This investigation is based on Hα observations of high spatial resolution. They stem from an enhanced network region near disk centre of the sun and consist of broad-band and narrow-band images taken with the two-dimensional ``Göttingen'' Fabry-Perot spectrometer mounted in the Vacuum Tower Telescope at the Observatorio del Teide/Tenerife. The `

We correlate an overlapping period of earthshine measurements of Earth's reflectance (from 1999 through mid-2001) with satellite observations of global cloud properties to construct from the latter a proxy measure of Earth's global shortwave reflectance. This proxy shows a steady decrease in Earth's reflectance from 1984 to 2000, with a strong

We report the first results of a Cycle 12 Hubble Space Telescope SNAP program imaging the C III] 1909Å lines in planetary nebulae (PNe) and extragalactic H II regions using WFPC2 with the F185W filter. To date(2004 March), four PNe (NGC 6210, NGC 6720, NGC 6826 & NGC 7662) and three H II regions (LMC N160A, SMC N81 & NGC 2363) have been observed

Two independent sets of Chandra and HST images of the nuclear region of M31 allow registration of X-ray and optical images to ˜ 0.1''. This registration shows that none of the bright ˜ 1037erg s-1 X-ray sources near the nucleus is actually coincident with the central super-massive black hole, M31*. A 50ks Chandra HRC image shows ˜ 2.5σ evidence for

We explored the regions within a radius of 25 arcsec around 473 nearby, low-metallicity G- to M-type stars using (VR)I optical filters and small-aperture telescopes. About 10% of the sample was searched up to angular separations of 90 arcsec. We applied photometric and astrometric techniques to detect true physical companions to the targets. The

This paper presents some formulae to calculate moments of inertia for solids of revolution and for solids generated by contour plots. For this, the symmetry properties and the generating functions of the figures are utilized. The combined use of generating functions and symmetry properties greatly simplifies many practical calculations. In addition