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 Dec 15 answered What are some night sky objects I could see with my Celestron UpClose 20x50 Porro Binocular? Dec 10 comment Coordinate transformations between reference frames in spherical astronomy I am rather sure now. Please correct me if I'm wrong -- edited the answer accordingly. Dec 10 comment Coordinate transformations between reference frames in spherical astronomy Reading this, I am not quite sure if maybe the $r'$ needs to be multiplied instead, since it represents a scaling... Dec 10 answered Coordinate transformations between reference frames in spherical astronomy Nov 22 comment Will Neptune be visible with the naked eye if I am standing on its satellite If my estimates are roughly correct, you will see it in color. $10^2cd/m^2$ are, as I said, in the range of photopic (color) vision of humans. Nov 21 comment What is the distance that the Moon travels during one orbit around the Earth? @leonardvertighel ok, so orbits are linear and/or additive? I was wondering that. I thought it might be a bit more complicated, since orbits are a function of time, and the orbits are not simple, linear functions. Nov 20 revised Will Neptune be visible with the naked eye if I am standing on its satellite added 135 characters in body Nov 20 answered Will Neptune be visible with the naked eye if I am standing on its satellite Nov 20 comment What is the distance that the Moon travels during one orbit around the Earth? Good point! Though I still don't quite know how to calculate it. :) Nov 20 comment What is the distance that the Moon travels during one orbit around the Earth? Yes, I thought of a similar thing. Wikipedia states that the orbit of the Moon around the Sun is convex however, since the Sun's influence is much greater than the Earth's influence. So I don't know if a helix would be a good approximation... Maybe for the Sun/Jupiter/Ganymede system...? Nov 20 comment What is the distance that the Moon travels during one orbit around the Earth? What if you want to know the motion of the moon around the sun? How would you compute that? Nov 20 comment What is the distance that the Moon travels during one orbit around the Earth? Amazing, how close this answer is to the other one, although you did quite a few approximations! Nov 19 comment How are the newly discovered Janus/Epimetheus rings different from the other rings of Saturn? What's the structure like? Nov 19 accepted How does a Bahtinov mask work? Nov 19 comment How does a Bahtinov mask work? If you could add a bit from the linked articles, I would accept your answer: "Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline." Nov 18 asked How does a Bahtinov mask work? Nov 18 comment How can we be sure that we have identified very distant stars correctly? Interesting. So basically we are mostly stuck with parallax measurements in our own galaxy? Nov 17 comment How can we be sure that we have identified very distant stars correctly? I would say that the redshift in the spectrum plays a big role. The absorption lines are kind of like a fingerprint for the elements in the star. If those are shifted, we can calculate the redshift, and hence the distance. Nov 17 awarded Benefactor Nov 16 awarded Scholar