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Re: [lx90] Re: Polar alignment....magnetic interference

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  • Bert Denovan
    Well my flabber is gasted! You note of course that Variation is used mostly by mariners. That s me. Never heard of the other gibberish. And it seems that a
    Message 1 of 12 , May 1, 2003
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      Well my flabber is gasted!
      You note of course that 'Variation is used mostly by mariners.' That's me. Never heard of the other gibberish.
      And it seems that a positive bearing is West! As the saying goes: 'If you assume you make an ASS out of U and ME!'
      I will write out 500 times 'I must not assume'.
      So if this is the case and your 'declination' is -11 and that means East then you ADD Eastings to get true North. In your case 000 - 11 = 011 compass. Or 11 degrees East of North.
      From now on this Ancient Mariner will retire from the field hurt. (With a painful torpedo in his side.) :o)
      Bert
      ----- Original Message -----
      From: Mark
      To: lx90@yahoogroups.com
      Sent: Thursday, 1 May 2003 2:44
      Subject: Re: [lx90] Re: Polar alignment....magnetic interference



      Hi Bert,

      This is the website I got it from. Check it out.

      http://www.geomag.nrcan.gc.ca/geomag/magdec_e.shtml

      Cheers,
      Mark


      On Thu, 1 May 2003 08:45:07 +0800
      "Bert Denovan" <berjac59@...> wrote:

      > Well, I have never heard of Westings given as plus or minus! Then again it has been a long time since I have been @ sea.
      > I can only assume that -11 = 11 degrees West. Given that CADET says add Eastings then it follows that you subtract West. And that fits in with the -11. It is telling you what to do.
      > Therefore you need to subtract the VARIATION (where did declination come from? This means vertical angle.) So True North on your magnetic compass is 360 - 11 = 349 degrees. ie 11 degrees West of North.
      > Good luck, Mark. :o)
      > Bert
      >
      > ----- Original Message -----
      > From: Mark
      > To: lx90@yahoogroups.com
      > Sent: Wednesday, 30 April 2003 8:33
      > Subject: Re: [lx90] Re: Polar alignment....magnetic interference
      >
      >
      >
      > My brain hurts. OK, so according to thre GSC website, my
      > magnetic declination is -11 degrees. Does that mean True North
      > is 11 degrees West of where magnetic north is?
      >
      > Mark
      >
      >
      > On Wed, 30 Apr 2003 14:16:50 +0800
      > "Bert Denovan" <berjac59@...> wrote:
      >
      > > Here I go again - can't help myself.
      > > The difference between true and magnetic North is called Variation.
      > > The difference between magnetic North and the compass affected by ferrous metals and magnetism nearby is called Deviation.
      > > Both have to be applied if you want to convert magnetic (Compass) to true.
      > > There is an old mnemonic using the word CADET. It goes like this - Compass to True Add East. Swing from 'C' to 'T' (Compass to True), then 'AD' (add) and 'E' (East). And it follows that you subtract West.
      > > So if your local Variation is 15E you would find true North @ 015 degrees on the magnetic compass. Then if you are able to determine the Deviation (which changes with the direction you are pointing), and it was 10 degrees West your bearing of 015 degrees is to be altered to 005 degrees or 5 degrees East of North.
      > > Simple isn't it! :o)
      > > Dick is right, degaussing is the best way but even if you have your car near you it will affect the Deviation.
      > > And Dick, degassing a warship is a much more tedious affair. :o)
      > > Sailor Bert
      > > Ravenswood
      > > Western Australia
      > >
      > > ----- Original Message -----
      > > From: mworsley
      > > To: lx90@yahoogroups.com
      > > Sent: Wednesday, 30 April 2003 5:22
      > > Subject: [lx90] Re: Polar alignment....magnetic interference
      > >
      > >
      > > Cliff,
      > >
      > > I think it may be the large steel bolt that the "wedge nut" that houses the
      > > compass screws down onto to hold the wedge in place. I have noticed it on
      > > my scope as well. Your idea of measuring the additional error and just
      > > adding it (or subtracting it as the case may be) to the magnetic deviation
      > > is probably the easiest solution.
      > >
      > > Regards,
      > >
      > > Mike Worsley
      > > Fareham
      > > Hants
      > >
      > > >From: "coh5789" <cohill1@...>
      > > >Subject: Polar alignment....magnetic interference
      > >
      > > >Hi Folks,
      > > > I recently bought the Meade Wedge and adapter plate for my LX-90.
      > > >Everything seems to work well and I've benefited greatly from Jan's
      > > >page (thanks for all the work Jan!). One problem I've encountered and
      > > >have not seen mentioned here is the fact that the steel in the tripod
      > > >seems to put about a 10 degree bias on the compass that comes with the
      > > >wedge. I've confirmed this with a separate hiking compass and can see
      > > >that as soon as I get near the top of the tripod, the bias (toward the
      > > >East occurs). I'm not too surprised there is an effect but the tripod
      > > >seems pretty symmetric so I'm surprised to see the 10 degree bias. As
      > > >long as it reproducbile, I think I can compensate by changing the
      > > >'true north' and 'magnetic north' settings on my compass from the
      > > >actual 12 degrees to something more like 22 degrees. Has anyone else
      > > >seen this problem, and does this seem like a reasonable solution? If
      > > >I don't make this adjustment, my setup is not pointing close enough to
      > > >Polaris to make the intial wedge setup adjustments.
      > > > thanks, Cliff
      > >
      > >
      > >
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