... The J, H and K bands are characterized by a bright background, such a background is mainly due to the emission of atmospheric lines and of thermal radiation. ... If the source cover a large fraction of the slit, spectra off-source must be observed to adequately sample the sky background. ... The on chip integration time (time spent in each position of the slit) must not exceed 40 seconds in J and H bands and 60 seconds in K band. ... We suggest a sequence of 10 for each elementary integration time. ...

... A set of formulae has been developed to correct aperture photometry for CTE loss with dependencies on the X and Y positions, the background counts, the brightness of the star, and the time of the observation. The observations indicate that for very faint stars on a very faint background, the CTE loss from the top to the bottom of a chip has increased from about 3% shortly after the cool-down of WFPC2 (April 23, 1994) to roughly 40% in February 1999. ... Figure 5: Same as Figure 4 for X-CTE. ...

... All primary data reduction was done with MIDAS. The frames were corrected for bias, dark, and flat field in the same way as for reduction of the 2D frames of NOT long-slit spectra. ... The SB profiles were decomposed into two components: one with a gaussian distribution in the central part and the second being an exponential disc. ... The final photometric errors take into account the instrumental errors and the error of transformation to the standard photometrical system. ...

In this gallery are many images of Low Surface Brightness Galaxies which have recently been discovered and analyzed. ... The central surface brightness of this galaxy is 24.28 . Malin 2 This galaxy is another huge disk galaxy with a scale length of 15 kpc and a redshift of 15000 km/a. The high surface brightness knot in one of its spiral arms actually has the same color, luminosity and H-alpha equivalent width as the entire Large Magellanic Cloud . ... Truly it is a Low Surface Brightness Galaxy. ...

... Using a simple 2-D Gaussian Point Spread Function (PSF) on a constant (flat) sky background, I derive a theoretical photometric and astrometric performance model for analytical and digital PSF-fitting stellar photometry. ... The photometric performance is maximized when either the effective background area or the effective-background-level measurement error is minimized. ... An important, but frequently ignored, noise source is the uncertainty of the measurement of the effective background level ( )...

... Flux density at 1 GHz (/Jy): 19 . ... Notes: This is the remnant of the SN of AD 1006. ... Optical: Filaments to the NW, with broad H component. ... Point sources: The background Schweizer Middleditch star is near the middle of the remnant. ... van den Bergh 1976, ApJ, 208, L17. Optical observations. ADS . ... X-ray spectroscopy. ... Schweizer & Middleditch 1980, ApJ, 241, 1039. ... Optical spectroscopy of the Schweizer Middleditch star. ... Optical spectroscopy. ... 2013, A&A, 552, A9. ...

... In the three intervening decades there have been many observations of this diffuse emission over a wide range of x-ray energies. ... During the 1970's researchers at the University of Wisconsin, lead by Dr. William Kraushaar, used a series of sounding rocket flights to map the diffuse x-ray emission from the sky in several bands. ... University of Wisconsin Sky Survey map of the B-band (0.13-0.188 keV) x-ray intensity. ... University of Wisconsin Sky Survey map of the 2-6 keV band x-ray intensity. ...

... Copyrightї1997 Bob Yen (byen@ix.netcom.com) (http://www.comet-track.com/hb/hb.html) . ... Information on Comet Hale-Bopp for the Non-Astronomer Hale-Bopp rotates about twice a day (3/14/97) . ... The Comet Observation Home Page was been selected to receive the Griffith Observatory Star Award for the week of February 2 - 8, 1997 for excellence in promoting astronomy to the public through the World Wide Web. ... Typically, about 1,000 individual users/computers access this page every day. ...

Next: Gravitational Wave Background from Previous: Galactic Gravitational Wave Background . ... It is intuitively clear that at frequencies above the critical ones for our Galaxy, one will detect rare bright jerks produced by coalescing white dwarfs   (at a rate of 1 per 100 year) and NS (at a rate of 1 per - year) in our Galaxy, against a background of the extragalactic stochastic GW. ... Firstly we consider GWB from close individual galaxies, and then will discuss overall extragalactic GWB. ...

The night sky brightness, together with number of clear nights, seeing, transparency, photometric stability and humidity, are some of the most important parameters that qualify a site for front-line ground--based astronomy. ... Night sky at ESO-Paranal (Chile). ... Night sky brightness data . ... UBVRI night sky brightness at ESO-Paranal during sunspot maximum (A 2003, PDF) . ... The Dancing Sky: six years of night sky observations at Cerro Paranal (Starlight 2007 conference proceedings, PDF) . ...