THE ASTRONOMER Electronic Circular No 456 1990 Oct 28 09.44UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP, England. Telephone: (0256)471074 Int:+44256471074 Telex: 94082518 Answerback: TAGUY Microlink: MAG60138 JANET:GMH @ UK.AC.CAM.ASTRONOMY.STARLINK GUYH@UK.AC.SUSSEX.CLUSTER TELECOM GOLD: 10074:MIK2885 PRESTEL 256471074 -------------------------------------------------------------------- ROSAT MISSION *Objective* Further to the announcement on E455, further details of this major international PRO-AM effort have been finalised. The objective is to alert professional astronomers when selected cataclysmic variables start to rise from minimum so that they can be monitored by the x-ray survey satellite ROentgen SATellite (ROSAT). In addition these stars will be surveyed by IUE and various ground based observatories so that simultaneous monitoring at multiwavelengths can be achieved. *Target List* In addition to the 'high-priority' stars already mentioned, which require continuous coverage every clear night, other stars are to be observed but this list changes weekly. Circular E457, which will follow shortly, gives details of all stars to be covered from today until 1990 Nov 18 with the appropriate window for each star. In the list, 'y' appears under '1', '2' or '3' to signify the period the star is to be covered except for stars with 'yyyyyyy' which are the stars needing permanent monitoring. *Windows* Windows from now until 1990 Nov 18 are: Period 1 1990 Oct 29-Nov 4 Period 2 1990 Nov 5-Nov 11 Period 3 1990 Nov 12-Nov 18 *Charts* The data for each star is based solely on the information listed in GCVS4 (although I am aware there have been some changes since). Charts for the variables are given under 'TA', where the last revision date is given, or under 'BAA' with the chart reference. The following stars do not yet have charts but if anyone has one please send a copy to the Editor as soon as possible: AE Aqr; FO Aqr; V1101 Aql; V747 Cyg; V1060 Cyg; V1285 Cyg. In addition RU LMi does not yet have a sequence and V1504 Cygni needs improvement of star detail. For these eight stars prime focus photographs of the variable, and of a known sequence field are urgently needed - please consult the Editor if you can help. If anyone needs charts please e-mail. *Reporting* If any star is found to be rising from minimum please telephone Martin Mobberley on the numbers quoted in E455 (available all