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Thu, 01 Apr 2004 - C/2004 F4 (Bradfield)

The veteran Australian observer, Bill Bradfield, has done it again! He has beaten all the professional search teams and found a relatively bright comet, though at the moment it is too close to the Sun for observation. Although he made the initial discovery with his 0.25-m reflector on March 23.43, it took several weeks to get full confirmatory observations. On discovery it was 8th magnitude, but had brightened to 5th magnitude by the time it was confirmed on April 8. Bill had been hunting for comets in the twilight sky in the hope of finding a bright sungrazer, and whilst this one isn’t a member of the Kreutz group, it will be impressive as it passes through the SOHO field later this week.

The preliminary orbit, which puts perihelion at 0.17 AU on April 17, suggests that it should have been a relatively bright object during the winter and well placed in northern skies, so it is a little surprising that no-one picked it up. Perhaps it will be found in archival images, which should lead to an immediate improvement in the orbit. Alternatively the comet may have undergone an outburst, in which case its future behaviour becomes uncertain.

On the basis of the initial rough orbit, it was due to enter the Soho satellite's C3 coronagraph field on April 16 and leave it on April 20. Its elongation from the Sun rapidly increases and UK observers should be able to pick it up as a 4th magnitude object in the morning twilight on April 23. It remains a binocular object in the morning sky until June, passing through Pisces and Andromeda and is close to M31 in the second week of May. The orbit should be improved once the comet is observed as it passes through the SOHO field, so more details and finder charts will be issued in a week’s time. It may well be worth getting up early at the end of the month as there may be three comets on view – 2003 T3 (Tabur) lies 5° below Bradfield’s comet, whilst 2002 T7 (LINEAR) is on the eastern horizon. An updated ephemeris for Bradfield given below.

Jonathan Shanklin

   Ephemeris and orbital elements from IAU Circular 8326:

    T = 2004 Apr. 17.129 TT          Peri. = 333.298
                                     Node  = 222.992   2000.0
    q = 0.16749 AU                   Incl. =  63.118

2004 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    Mag
Apr. 20     1 24.29   +14 20.3   0.837   0.205    7.4  140.9    2.5
     25     1 03.97   +25 36.5   0.938   0.345   20.1   91.1    4.4
     30     0 59.13   +32 24.5   1.067   0.491   27.2   69.6    5.8
May   5     1 00.16   +37 00.6   1.190   0.627   31.8   58.0    6.9
     10     1 03.54   +40 28.2   1.302   0.754   35.3   50.7    7.7
     15     1 07.85   +43 15.8   1.405   0.874   38.2   45.7    8.3

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