Alan NV8A wrote:
> But magnetic north is not what we want. We want an indication of *true*
> north.
>
>
Here they are only 6 degrees different. When I was a student pilot they
were the same. (yes it was that long ago). Actually it moves
surprisingly fast and in some areas on the NW there can be 15 to 20
degrees difference. OTOH if you are in the Iron ore country of Upper
Michigan or Minnesota local variations may exceed 30 degrees while the
Isogonic lines indicate 5 or 6 degrees. Idiotic spell checker doesn't
know what Isogonic is.
At any rate, when it comes to HF antennas it's unlikely even 6 degrees
difference is worth worrying about. OTOH when I get the 10" Meade out a
quarter of a degree leaves you wandering around trying to find the
missing star. 20 years ago Polaris ran around a graduated, circular
track in the guide scope. Now it's outside the track unless you very
carefully take that 5 or 6 degrees into consideration. I think the
field of view is less than half a degree. Once you find it Polaris still
follows that track. Even with a focal reducer it takes 4 images to get
the entire moon which is a 1/2 degree sustended angle.
73
Roger (K8RI)
> Alan NV8A
>
>
> On 11/11/08 08:23 pm Randy wrote:
>
>
>> Some day, science will give us a plastic owl, mounted on roller
>> bearings, with an internal magnet aligned
>> with its beak, so the *owl* will point true north.
>>
>
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