins, Sandy, reports that he has recorded the star on recent patrol photographs (K2415 film): 1991 Mar 13.8UT, 11.4; 14.9, 11.4. The star is probably red and may therefore be fainter visually. Close monitoring of this latest maximum is needed to establish whether this is a mira or nova-like variable, Guy M Hurst