Thank you!

Thanks Steve, you're exactly right. GP is defined by Greenwich Hour Angle and Declination. This video starts with declination and then we introduce GHA (and LHA) in the next video in the progression (Polaris). It's part of a series on our website that is also posted (in fragmented fashion) to KZfaq as well. Thanks for watching and for your comment! -Chris

Hi Chris, it is a good question - but being lost at sea would put us in more of a survival situation where we are unlikely to have a sextant and nautical almanac. I recommend a good book called "Emergency Navigation" by David Burch for these kind of situations - there are some cool tips and tricks in there to better understand how the sea and sky can help you know where you are. Thanks!

You're best bet is to have the tabulated values for the sun. Being lost I assume your electronics are down. If you can, keep an eye on the sun thru the noon hours, when it can be seen at 000 or 180 deg, mark the time. If the bearing is north, and the declination is north you know you are south of the tab dec. Fairly simple determination here, not rocket science. Computation from the time will allow the latitude portion of the problem and the GHA of the sun will be your longitude. How accurate the bearing is will have a large degree of how much error is obtained as well. Looking across a magnetic compass is not the best way to obtain a bearing. However, you're lost.. so being somewhere close in the math is way better than nothing at all. No sextant? make something an angle can be taken with. We know the suns dec only gets to about 25-26 deg max at summer and winter, Take a piece of plain paper, fold one corner down, thats 45 deg, fold over again makes 22.5 deg. Hold it to the sun by your eye, make a judgment call on how much angle the suns height is based on the known 22.5 deg fold. Take some time and mark the paper with various angles first. If you are a navigator, you should have a protractor at the chart table, use that as well.

I hate to answer this a year late, but the answer could help someone with the same question. If you have a compass and know what the date is, you can determine which hemisphere you are in based on the Sun's direction from your location. All you need to know is the dates of the spring and autumn equinox.

That is the reason that a Rolex watch is a navigational instrument not a piece of jewelry.

No. Ho is the Observed Height, or Altitude (the angle taken from the sextant). The importance of your Latitude being North or South is because there are 3 cases involved with LAN determination of Latitude. Case 1 DR Lat > Dec Lat = Z Dist + Dec Case 2 DR Lat contrary to Dec Lat = Z Dist - Dec Case 3 DR Lat < Dec Lat = Dec - Z Dist So knowing if you are the same or opposite latitude of the Declination will determine which case applies.

The sight the you took with the sextant should be first corrected right? Same as with the declination by using the d factor

Hello Amran, you will want to be outside shortly before local noon, when the sun is at its highest point. To determine when that is you can do a calculation or just observe the sun with the sextant. in the nautical almanac it lists the times of meridian passage which you can use to determine the time of local noon. Thanks!

Hello Richard - this will depend on your approximate location but the short answer is towards the sun. Depending on your hemisphere and season, it may be north or south, but those are the only two choices. Good luck!

Thanks!

Hi Valenorious, yes indeed that is a great technique to ensure you have the best reading possible. Generally your longitude is changing much slower than the sun's longitude but you are right that is a good way to be super accurate. Thanks!

It's explained beginning 3:26