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0 votes
1 answer
2k views

RA and Dec of the Sun at J2000

I'm in the somewhat awkward position of asking something that, despite me thinking there should be hundreds and hundreds of web pages and datasets showing this particular value, I've been unable to ...
Izhido's user avatar
  • 103
2 votes
1 answer
2k views

how to plot sky map like www.nakedeyeplanet.com with dates tags with planetary motion path

I am curious how to plot planetary motion star chart with date tags like on www.nakedeyeplanets.com by Martin J. Powell. Is there any way to generate images similar like that. What software should ...
M10 Radalpha's user avatar
1 vote
0 answers
98 views

What exactly is a Right Ascension clock and how was one (mounted on a telescope) used in practice, historically?

@MikeG's answer to Why does this Lowell Observatory telescope have so many knobs? What do they all do? explains that item #6 labeled in the image there (and cropped version here) is likely to be a "...
uhoh's user avatar
  • 30.7k
4 votes
3 answers
954 views

Measuring misalignment between two positions on sky

Let's say I have the (RA,Dec) for two positions on the sky. I want to measure the position angle between these two positions. In other words, if I had the Cartesian coordinate vectors for these two ...
quantumflash's user avatar