Reports from Geisei Observatory<May 30, 2000>

• C/1999 S4(LINEAR)
LINEAR seems to have brightened considerably. It was at magnitude 11.3 in the 20cm refractor at 40x at 3:30 am on May 30. The 60cm reflector took this photo with a 6-minute exposure. The coma was much firmer than when it had been visible in the evening sky early in spring.

A fan-shaped tail extending to the west is visible in negative photos.

  C/1999 S4(LINEAR)
  2000UT        RA            decl          m1
  May 29.76858  2h04m41s.96  +31° 53'00".9  10.7

The photographic magnitude of this comet was on the brighter side compared with the GSC magnitudes. The above position of the comet has not been officially reported to
the Smithsonian. Geisei's observation data announced on my HP are available to anybody for orbital calculation and other purposes. However, the accuracy of data not reported to IAU is not guaranteed 100%. The margin of error in measurements obtained from this photograph is about ±1". I am a little worried about its accuracy because of its rather large coma.

Photograph 1
C/1999 S4(LINEAR)
6-minute exposure on 6415 film developed by D-19 for 5 minutes
60cm reflector at Geisei Observatory
Trimmed to about 60% of the original

• C/2000 K1(LINEAR)
In late May C/2000 K1 and K2 were discovered, as expected, by the LINEAR projects. Both were observed at Geisei on May 28 and 29. Photograph 2 is an image of K1 obtained with a 10-minute exposure on May 28. The magnitude was about 16.5. K2 was slightly fainter at 17.5. It appears to have a slight tail in the south but may be difficult to see it in the photograph. The following is the orbit of K1 calculated by Mr. Okamura and reported at his web site.

    T = 1999 Dec. 14.5694 TT
    q = 6.275731 AU
    e = 1.002099
    Peri    15.7955
    Node    260.1973 (2000.0)
    Incl    116.7884

The above data show that the orbit is hyperbolic with eccentricity larger than 1. This comet will not brighten, as it has already passed perihelion in December. Observation data obtained at Geisei will be reported in the next edition.

Photograph 2
C/2000 K1(LINEAR)
10-minute exposure on May 28.
60cm reflector at Geisei Observatory

The central part of the photograph is enlarged.