We have calibrated the effective temperatures of the low main sequence stars ranging spectral types from F0 to K5 versus [Fe/H] and colours (B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and ubvy-β, using a large sample of dwarfs and subdwarfs. The effective temperatures, scaled to direct T_eff_ determinations via reliable angular diameter

The 3CRR sample of radio galaxies and quasars has been cross-correlated with the ROSAT PSPC All-Sky Survey. About 25 per cent of the objects have been detected in the 0.2-2.4 keV range, the large majority being powerful radio and X-ray emitters with a range of X-ray luminosities between 10^44 and 10^46 erg s^-1. The 0.2-2.4 keV spectrum of the

We present a procedure for obtaining the cluster densities in terms of the probability, P_n_(r), for a randomly placed sphere of radius r to contain n galaxies and the cluster density profiles. We then discuss a method for computing P_n_(r) and use it to obtain the density of Abell clusters in cold dark matter models with different biasing.

Photometric observations of 1620 Geographos in 1993 and 1994 are presented and, in combination with previously published data, are used to derive models of Geographos. We estimate that the sidereal period of rotation is 0.21763860 +/- 0.00000003 days (5^h13^m23.975^s +/- 0.003^s). The sense of rotation is retrograde. The ecliptic coordinates of the

This is the first paper of a series aimed at studying the structural and photometric properties in the optical band of a sample of 95 radio galaxies. Detailed surface photometry in the B and R bands is reported here for 29 objects. We give contour plots and complete structural (ellipticity, position angle, Fourier coefficients) and photometric

During our recent observing run at La Silla (April 26-28, 1996), we had the chance to experiment successfully a previously unexplored capability of the NTT: high-dispersion spectroscopy using the full slit length of EMMI.