... offset my rotator 5 degrees. (my declination was 4*43'...)
What do you think? Did I do it right? ...
That depends, of course, which way
you corrected your rotator display.
If you go the wrong way relative to your magnetic declination (which could be
either + or -) then you'll be 10 degrees off instead.
Does it make a difference? Depends - what is the half power beamwidth of
your antenna array? If it only varies 1dB in 5 degrees, then perhaps not
enough to worry about. You may still have to swing the beam back and forth
a bit to find the best signal, as they might not always arrive exactly where you
The declination correction depends greatly on your location: here on the West
coast it can be 16 to 17 degrees, and up in Southeast Alaska it was over 30 degrees.
And the declination shifts with time: in fact, the rate of change has increased over
the last 20 years or so.
How do you check? The North Star is one way. I lived on a street that ran due
North/South, so basically pointed it up the street (if your antenna is, say, 50' from
the edge of the street, sight it on a point as far up the street as you can see that
is also about 50' from the edge. The required accuracy of that distance estimate
decreases as you go further away.)
Or look choose a landmark that you can see and measure the angle to it from a map,
then use that for your calibration point. Or calculate the bearing (either from the map,
from lat and long, or using a GPS) to a ham friend's house, then have him transmit and
turn your antenna for a peak to see how close your calibration is.
There are lots of other ways, too. The simple declination correction should be the
easiest, as long as you apply it in the proper direction.