A photometric study of the bright cloud B in Sagittarius. VI.1592 new variable stars and 30 diffuse objects.

1592 new variable stars and 30 diffuse objects have been detected on B, V and R plates obtained at the Schmidt telescopes of Mount Palomar Observatory (1968) and the European Southern Observatory (1976-1983). After detection, photometry (Observatoire de Lyon) and astrometric measurement (ESO/Garching) of these objects, we have determined the parameters R.A., D, l, b, R[Max], R[Min], A. We have established that: 1) Among the 30 diffuse objects: 4 appear in the form of a nebulosity; 1 is a star surrounded by a nebulosity; 4 are suspected of being planetary nebulae; 21 others seem to be galaxies or galaxy nuclei belonging in all probability to the Ophiuchus cluster. 2) Among the 1592 variable stars: 1 is an IR variable (No. 1593); 332 are observable only on R plates; 1221 are found on B and V plates; 296 have an observed amplitude together between 2.1 and 3.0 m_R_ (histogram δm/N); the number of variable stars decreases rapidly towards the high amplitudes; the surface density of variable stars per square degree in this direction towards the centre of the Galaxy increases from 1.05 to 31 in the two explored fields, each of which covers an area of 5.5^deg^ x 5.5^deg^. 3) Star No. 856 is a proper motion star.