How can I calculate my longitude and latitude by the position of a star in the sky?

At a particular instant, if I know the exact position of a certain star I can see in the sky in terms of altitude and azimuth (in degrees), and also the exact position of that star in the sky viewed from a different location (of which I know the longitude and latitude) also at that particular instant, how can I work out my longitude and latitude?How can I calculate my longitude and latitude by the position of a star in the sky?for a particular star, you need to know what his 'Right Ascension' and 'Declination' is. Then you have to wait until that star is highest in the sky.



Then if you measure a height of the star e.g. 55 degrees, and suppose the 'Declination' is 15 degrees, then you have a Latitude of 90 + 15 - 55 = 50 degrees.



Now, the rule is that a star with 'Right Ascension' of 0 hours is highest on the sky on midnight and on Sep 21. So with the difference in right ascension, the difference in days from Sep 21, and the difference of time on your watch, you are able to find the 'longitude' where you stand.