We present the results of the spectral analysis of 11 OB stars in Cyg OB2, among them seven giants and supergiants. The projected rotational velocities of these stars are low or moderate. We find that only one of the stars (previously classified as luminosity class V) shows helium enhancement, and that this turns out to be compatible with standard

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A study of [Fe Ii] lines at various positions within the H Ii regions M42 and M43 is presented. The relative intensities of selected optical [Fe Ii] lines are shown to be correlated with the intensity of the apparent nebular continuous spectrum. Since the continuum of H Ii regions is known to be mostly stellar radiation scattered by dust intermixed

Highly collimated bipolar outflows have been detected in the planetary nebula NGC 6572 via ground-based optical imagery and high-resolution long-slit spectroscopy. Kinematics and morphology together provide strong evidence of a direct interaction between the collimated outflows and the nebular elliptical shell, creating a double point-symmetric

Regular monitoring of the light curves of blazars has become increasingly valuable as space missions such as ROSAT, CGRO and ASCA have subjected many objects to detailed multi-wavelength monitoring. Over recent years collaborations such as the OJ-94 collaboration have benefitted greatly from the input of amateur astronomers observing both visually

We present a CCD-based photometric survey covering 870 arcmin^2 in a young stellar cluster around the young multiple star sigma Orionis. Our survey-limiting R, I, and Z magnitudes are 23.2, 21.8, and 21.0, respectively, the completeness being about 2.2 mag brighter. From our color-magnitude diagrams, we have selected 49 faint objects (I=15-21 mag)