There are no alterations with respect to Paper VII. The mean error was or in the sky.
Gradation curve and absolute calibration:
With the U and V passbands well inside the domain of sensitivity of the respective emulsions, no problems were encountered during reduction, which followed closely the procedures laid down in Paper VII. In the red spectral region, however, the long wavelength cut-off of the passband coincided with that of the 103-aF emulsion. At the limiting wavelengths of their sensitivity, emulsions tend to steepen up their gradation curves. So special care had to be taken to establish the true run of these curves.
While in the visual spectral region the effect of airglow is very much like that in the B-band (Paper VII), in the red and ultraviolet spectral region the airglow affects the Milky Way much more. This is due to the higher emission in the red, and/or to the lower surface brightness of the Milky Way in the U-band. Columns 3-5 of Table 2 (click here) give the airglow values for all plates. As defined in Paper VII (Eqs. (8) and (9)), IA0 is the zenith brightness in S10 units, while C2 is connected directly to the mean altitude of the airglow layer and determines its variation with respect to zenith distance z.
The corrections were made using the data published by Levasseur-Regourd & Dumont (1980). The transformations into the respective passbands were done by multiplying these data with the appropriate solar intensity ratio.
Elimination of foreground stars and averaging of
The procedures of elimination and averaging were the same as in Paper VII. When the photometries were combined to U-B, B-V, V-R maps (B from Paper VII), a few small areas of "astrophysically impossible" colours showed up, which are thought to result from inadequately eliminated stars or star clusters. In Table 3 (click here) data obtained from a composite picture of Hovest (1995) contains the positions of the areas (Fig. 5 (click here)), where our photometries have to be treated with caution.
|IC 2602 in Carina||B*), V|
Errors and comparisons with other photometries:
As in Paper VII, the three photometries are compared to others available. In Table 4 (click here) the relations are presented. The comparison for the B band photometry is taken from Paper VII. Except for the early work of Elsässer & Haug (1960) all relations stay within in scale. It seems probable, however, that our scale is correct within .
All values in S10 units;
photometries: C (Classen 1976), D (Dachs 1970), EH (Elsässer & Haug 1960), H (Hoffmann et al. 1990, 1993), M (Mattila 1973), LR (Leinert & Richter 1981), P (Pröll et al. 1980), PM (Pfleiderer & Mayer 1971), S (Seidensticker et al. 1982), T (Tappert et al. 1993), To (Toller 1989).