Please could you let me know a (basic) formula for calculating at what time a star would become visible of an evening in clear weather conditions. I presume the formula would involve the stars apparent magnitude, the location of the observer, and how far the sun has dipped below the horizon (so, the sky's limiting magnitude). Working with these three parameters, I guess there must be a simple enough formula, however I cannot find it! Could you help with this? For example, assuming clear weather and good eyesight, how could I calculate at what time the star Deneb will become visible on the 1st May 2019 for a rural location?

I am asking this as I want to create an art piece where something happens each time a new star (or stars) becomes visible around twilight time....

Thank you.

  • $\begingroup$ You may want to try online tools that compute what you need for you — when twilight begins and when the brightest planets and starts rise and set. For example: skyandtelescope.com/observing/interactive-sky-watching-tools $\endgroup$ – Oleg Muir Lou Goff Mar 14 '19 at 22:23
  • $\begingroup$ Weaver 1947 ends with a graph of limiting unaided-eye magnitude vs. solar zenith angle. You might want to model the effect of the moon too. $\endgroup$ – Mike G Mar 17 '19 at 17:56

Maybe that piece shouldn't consider necessarily individual stars rising from the East but entire constellations/parts of constellations. Trying to express the sky movement as a whole sounds really nice to me. There could be planets setting (like Mercury or Venus right after dusk in the West) or others rising (quite bright) Jupiter, Saturn Mars. Even large deep sky objects portrayed there could be amazing - like the Orion Nebula, Andromeda Galaxy, The Double Cluster, Pleiads, M44 Cluster, meteors, etc. I found a good expression of items of the night sky here.

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  • $\begingroup$ This doesn't seem to answer the question. $\endgroup$ – Mike G Mar 18 '19 at 15:26

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