Stars brightness

Sodium Guide Star Brightness. From the properties of the Na atom and the Na layer (Table 1), we can estimate the power needed for the AO system. Assuming isotropic emission and no saturation, the photon flux F of the LGS observed with the WFS is given by ... 

One of the main limitations of conventional AO is anisoplanatism most objects of scientific interest are too faint to act as their own reference source for AO correction, and it would be useful to use bright nearby objects, preferably stars, which act as point sources. However, the light from the object of interest which is intercepted by the telescope passes through a part of the turbulence which is different from that traversed by the light from the reference star. This leads to a decorrelation between the wavefront measurements obtained with the reference star and that which should be applied to correct the wavefronts... 

The development of adaptive optic (AO) systems to correct for wavefront distortions introduced by the atmosphere represents one of the major advances in astronomical telescope technology of the 20th century. However, in spite of the great progress in AO, sky coverage is limited to sources located near bright stars that provide a measure of wavefront distortions. 

In order to overcome the requirement of having a bright "natural guide star" (NGS) near an astronomical source, a first generation of laser guide stars (LGS), or laser beacons, has been deployed to produce bright artificial stars from which wavefront distortions can be assessed. LGSs consist of the... 

Since a heterodyne receiver is an amplitude and phase detector, it could nicely be used to correlate optical signals received at various remote sites. The local oscillator can be a single laser distributed by optical fiber to the various sites or local lasers that can be synchronized "a posteriori" by reference to a common source (e.g. a bright star). 

Wiener inverse-filter however yields, possibly, unphysical solution with negative values and ripples around sharp features (e.g. bright stars) as can be seen in Fig. 3b. Another drawback of Wiener inverse-filter is that spectral densities of noise and signal are usually unknown and must be guessed from the data. For instance, for white noise and assuming that the spectral density of object brightness distribution follows a simple parametric law, e.g. a power law, then ... 

Looks like you ll be busy for a while, I say, as the couple pay for a ram s head pendant for him and a lightning-bolt brooch for her, and their place is taken by a round-eyed girl still clutching the consent form for ear-piercing and fingering her own bright pink lobes with awe. She starts to inspect the stars. 

Prophetical passages concerning the present times, in which the person, character, mission, c. c. of Richard Brothers, is clearly pointed at as the Elijah of the present day, the bright star to guide the Hebrews, c. selected from the writings of Jacob Behmen. .. London Printed for G. Riebau, No. 439, Strand, 1795. v.p. 

To the three bright stars of my universe Nancy, Lindsey, and Amanda... 

The 27-cm telescope is equipped with four CCD detectors and measures the light curves of bright stars in the wavelength range 370-950 nm. The scientific goals of the mission are ... 

The Hubble mid-UV echelle spectra extend blueward to 2130 A for hot stars, or to 2380 A or 2885 A for cooler ones. Redward they extend to 3120 A for faint stars, to 2885 A for bright hot stars, and to 3150 A for bright cool stars. These spectra are flux-calibrated, which fixes the mid-UV continuum normalization. 

Scl is a close companion of the Milky Way, at a distance of 72 5 kpc [7], with a low total (dynamical) mass, (1.4 0.6) x 107Mq [8], and modest luminosity, My = —10.7 0.5, and central surface brightness, Soy = 23.5 0.5 mag/arcsec2 [9] with no HI gas [10]. CMD analysis, including the oldest Main Sequence turnoffs, has determined that this galaxy is predominantly old and that the entire star formation history can have lasted only a few Gyr [11]. 

Photometry and Spectroscopy of Bright Stars in the Carina dSph Galaxy... 

Abstract. We present the results of a spectroscopic analysis of bright stars in the Carina dSph galaxy. We collected low-resolution FORS2 VLT spectra of ss 200 stars. Our spectroscopic targets have been selected among the evolved Carina stars, in particular we selected low-mass, old Red Giant, Asymptotic, and Horizontal Branch stars, as well as intermediate-age stars of the Red Clump. We present preliminary estimates concerning the radial velocities of old and intermediate-age populations. 

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