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22 votes

Why was Jupiter so bright; is it the "phase"?

tl;dr: There's about a 1.4 mag oscillation due to $1/r^2$ effects and only a very tiny residual due to illumination angle. I went to JPL's Horizons and extracted the distances between Jupiter and the ...
uhoh's user avatar
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18 votes
Accepted

Why was Jupiter so bright; is it the "phase"?

Jupiter appears particularly bright because it is close to Earth at the moment, it is also high in the sky (in the Northern Hemisphere). However its brightness doesn't vary that much. Jupiter reached ...
James K's user avatar
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3 votes
Accepted

How bright in the night sky would J0529-4351 (brightest quasar ever found) be if it were in our galaxy?

The (boldly titled) omnicalculator can do luminosity calculations. At 500 trillion solar luminosities, this object would have an absolute magnitude of -32, and if placed at 26000 light years distance,...
James K's user avatar
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3 votes

Human Brightness perception and contrast

After some time I found the answer: Actually the CIELAB definition in Figure 1 in my question and the Grayscale standard display function in Figure 2 are quite similar, if the x and y axes of the ...
Charles Tucker 3's user avatar
3 votes
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Does the reflected light from Earth boost Venus' apparent magnitude when it is seen transiting the Sun?

Let's collect some data: Earth has an absolute magnitude of -3.99 Venus has an absolute magnitude of -4.4 (Source Wikipedia Venus and Wikipedia Earth) Absolute magnitude equals the apparent ...
Ralf Kleberhoff's user avatar
3 votes

Standard definitions (ISO?) about subjects related to light emitted by stars

I think your last sentence summarizes perfectly units in astronomy: it seems like a huge mess. Your table shows correctly some various units for measuring "things that emit light", but there ...
pela's user avatar
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2 votes

Visible angular size

In general this is not true. Most celestial objects appear as points of light to the naked eye, and don't have any apparent size. (Though your brain might conflate "bright" with "near&...
James K's user avatar
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1 vote
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How bright would an object need to be in order to block out stars at night?

About magnitude -17, or about 100 times brighter than the moon now. I've found reference to the sky brightness at full moon as being about magnitude 18 per square arcsecond (and equivalent to light ...
James K's user avatar
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