The sources

• ``Comet Light Curve Catalogue'' - CLICC - Kamél ([1991]). About half of the magnitudes included in this catalog have been taken from his compilation of cometary magnitudes). Kamél mainly used two sources for references:
• Astronomischer Jahresbericht for the period 1899-1968
• Astronomy and Astrophysics Abstracts for the period 1969-1989.
A large part of his data set comes from Green's ([1988]) Archive of Cometary Photometric Data. The ending date for
CLICC was Dec. 31, 1989.
 
• magnitude measurements from the Minor Planet Center (MPC) data base for the period Jan. 1, 1990 to August 1998
• A few extra observations that were not included in the MPC data base but appeared in the IAU Circulars or International Comet Quarterly. Data from a few papers devoted to particular comets, published after 1990, have also been included (Mueller [1992], Meech et al. [1993], Chen & Jewitt [1994], Lamy & Toth [1995], Mueller & Ferrin [1996], Lamy et al. [1996], Lamy et al. [1998a], Lamy et al. [1998b]) as well as our own set of nuclear magnitudes (Licandro et al. [1999a]).

From these data sources, we have taken: all the nuclear magnitudes and total magnitudes observed at heliocentric distances r > 3 AU observed after 1950.

Some considerations are presented in Sect. 3.3 to justify the deletion of some data. Table 1 presents a summary of the sources and a general classification of the data. The numbers listed correspond to the data remaining after the deletions mentioned in Sect. 3.3.
 
 

Table 1: Statistics of our data sets

Number of observations (1)	3990
Data taken from CLICC	1474
Data taken from MPC	2392
Data taken from other sources (2)	124
Observations pre-perihelion	1968
Observations post-perihelion	2022
Reported nuclear magnitudes (3)	1952
Total magnitudes at r > 3 AU (3)	1073
Scotti's total magnitudes at r < 3 AU (4)	514
Scotti's total magnitudes at r > 3 AU (4)	553
Scotti's nuclear magnitudes (5)	412
Roemer's magnitudes	700
CCD nuclear magnitudes (6)	312

⁽¹⁾ For consistency with other observers, the observations by J. Scotti reported as total but taken at r < 3 AU are not included in these numbers.
⁽²⁾ Observations taken from the ICQ after 1990 that did not appear in the MPCs (25), personal communication by C. Hergenrother (6), our own observations (48), data taken from the literature (45).
⁽³⁾ Observations by J. Scotti are not included.
⁽⁴⁾ Magnitudes reported as total.
⁽⁵⁾ Magnitudes reported as nuclear, in most cases Scotti has applied a coma reduction method.
⁽⁶⁾ Only the observations with medium and large aperture telescopes are included. This number may be underestimated, because for many observers we do not know which telescope was used.

2000-03-07