Well . . it was clear to me?????

Subject: Compass dip - questions for the southern Hemisphere people.
From: "Schoonertrash"
Date: 11/28/2003 18:52 Pacific Standard Time
Message-id:

Well . . it was clear to me?????




I'd be curious as to what they had to do in Australia to fix the "dip" problem,
plus, curious how they "balance" small yacht compasses to make them good, world
wide.

As Doug mentioned the cost of doing that is prohibitive. Much easier to get
two compasses. When you see the need, and it will be very apparent. Switch
to the other one. Then you only have to swing the compass for correction
which is not all that difficult. Remember you now have things like GPS to
help you out. Or use a star sight for N. and S. Figure amplitude on the
sun's rising and setting to find E. and W. Sounds much more intimidating
that it really is.

MST

One day left.

Subject: Compass dip - questions for the southern Hemisphere people.
From: "Schoonertrash"
Date: 11/29/2003 10:31 Pacific Standard Time
Message-id:

As Doug mentioned the cost of doing that is prohibitive. Much easier to get
two compasses. When you see the need, and it will be very apparent. Switch
to the other one. Then you only have to swing the compass for correction
which is not all that difficult. Remember you now have things like GPS to
help you out. Or use a star sight for N. and S. Figure amplitude on the
sun's rising and setting to find E. and W. Sounds much more intimidating
that it really is.

MST

One day left.


If that's directed at my response, I'd have to disagree.
Since balanced compasses are available, I'd consider it a better investment to
go for the single, potentially better compass, rather than two cheaper models
(which may end up costing about the same).
Naturally, there are always advantages to having two.....and even though it may
be unbalanced, doesn't mean it won't work.
I'd still be curious as to what they had to do to that ship compass to correct
it, as I've never heard of any problems with dip on one of these (might have
something to do with hanging the magnets well below the compass card and pivot)
Taking azimuths/amplitudes/polaris, should be a normal occurence for anyone
doing serious offshore work..... BG devising methods to get accurate ones on
many small boats, is another story

We're moving soon and will be within cell phone range one more time before
heading 'way' out. I'll make a point of asking some tech questions and
report back.

MST

Schoonertrash wrote:

Well . . it was clear to me?????

Massive iron deposis in Canada have nothing at all
to do with compass dip. It's only that the earths
surface is not parallel to the lines of the Earths
magnetic force. Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.

You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.

BTW in a couple of "around the world" sailing
books, the skipper/author talks about either
correcting for compass dip or switching compasses.
One of them is 'My Old Man & The Sea' which is a
good read all in itself; but they planned to take
three compasses with them (on a 25' boat no less)
and in the last minute rush, forgot. So they
disassembled their compass and remounted the
magnets to correct for dip. Interesting book, I
gave my father a copy.....

Fresh Breezes- Doug King

DSK wrote:

Massive iron deposis in Canada have nothing at all
to do with compass dip. It's only that the earths
surface is not parallel to the lines of the Earths
magnetic force.

100% correct.

Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.

Not really, the region of zero dip wanders about 12 degrees north and
south of the equator. Check out Chart 30 for this info?


You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.

Dip is also affect by anolmalies.


Cheers MC

The_navigator© wrote:



DSK wrote:

Massive iron deposis in Canada have nothing at all
to do with compass dip. It's only that the earths
surface is not parallel to the lines of the Earths
magnetic force.


100% correct.

I exaggerated. It's about 50%

Cheers MC

Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.


Not really, the region of zero dip wanders about 12 degrees north and
south of the equator. Check out Chart 30 for this info?


You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.


Dip is also affect by anolmalies.


Cheers MC

"The_navigator©" wrote in message
...
....

Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.

Not really, the region of zero dip wanders about 12 degrees north and
south of the equator. Check out Chart 30 for this info?

He was refering to the Magnetic Equator.



You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.

Dip is also affect by anolmalies.


Dip and variation are the same phenomenon, measured on different axis.

Jeff Morris wrote:

"The_navigator©" wrote in message
...
...

Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.

Not really, the region of zero dip wanders about 12 degrees north and
south of the equator. Check out Chart 30 for this info?


He was refering to the Magnetic Equator.


Not as I read it he wasn't.


You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.

Dip is also affect by anolmalies.


Dip and variation are the same phenomenon, measured on different axis.

What is the phenomenon you have in mind?

Cheers MC