Quote:
Originally Posted by LewisM
Carlton, yes 180 T is 180T, which equates in this case to magnetic south being 190.8. But compasses measure magnetic so to find true as we need to for Astro you SUBTRACT the variation to get an indicated compass bearing for True South.
We don’t use magnetic at all in Astronomy so we need to find TRUE. A compass shows 180 magnetic, do true is 10.8 degrees LESS in this example, being a compass bearing of 169.2
If you set up compass 180 plus variation you will be way off polar aligned.
On a map using a protractor you are measuring TRUE. The maps show lines of mag var’n which in the eastern states you add to the true to get the magnetic bearing.
Again we need to find true not magnetic. You reverse the nav procedure.
Or does this explain HMAS Melbourne’s grand misfortunes?  |
Sorry but, I'm not following your logic Lewis... When you take a compass bearing (magnetic) you add easterly variation to plot it as a true bearing... Eg: magnetic bearing of 080 becomes 090 (if variation is 10E) in order to plot it as a true bearing... To convert a true bearing to magnetic you subtract it from 090 to get a compass bearing of 080...
Okay... I see where you are going with this now... You're explaining to Leon what the bearing should read on his magnetic compass... I think... Penny may have just dropped... Please confirm...😁