... One Jansky (Jy) is defined as 10 -26 Wm -2 Hz -1 , so it is a unit of measurement of the spectral flux density, F . ... 3x10 -12 . ... erg sec -1 cm -2 ?m -1 . ... where m is the magnitude and F o the zero-point flux for the given photometric band. ... Surface brightnesses are generally measured in Janskys arcsec -2 , MJy steradian -1 or magnitudes arcsec -2 . If you have a surface brightness S in MJy steradian -1 , then you can use: S [Jy arcsec -2 ] = S [MJy ster -1 ] x 0.084616. ...

... It lists the coefficients defining the colour transformations, the zero points for the different filters and the aperture radii used in the photometric calibration analysis. ... The AB system zero point of the filter FilterID is stored in the keyword ABM0 FilterID , e.g. the AB zero point of the the U-filter is stored in ABM0U. The flux conversion factor derived from White Dwarfs of the filter FilterID is stored in the keyword FCF FilterID . ... description . ... AB Flux conversion factor of U . ...

... An OBJECT column gives the name of the object observed (usually a star name). ... In critical cases, it is common practice to measure sky on two or more positions around a target object, and these positions must be identified. ... A general treatment of this problem requires a column called OBJECT, bearing the usual name of the object (as in the star tables); a column labelled STARSKY, to distinguish between star+sky, star alone, or sky alone; and additional columns to identify the sky position. ...

... Virtually all detectors and telesco pes are sensitive to only a particular range of frequencies or wavelengths. ... Flux per unit wavelength or frequency So in practice, when we measure how much radiation we receive from some object, we usually mean the energy at some particular frequency, not the integral of the energy over all frequencies (which would be the bolometric brightness). ... But imaging data at UV, optical and IR wavelengths often uses a different approach: broad-band imaging. ...

Two major reasons: the number of stars isn't really seven (it's many more), and they all have different brightnesses, so that you see more or fewer of them depending on viewing conditions. The brightness of stars is measured on the magnitude scale, where the most prominent stars in the sky are around 1st magnitude, and the faintest you can see with your eye are about 6th. ... I think this makes it quite likely that the list will be truncated at Taygeta, giving six visible stars. ...

... SEARCH ASP SITE: Match ALL words Match ANY word . ... ASP Conference Series . ... Accidental Astrophysics: The Devil's In the Magnitudes, Part II . ... The star second to the Sun in brilliance is Sirius. ... Recall the magnitude system, passed down to us through a hundred generations of sky watchers, as a means of quantifying stellar brightness ("Accidental Astrophysics," May/June, p. 9). ... Yes, it is a magnitude difference, but that difference is due to the distance between us and the star. ...

... Meade Instruments Corporation . ... Choosing the Right Microscope . ... On most microscopes the specimen glass remains fixed while the microscope's objective lens and eyepiece move as a unit up or down to focus the image. ... Eyepieces of varying powers work with objective lenses of varying powers to yield a range of microscope magnifications. ... Magnification: The effective magnification of a microscope is determined by multiplying the eyepiece power by the objective lens power . ... about meade |...

Each point in this graph represents one star in NGC 2808. The vertical axis represents the brightness (as measured through Hubble's near-infrared F814W filter) of the stars (the brightest stars near the top). The horizontal axis represents the colours of the stars, with bluer stars to the left and redder to the right (blue magnitude minus near-infrared magnitude). ...

Distributed Software for Observations in Near Infrared V. Gavryusev 1 and C. Baffa Osservatorio Astrofisico di Arcetri E. Giani Dipartamento di Astronomia, Universit`a di Firenze Abstract. ... The processes denoted for control of hardware (telescope and other instruments) should be executed currently on PC dedicated for this task under DESQview/X, while all other components (user interface, tools for the data analysis, etc.) can work also under Unix. ... 1993, Di Giacomo et al. 1993). ...

... 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 ( )...

Measurement of Sky Brightness at the Iranian National Observatory Davoud Afshari1 and Sadollah Nasiri1,2 1Physics Department, Zanjan University, Zanjan 45195-313, Iran; Institute for Advanced studies in Basic Science (IASBS), Zanjan 45195-1159, Iran; Measurement of light pollution 2 Introduction Among 34 candidate sites at the central part of the country, 5 sites namely Garkesh (in Kashan ), Kolahbarfi(in Kashan ), Deynava (in ... One of these is light pollution. ...

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. ...

... September 2, 1997 . Dark Sky, Bright Sun . Credit: STS-82 Crew , NASA . Explanation: In low Earth orbit there is not enough atmosphere to diffuse and scatter sunlight, so shadows are black and the sky is dark - even when the Sun shines. The harsh lighting produced this dramatic effect as mission specialist Gregory Harbaugh photographed colleague Joseph Tanner during their second spacewalk to service the Hubble Space Telescope in February 1997. ... About APOD > . ...

Astronomy Picture of the Day . ... Credit: E. Karkoschka ( University of Arizona ), HST , NASA Explanation: This delightfully detailed false-color image of Saturn was taken in January 1998 by the orbiting Hubble Space Telescope. The picture is a combination of three images from Hubble's NICMOS instrument and shows the lovely ringed planet in reflected infrared sunlight . ... 2007 . ... Publications with keywords: Saturn - rings - infrared . Publications with words: Saturn - rings - infrared . ...

Monte Carlo Methods for Including Calibration Uncertainties in Model Fitting Analyses Jeremy J. Drakea , Peter Ratzlaffa , Vinay Kashyapa , Richard Edgara , Rima Izemb , Diab Jeriusa , Herman ... University, Cambridge, MA 02138 MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 b c SUMMARY · Instrument response uncertainties almost universally ignored in astrophysical X-ray ... Limiting accuracy of Chandra ACIS reached in spectra with 10 4 counts. ...

... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . ... Circular polarization of the bright side of Iapetus versus wavelength, obtained with FORS2 at the ESO VLT during the night 2011-03-28 at a phase angle of 0.77 . ... It can be noted that a change in signal occurs in circular polarization observations that are taken after rotating the instrument by 90 degree with respect to the intial position angle on the sky. ...

... 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). ...

To main of Laboratory . The research work and design of optical and optical-electronic devices are carries out by laboratory staff: . ... Lens: . ... In the layout 1 prism systems perform functions of dispersive element, corrector of aberrations, optical reducer. ... Spectral range 200 - 400 nm; . ... Back Forward . ... The main corrector's function are compensation of field aberrations of the main spherical mirror of a telescope (diameter of 600 mm, f'=1200 mm) and increase aperture ratio. ...

Q: Are the magnitudes in the ETCs AB or Vega magnitudes? ... Q: How is the signal to noise defined? A: In optical and infrared imaging, the applications display a signal to noise over the PSF area, which is computed in a circle of radius seeing/plate_scale. ... In optical imaging only, a second signal to noise is computed which is the signal to noise at the central pixel. ... A: The template spectra stored in the database are measured or simulated spectra covering different wavelength range. ...

... AstroCC is a coordinate conversion utility for astronomy. It accepts an object designation or the coordinates of an object and calculates coordinates in alternative systems, and at different dates, times, and locations. It also provides lunar and bright planet coordinates to aid in planning observations. ... BJD values may also be retrieved from http://astroutils.astronomy.ohio-state.edu/time/utc2bjd.html which is based on Eastman et al. ... Coordinate data are obtained from SIMBAD. ...