How does one compute the rise time and fall time of a star?

I need the general case, that is, the inputs are the right ascension and declination of the star and the longitude and latitude of the observer. I found a few tables on the internet, but I need the equation or an on-line calculator.How does one compute the rise time and fall time of a star?It's not exactly trivial.



The altitude a of a star, given declination 未, latitude f, and hour angle H, is:



sin(a) = sin(未)sin(f) + cos(未) cos(f) cos(H)



Plug in 0 for a to find the hour angle H at which the star is on the horizon. When H is expressed in hours, the star will rise and set H hours before/after it reaches the meridian, at a sidereal time equal to its RA. So the rising time will be RA-H and the setting time will be RA+H in local sidereal time.How does one compute the rise time and fall time of a star?Lola F's equation should be good to about a minute or so. For better accuracy, the equations get *much* more complicated.