Extension of Tycho catalog for low-extinction windows in the galactic bulge

We present in this work secondary catalogs(1) up to m(Val) similar to 13 ba sed on the Tycho reference frame (ESA, 1997) for 12 selected low-extinction fields towards the galactic bulge. The observations have been performed wi th the Askania-Zeiss Meridian Circle equiped with a CCD camera, located at the Abrahao de Moraes Observatory (Valinhos, Brazil) and operated by the In stitute of Astronomy and Geophysics, Sao Paulo University. The presented ca talog, though not complete, has been designed to help in intensive search p rogrammes (e.g. microlensing and variable searches) and therefore the selec ted standards have a high astrometric and photometric (V band, approximatel y) quality. The mean precisions obtained were 0.0018(s) in alpha, 0.013 " i n delta, 0.030 for the standard deviation in magnitude and 0.0042 for the m agnitude when weighted with the error bars in each night (in the mean, 42 s tars for the catalog of each window).