... This calibration approach is recommended when dealing with high frequency data from the old ATCA correlator, especially at 3mm wavelengths. ... The approach described here exploits the dual frequency bands that were available with the old correlator. ... Rather the current approach assumes that you have a single Miriad dataset containing bandpass calibrator, phase calibrator, flux density calibrator and program source. ... MFCAL . ... Input multi-source, dual-band dataset. select=source(1921-293) . ...

... The upward propagating HF wave is reflected at a particular height. ... The instabilities seen by the radar shortly after the HF is turned on can be divided into two types according to the degree of sophistication required in the model describing the response to the E field of the HF wave. ... The first kind occurs at a particular height determined by k vector and frequency matching conditions on the HF wave, the low and high frequency plasma waves, and the radar EM wave. ... Incoherent Scatter . ...

Top] [Prev] [Next] [Bottom] . In This Chapter.. ... Calculating NICMOS Imaging Sensitivities / 92 . WWW Access to Imaging Tools / 97 . Examples / 97 . ... Next, we describe how to determine the system sensitivity. We then describe the ways in which you can determine the exposure time required for a given observation and the signal to noise that will be achieved; examples are provided. ... We also describe how to calculate signal to noise ratios and exposure times by hand for NICMOS. ...

... The most precisely determined characteristic for accreting neutron stars (NS's) is their period. ... Period changes show fluctuations. ... Some applications of stochastic processes in astrophysics especially in accreting systems were discussed in Lipunov (1987),Hoshino Takeshima (1993) and Lipunov (1992).In Hoshino Takeshima (1993) the authors, using simple models of MHD turbulence, try to explain aperiodic changes in X-ray luminosity of X-ray pulsars. ... Here, -constant angular momentum. ...

Some radio clocks and related timekeeping gear have a pulse-per- second (PPS) signal that can be used to discipline the local clock oscillator to a high degree of precision, typically to the order less than 50 us in time and 0.1 PPM in frequency. ... Either way requires conversion of the PPS signal, usually at TTL levels, to RS232 levels, which can be done using a circuit such as described in the Gadget Box PPS Level Converter and CHU Modem page. ...

Next: Generation from Ground Calibration Up: PIXTOPIXSENS Previous: PIXTOPIXSENS Contents . ... The PixToPixSens file describes the inverse detector sensitivity normalized to the average sensitivity. ... PixToPixSens consists of two image extension. ... The keyword CFRR specifies the average count rate (units: count/CCD frame) in the flatfield exposures used to generate the image extension. The image extension LEDTEMPLATE holds the description of the LED illumination pattern. ... n.a. 2 . ...

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... 50 Weirdest Objects . ... Observing springtime deep-sky objects with a large telescope . ... What is the baseline for determining the magnitude scale of celestial objects? Why do brighter objects have negative numbers? ... He called the brightest 1st magnitude and the faintest 6th magnitude. ... Also, to assign a magnitude to the brightest planets, the Moon, and especially the Sun, scientists would have to work with negative numbers. Get instant access to subscriber content on Astronomy.com! ...

Next: The /dev directory Up: The root filesystem Previous: The root filesystem . The /etc љ directory contains a lot of files. ... See the chapter on init љ for further information. /etc/passwd љ . ... Lists the filesystems mounted automatically at startup by the mount -a command (in /etc/rc љ or equivalent startup file). ... etc/issue љ . ... See the magic љ and file љ manual pages for more information. /etc/motd љ . ... Files executed at login or startup time by the Bourne or C shells. ...

... The Average Color of the Universe . ... This whimsical question came up when trying to determine what stars are commonplace in nearby galaxies. ... Also cataloged as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. ... About 50 million light-years distant in the northern constellation Pegasus, NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. ...

... Keywords: Proper Motions, Schmidt Plates, Astrometry, Guide Star Catalog, Palomar Sky Survey . In this paper we describe a program of determining proper motions from digitized scans of 1950's-era Palomar Sky Survey (POSS) Schmidt Plates and 1980's-era Palomar Oschin Schmidt `Quick V' plates that were taken for the Hubble Space Telescope ( HST ) Guide Star Catalogue. ... Arrows indicate the magnitude and direction of the proper motion for the stars. ...