... Colours of stars and galaxies hold information on intrinsic and extrinsic parameters, such as stellar temperatures and galaxy populations, selective absorption and colour changes due different dust contents and inclination angles of galaxies, as well as galaxy redshifts and evolution. ... The colour magnitude diagram of 65000 galaxies to which all above-mentioned quantities and others contribute can only be explained by comparison with simulations. ... Colours are also of technical help. ...

... We performed photometry on both the original and deconvolved images of NGC 6352. ... Aperture photometry was performed on all stars identified in the deconvolved master frames with aperture radii of 4 and 5 pixels for the F555W and F785LP images respectively. ... Fig. 2 indicates that the scatter about the mean faint star sequence is much smaller for the aperture photometry of the deconvolved images than for the PSF fits to the original images. ...

Once students get the hang of it, they can find and measure the brightness of Delta Cephei in a few minutes. ... of Delta Cephei . ... Oct. ... The following table lists the measurements of Delta Cephei made by one amateur astronomer in autumn 1990. ... 4.0 . ... This activity is a simplified version of one that appeared in Hands-On Astrophysics, a series of activities prepared by the American Association of Variable Star Observers with support from the National Science Foundation. << previous page | ...

... Analysis of in-orbit data closely follow the CSL data analysis. Stars with known astrometric positions are matched with their image centroids. ... The measured position, the expected position and the offset between the measured and expected positions are calculated and written into a file. ... select catalogued positions for different observations/pointings (e.g. positions of objects in photometric sequence) . ... The new distortion map was generated from in-flight observations of the G153 field. ...

Stellar Clusters are very useful laboratories for empirically studying stellar evolution. ... All cluster stars are at the same distance . All cluster stars have the same physical age . ... CM diagram Young Cluster In this case we see the Main Sequence fully represented. The blue dots represent massive stars with short main sequence lifetimes. ... Thus, identifying the most massive star which is still on the main sequence is an effective means of determining the age of a stellar cluster. ...

... July 13, 1996 . M81: A Bulging Spiral Galaxy . ... Explanation: Few stars are still forming in the old giant spiral galaxy M81. The blue regions in this picture - representing ultraviolet light - highlight regions of bright young stars and star formation and appear rare than in M74 and M33 . ... M81 is therefore classified as spiral galaxy type "Sab" on the Hubble Sequence of Galaxies . ... A massive density wave circulates around the center of spiral galaxies. ... About APOD | ...

... It provides long range planning information to the scheduling team; it provides bright object, timing, and orientation information to the observation planning team; and it provides graphical description of the observations and their constraints. ... The GUI graphically displays the constraints that are computed by Spike and stored in the description files and in the database. ... BOAS processes all bright objects that have entered the database since the last time BOAS was run. ...

... The double star 54 Leonis, spiral galaxy NGC 3198, and emission nebula NGC 3199 . ... Globular cluster NGC 2808, elliptical galaxy NGC 2986, and the Sextans Dwarf . ... Generations of stars in a globular . Hubble finds three generations of stars formed early in globular cluster NGC 2808's life, instead of a single "baby boom." ... The analysis of Hubble data from the massive globular cluster NGC 2808 provides evidence that star birth occurred over three generations early in the cluster's life. ...

... A comparison of the computed and experimental relations F max ( H), as well as comparison of drift scans of point sources across different horizontal cross-sections of the BP with the corresponding computed cross-sections were made. ... The drift scans of the point source 3С84 (H=87 o ) at the wavelength 7.6 cm across the horizontal cross-sections of the BP (black lines) and the computed horizontal cross-sections of the BP corresponding to them (red lines). ...

Nova in M31 2000 3 . ... From Giovanni Sostero (Remanzacco Observatory): at the end we have found a good Nova candidate in the course of our monitoring program in M31. ... Remanzacco Observatory Light curve This is a preliminary lightcurve of Nova M31-3 from the images we collected and those provided by others. ... vsnet-alert 5346 ] [FWD] Suspected Nova in M 31 . ... vsnet-alert 5349 ] (fwd) M31 possible nova . ... vsnet-alert 5355 ] [FWD] New image of the possible Nova in M31 (GSo) . ...

We present quasi-simultaneous multi-colour optical/near-IR photometry for 157 radio selected quasars, forming an unbiassed sub-sample of the Parkes Flat-Spectrum Sample. ... The spectral energy distributions of the radio- and optically-selected sources are quite different. ... We show that the colours of our red quasars lie close to the stellar locus in the optical: they will be hard to identify in surveys such as the Sloan Digital Sky Survey. ...