(2) Any object with surface brightness too low (much less than about 1% of the night-sky brightness) would only be found when near enough for individual stars to be seen (this is how the Sculptor dwarf galaxy was discovered).
Space-based coronagraphs such as LASCO avoid the sky brightness problem; the next challenge becomes stray light management under the stringent size and weight requirements of space flight.
Thirdly, atmospheric turbulence ("seeing") limits the ability of a telescope to show detail, and sky brightness limits its ability to show faint objects. Poor seeing usually hits large telescopes harder than small ones.
A last thing to consider is the effect of sky brightness. This is not a telescope property, per se, but nevertheless affects what a telescope can do.
Certainly we know that there is obscuring material in the universe and, at first, one might argue that this material could reduce the calculated sky brightness.
If we measure brightness in candle power/meter squared (cd/(cd/m2) the Earth's daylight sky brightness is about 8000 (cd/m2. For example, Jupiter has a surface brightness of around 600 (cd/m2 for light areas.
The star's southerly position has allowed northern observers to use its visibility as a test of the night-sky brightness near the horizon. Scorpius is filled with bright blue-white stars of class B.
Twilight The period of decreasing sky brightness after sunset, or of increasing sky brightness before sunrise. There are three definitions of twilight: Civil Twilight, Nautical Twilight, and Astronomical Twilight.
The encroachment of bright lights onto astronomical observing sights, increasing the sky brightness and decreasing sensitivity to faint deep-sky objects.
References ...
The top one is the original spectra whilst the lower spectrum has been adjusted for sky brightness and the effects of absorption in our atmosphere removed.
the GLOBE at Night program (led by National Optical Astronomy Observatory (NOAO) and the GLOBE Program educational outreach staff) has enabled thousands of citizen-scientists around the world to contribute measurements of their local sky brightness ...
These values are 1-2% of the Cosmic Microwave Background (CMB) radiation (the 2.725 K blackbody). In the S10 notation often used for sky brightness, 14 nW/m2/sr is about 1.4 mbol=10th magnitude stars per square degree.
 See also: Sky, Light, Second, Telescope, Distance
  
|
RSS
