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Date: Fri, 22 Nov 1996 18:34:25 -0800
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Subject: Report observing project N21
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Report for Astronomy On-line
Observing project No 21
Comet Group, Varna, Bulgaria

Investigation of the Comet Hale-Bopp

The new Comet Hale-Bopp is an exceptionally interesting object for the
professional and amateur astronomers. The Comet Group from the Astronomical
Observatory & Planetarium "N. Copernicus" in Varna carry out visual and
photographic observations, as well as observations using CCD, since August
1995. In September, October and November 1996, during the active period of
Astronomy On-Line 24 visual observations of the comet were made. The results
are presented in following table:

Date (UT)        m   RF  Ap PWR  D(') DC   Obs.
1996 9  01.75   6.7  SC  B  10   12   5    AND03
1996 9  02.77   5.5  SC  B  10    9   5    RAD01
1996 9  02.89   6.8  SC  B  10             AND03
1996 9  07.87   6.7  SC  B  10    9   4    AND03
1996 9  08.87   6.6  SC  B  10    9   4    AND03
1996 9  09.90   6.6  SC  B  10    9   4    AND03
1996 9  10.86   6.5  SC  B  10    8        AND03
1996 9  10.76   6.3  SC  B  10    8        RAD01
1996 9  11.75   6.5  SC  B  10    8   5    RAD01
1996 9  11.81   6.6  SC  B  10    8   5    AND03
1996 9  15.73   6.5  SC  B  10        5    RAD01
1996 9  15.74   6.5  SC  B  10        3    AND03
1996 9  16.74   6.3  SC  B  10    8   5    AND03
1996 9  17.88   6.6  SC  B  10    8        AND03
1996 9  24.88   6.4  SC  B  10    9   5    AND03
1996 9  30.86   6.3  SC  B  10    9   4    AND03
1996 10 15.79   5.9  SC  B  10        4    AND03
1996 10 18.78   5.9  SC  B  10    9   4    AND03
1996 11  8.86   5.3  SC  B  10        4    AND03
1996 11 11.77   5.1  SC  B  10        4    AND03
1996 11 17.76   5.6  SC  B  10        4    RAD01
1996 11 17.77   5.6  SC  B  10        4    RAD01
1996 11 20.75   5.5  SC  B  10        4    RAD01
1996 11 20.76   5.5  SC  B  10        4    RAD01
Date - time of the observation
m - visual magnitude
RF - reference star catalogue
ap - aperture
PWR - magnification
D - diameter of the coma in arcminutes
DC - degree of condensation (0 - completely diffuse object, 6 - prominent
     starlike core, 9 - starlike comet)
RAD01 - Veselka Radeva
AND03 - Krasimir Andreev
Based on 83 visual estimates of the comet's brightness made from April 1996
till now we obtained a funcion describing how the comet's magnitude (m) changes
with its distance to the Sun (r) and to the Earth (Delta):
m = Hy + 5*lg(delta) + y*lg(r)
Hy is the comet's absolute magnitude, y characterizes the change of the comet's
brightness as the comet approaches the Sun
According to our data:
m = -1.1 + 5*lg(delta) + 9.14*lg(r)
A lightcurve was plotted. No bursts were registered.
On 15.11.1996 a photograph of the comet was taken with a Schmidt telescope
50/70 in the Natioal Astronomical Observatory - Rojen, Bulgaria (1750m height
above the sea level, at UT = 17h 05m 09s, 5 min exposure, astroplate ZU-21
(Comfig1.GIF).
The astronomers of the National Astronomical Observatory and Institute of
Theoretical Astronomy (Bulgarian Academy of Science) Tashko Valchev, Albena
Ivanova and Asya Cvetcova gave us two images of the comet taken by CCD-ST6
using the 2m telescope (Comfig2.GIF, Comfig3.GIF). They show
a the double comet's tail and jet directed to the Sun (may be an anomalous
tail is developed?).
We are thankful to the observatories in Slovenia and the UK where images of the
comet were taken for us. Unfortunately due to communication problems we could
not download them.

Astronomical Observatory & Planetarium "N.Copernicus", Varna, Bulgaria
ASTRO@MS3.TU-VARNA.ACAD.BG
22.11.96