BVRI photometry for stars in the field of BL Lacertae (literature summary) The table below shows positions and BVRI photometry for stars in the field of the variable galaxy BL Lacertae drawn from nine sources in the literature. My concern about there being possibly discrepant sources was that recent visual observations showed considerable scatter even in observations made a few minutes apart by different observers. While the galaxy is known to exhibit large variations on timescales of weeks, the shorter-term variations are much smaller (0.1-0.3 at most on nightly timescales). The AAVSO and AFOEV visual charts are clearly based on the photoelectric observations of Bertaud et al. (1969, 1973; see references below). Gary Poyner has just written to say the BAA chart is based on the same sequence. Comparison of these data against newer observations (not necessarily better!) suggest the V magnitudes for the stars are correct within perhaps +/- 0.05 mag. The only serious discrepancy involves star 'b', which is the one immediately east of the galaxy. DuPuy et al. (1969) show that this star is a mid-K giant; given the scatter in the published results, it is possible that the star is slightly variable. This star is fairly red, so probably should be avoided by visual observers in any case. The two sources of VRI photometry (both on the Cousins system) seem to be discrepant until one looks at the stated errors on the measurements, which in both cases are fairly soft, in the +/- 0.05 to 0.10 range. Thus the data are consistent, if somewhat uncertain. The table shows star names based on the Bertaud scheme as shown on the charts in their two papers. N.B. that more recently the lower case lettered stars b,c,h,k near the galaxy have tended to be referred to by capital letters. Compare the star positions before amending your charts! The positions come either from the GSC v1.1 (source G) or the USNO A1.0 (source A) catalogue for the fainter stars. For a few additional bright stars in the field, I have added information from the Hipparcos/Tycho database (source T). The position for BL Lac itself comes from the NED database. GSC names for the brighter stars are listed in the notes along with a few other comments. The BVRI photometry is given as available in no particular order, with the sources listed at the end of each line. The stars are arranged in order of decreasing brightness. Finally, the AAVSO on-line chart can be downloaded from: http://www.aavso.org/charts.html Also, note that the Guide Star Photometric Catalogue sequence P236 is located within about 20' southeast of the galaxy. \Brian +++++++++++++++++++++++++++++++++++++++++++++++++++++ BVRI photometry for stars in the field of BL Lacertae Name RA (2000) Dec s V B-V V-R R-I source BL Lac 22 02 43.3 +42 16 40 ~1.0 HD 209438 22 02 25.4 +42 25 32 T 8.41 1.03 Tycho HIP 108776 22 02 05.7 +42 22 47 T 10.92 Tycho G3206-1959 22 02 45.5 +42 19 11 T 11.6 0.3 Tycho BL Lac alf 22 02 54.0 +42 13 19 G 12.02 0.45 M72 BL Lac b 22 02 45.4 +42 16 35 G 12.78 1.74 0.85 0.84 S85 12.90 0.91 0.87 F96 13.06 1.66 M72 13.04 1.64 R70 1.66 D69 12.90 1.78 B69 12.89 1.67 B73 12.89 1.66 K70 BL Lac e 22 02 16.7 +42 16 50 G 12.99 0.69 B69 BL Lac A 22 02 23.8 +42 17 17 G 13.31 0.74 B73 BL Lac f 22 02 53.6 +42 17 48 G 13.26 1.05 B69 13.36 1.04 B73 13.34 1.02 K70 BL Lac a 22 02 30.8 +42 17 10 G 13.43 0.60 B69 13.39 0.61 B73 13.39 0.57 K70 BL Lac B 22 02 39.6 +42 13 38 G 13.72 0.97 B73 13.72 0.94 K70 BL Lac g 22 02 35.1 +42 18 49 A 14.10 0.96 B69 BL Lac c 22 02 40.1 +42 17 10 A 14.19 0.90 0.50 0.46 S85 14.26 0.47 0.47 F96 14.28 0.92 B69 14.26 0.93 B73 14.23 0.88 K70 BL Lac h 22 02 32.7 +42 16 47 A 14.31 1.37 0.71 0.67 S85 14.40 0.67 0.66 F96 14.42 1.39 B69 BL Lac C 22 02 33.4 +42 14 25 A 14.50 1.06 B73 14.41 1.02 K70 BL Lac N 22 02 48.3 +42 18 46 A 14.65 0.85 B73 14.63 0.80 K70 BL Lac O 22 02 30.6 +42 19 00 A 15.29 1.02 B73 15.28 1.01 K70 BL Lac k 22 02 36.0 +42 16 54 A 15.44 0.82 0.56 0.54 S85 15.47 0.47 0.46 F96 15.48 0.88 B69 BL Lac 9 22 02 46.4 +42 16 56 A 15.79 1.08 M77 Notes: HD 209438 spec type K0. HIP 108776 V-I = 0.89, uncertain variable; IRAS 22000+4208. BL Lac alf GSC 3206-1639. BL Lac b GSC 3206-1047; spec type k3/4iii. BL Lac e GSC 3206-0727. BL Lac A GSC 3206-0931. BL Lac f GSC 3206-0873. BL Lac a GSC 3206-0907. BL Lac B GSC 3206-0613. Sources: B69 Bertaud et al. 1969, A&A 3, 436. B73 Bertaud et al. 1973, A&A 24, 357. D69 DuPuy et al. 1969, ApJ 156, L135. F96 Fiorucci & Tosti 1996, A&AS 116, 403. K70 Kinman, priv. comm. cited in B73. M72 Milone 1972, PASP 84, 723. M77 McGimsey & Miller 1977, AJ 82, 453. R70 Racine 1970, ApJ 159, L99. S85 Smith et al. 1985, AJ 90, 1184.