10°M = 26°T
Declination East, Magnetic Least
I see Potatoes point and agree, this is difficult to remember and understand. If my declination is 16* east, then I add 16* to the needle: So if I want to face true (map) north, then 0*T = 16*M (0 + 16)... I rotate until the needle is at zero, then rotate again (adding) until it points at the current declination value (16*). But likewise if my BEARING is true north (0*T) then I must rotate the compass dial subtracting the declination value. Not understanding these two methods leads to confusion. Are you adjusting the needle, or the compass dial?
another way I see it is to know where you are in relation to the agonic line. Then its easy to visualize the direction the needle needs to point when adding your declination to your bearing.
I understand the confusion, that's why I said not to think about it too much! When I get into compasses I'll talk about adjustable declination where this doesn't really become an issue, but for the most part you need to remember two things. First off, the rhyme Declination East, Magnetic Least
and then you need to know whether whatever number you're looking at is in Magnetic or True. If you're doing mapwork and pulling a bearing from the map, then it's going to be in true. If you have an undeclinated compass and you're taking a bearing in the real world it will be in magnetic. Once you know which you're working with you can do the math, and just remember that Magnetic should always be LESS than true.
It's a hard thing to articulate through type unfortunately
Raven wrote:The possibility that one might correct for declination in the wrong direction at a critical time has always been on my mind when choosing a compass. I never have made the error, but night travel in an emergency with an injured member of the party dependent on good judgment... Its an old story: 1 problem at a time, simple; two, manageable; three, overwhelming. So any compass I depend on has settable declination -- set at the beginning of the trip or before. Also a mirror, but that's another conversation.
I'll definitely be talking about different types of compass in my next thread. I agree with you though, adjustable declination and a mirror are key if you want to be fully functional out there. I'm trying to keep this stuff a bit
more general than I usually do because I know there are folks on here that travel out of state and do stuff all over, so it's difficult to give hard rules of every scenario.