Gary, have confirmed via
https://www.magnetic-declination.com/# that 11.3 deg is correct for Gold Coast.
The problem seems to be with my code, which produces different results depending on whether the values for lat & lon are enclosed in quotes or not, and the manner in which the variables are declared:
ob.lon, ob.lat, ob.elevation = -28.00274, 153.42999, 0
produces 286 deg
ob.lon, ob.lat, ob.elevation = '-27.9985', '153.4227', 0
produces 62 deg
ob.lon, ob.lat, ob.elevation = -27.9985, 153.4227, 0
produces 286 deg
ob.lat='-27.9985'
ob.lon='153.4227'
produces 299 deg
So, 299 - 11.3 gives me an angle to magnetic north of 287.7 deg or 72.3 deg., which seems about right based on observation. I'll pull out a compass to confirm if the skies clear.
Thanks for your help everyone!
