Problem with radian and degrees resulting in error Hey all I'm trying to calculate the declination of a star using the following formula. The problem is I keep getting the wrong answer. I believe radians and degrees might be an issue. I'm expecting 0.394254, except it results in 0.306399. I would appreciate if someone had the time to quadtriple check for me? $$\sin{\delta} = \sin{a} \sin{\varphi} + \cos{a} \cos{\varphi} \cos{A}$$ $a$ is altitude: 12.334344 degrees; $\varphi$ is latitude: 52 degrees; $A$ is azimuth: 283.271028 degrees; $\sin{\delta}$ is declination and should equal 0.394254 This is what I have put into Google calculator: sin(12.334344deg)*sin(52deg) + cos(12.334344deg)*cos(52 deg)*cos(283.271028deg) Thank you for your time, it's greatly appreciated.

I have a copy of _Practical Astronomy With Your Calculator, Second Edition_ by Duffett-Smith, and I see an example on page 42 which has numbers close to your example, but a little off. My book has a = 19.333 889 degrees and A = 283.271 667 degrees instead of your values; phi is still 52 degrees. The result given in the book for sin(delta) is 0.394 255, which agrees with the number you quoted except for the last digit. My calculation of sin(delta), using the book's input data, agrees with the book.

So I think there is some mix-up regarding the data, but it doesn't seem to have anything to do with degrees versus radians.