VRI photometry of stars in the fields of 12 BL Lacertae objects

Cattedra di Astrofisica, Università di Perugia, Via A. Pascoli, I-06100 Perugia, Italy

Corresponding author: Send offprint request to: G. Tosti; tosti@astrpg.pg.infn.it

Received: 25 July 1995
Accepted: 8 September 1995

Abstract

We present VR_c I_c Johnson-Cousins magnitudes of field comparison stars for twelve BL Lacertae objects belonging to the largest sample of blazars which is monitored at the Perugia University Observatory. The sequences reported here can be used in the long–term CCD photometric monitoring of BL Lac objects aimed to understand the characteristics of their variability. Finding charts for all of these comparison sequences are also included in this paper.