I am wondering, whether is it possible to use vega-altair-deneb asterism for navigational purpose? Or if there is any geometric relationship of it with Polaris?

Any idea. Thanks


1 Answer 1


Yes, it can be used, but it is not easy.

For the latitude, you usually need to know the Alt of Polaris. You can derive that if you know the Alt of two of the three, but the (spherical geometry) formulas for that are not simple.

For the longitude, you need Greenwich time and the RA of any star. Any star includes Vega, Altair and Deneb ;)

  • $\begingroup$ Well. So, how accurate the result be from above calculation, in comparison to GPS, if the altitude and RA of any star are accurately measured? $\endgroup$
    – kaka
    Commented Jul 18, 2014 at 8:10
  • $\begingroup$ @kaka Depends on how you're doing the above calculation. In general, the error effects from refraction/seeing etc will make it worse than GPS already. If you're going ultra-precise, well, carrying a GPS is easier. $\endgroup$
    – Cheeku
    Commented Jul 18, 2014 at 12:52

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