Equatorial coordinates (Right ascension and Declination)
are given for two equinoxes 1950 (Besselian coordinates *al*1950, *de*1950) and
2000 (Julian coordinates *al*2000, *de*2000). Most of published coordinates
are B1950 coordinates. Conversion to J2000 has been made according to the
"Merits Standards" published in the U.S. Naval Observatory Circular (1983).
For computer use, coordinates are expressed as decimal values
(hours to 0.00001 and degrees to 0.0001 for Right Ascension and Declination,
respectively).
The standard deviation of coordinates is generally not known. Thus we
are using a flag *ipad* to tell if the standard deviation is smaller than
10 arcsec or not. We collected systematically accurate coordinates in
literature (see Paturel et al. 1989). Recently, we added accurate coordinates
directly obtained from images stored in LEDA (Paturel et al. 1996)
and from COSMOS database (Rousseau et al. 1996).
Among the 100872 galaxies 69165 have accurate coordinates (69 percent).

Galactic coordinates *l*2, *b*2 are calculated (in degrees to )
from *al*1950 and *de*1950 using the coordinates of the galactic pole
*al*1950(pole) = 12.81667 *de*1950(pole) = 27.4000 and
the coordinates of the origin *al*1950(origin) = 17.70667 *de*1950
(origin) = -28.9167
according to Blaauw et al. (1960). These galactic coordinates are
used to estimate the galactic extinction *ag* converted to Burstein-Heiles
system (Burstein & Heiles 1984) from the relationship given in the
Second Reference Catalog (de Vaucouleurs et al. 1976;
p32, rel. 22; hereafter RC2). In fact, for galactic latitude the
difference between both systems is negligibly small (except for the zero
point difference of 0.20 mag due to the fact that Burstein-Heiles give
no absorption at the galactic pole).
In Fig. 1 (click here) the difference between *ag* from RC2 and from
Burstein-Heiles is plotted vs. the galactic latitude.

**Figure 1:** Difference of galactic extinction from RC2 and
Burstein-Heiles vs. the absolute value of the galactic latitude

The conversion from RC2- to BH-system is the following:
if :

and if :

The galactic extinction is higher than the one predicted by RC2 formula
for low galactic latitude (). The adopted galactic
extinction is *ag*=*ag*(*BH*)+0.20, where *ag*(*BH*) is calculated from Rel. 1 and
Rel. 2.

Supergalactic coordinates *sgl*, *sgb* are calculated (in degrees to )
from *l*2, *b*2 using the coordinates of the supergalactic pole
*l*2(pole) = 47.37 deg *b*2(pole) = 6.32 deg and the coordinates of the origin
*l*2(origin) = 137.37 deg; *b*2(origin) = 0 deg according to
de Vaucouleurs et al. (1976).

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