These are all the same thing. It's a lot easier to push a button but if you can get your hands on an up to date almanac you can play around some morning and have some fun. Get out your sextant. It should be adjusted for it's various errors like the "index error" and such and have at it. The steps below can be found in various books.

1) Decide whether you are looking North or South in order to observe the Sun on your meridian - name this 'N' or 'S' accordingly - if the sun is north of you, you would just label it 'N'. 2) Correct for dip (the amount the boat is jumping around above (or below) the horizon at the time you plan on taking the shot) to obtain Ho (height of your eve where you are jammed into your favorite corner) and subtract Ho from 90 deg. to obtain ZD. 3) Now... name this ZD OPPOSITE to the sign in step 1. If you were looking N then you just name ZD 'S' and vice versa. 4) Get your little orange Almanac again and find the declination (The "declination angle", which would be "d", changes with the seasons due to the tilt of the Earth on its axis) mark it down and check whether it is 'N' or 'S'. 5) OK, now add OR subtract line (4) and (3) if they are the SAME sign (that would be both 'N' or both 'S') add. OTHERWISE (if opposite signs), subtract the smaller from the larger. 6) The result is your latitude - It only gets squirely close to the equator because it's named by the larger quantity. That would be the difference when the numbers are subtracted in step 5. If you added in step 5, the sign is the sign common to both. If you are off the middle of California, unless you have been drinking, you should know that you're North and not South.

There are plenty of forms you can get that that will help walk you through the steps. I have them but I have to be honest and say that I left all that stuff in storage and just have extra batteries and GPS's. Besides, using a sextant is really as much of an art as a skill and if you don't use it you loose it. I would most likely end up in Machu Pitchu. Hey, it's stone age stuff but it's still fun if your life doesn't depend on it. Other wise, it ain't fun...