t] is defined as that fraction of a small-surface-area element that reflects sky temperature such that the remaining fraction reflects the apparent temperature of the terrain, then the apparent brightness
By comparing the apparent brightness
of Type 1a supernovae and pulsating Cepheid stars, the astronomers could measure accurately their intrinsic brightness and therefore calculate distances to Type Ia supernovae in far-flung galaxies.
At the opposite end of the spectrum, you'll find red (Wratten 23A and 25) and orange (Wratten 21) filters very useful when observing Venus--and Mercury as well--high in the sky during daylight hours because these greatly reduce the apparent brightness
of the brilliant blue background sky.
Alphabetically listed profiles detail the stars' names, resident constellations, apparent brightness
as viewed from Earth, distance, luminosity, and significance.
In the course of her spectral studies of stars at Abastumani Astrophysical Observatory, Dolidze noticed groups of hot young stars with similar apparent brightness
and other groups with a seemingly cluster-like distribution of spectral type and brightness (main-sequence).
By comparing this brightness with the star's apparent brightness
in the sky, astronomers can determine the distance to the Cepheid's home galaxy.
Because these supernovas have roughly the same intrinsic luminosity, their apparent brightness
indicates their distance from Earth.
In the 19th century, astronomers learned how to convert a star's apparent brightness
into its intrinsic brightness (luminosity) by measuring its distance using the parallax method.
By measuring the period of a Cepheid and its apparent brightness
, astronomers can deduce the distance to the star and to the galaxy in which it resides.
And that, together with its apparent brightness
, tells us how distant the host galaxy is.
By comparing the true brightness of MB1 to its apparent brightness
in the sky, the researchers can, in theory, determine its distance.
After a summer interlude when ISON was lost in the Sun's glare, its apparent brightness
at recovery in August 2013 further suggested that it might be too small and faint to survive its coming encounter with the Sun.
Ford of the Space Telescope Science Institute in Baltimore, have now used the apparent brightness
of planetary nebulas to obtain a new estimate of the distance to galaxies in the Virgo cluster.
This would be a boon to anyone using one of SBIG's self-guiding cameras and shooting through filters that reduce the apparent brightness
of a guide star.