Randy: still not clear on why you checked any distances at the equator. For now I'll assume you used Google Earth to measure the distance from your Assumed Position and your Backyard Position and got 136 nm.
That sounds like a very large error to me. Some things to consider:
- Have you checked that your sextant is properly calibrated?
- Are you using the sun? Are you correcting for semidiameter (you should not if you are using an artificial horizon and bringing the sun down to match his own reflection).
- If you are using a planet or the moon, are you correcting for parallax?
- Are you using a star? Are you sure it's the one you think it is?
I have not been able to take sights from stars, and have not tried planets. The sun is difficult enough for me right now.
The other likely candidate for error is in the calculations somewhere. Are you doing it by hand, or by some computer program, or what?
s/v Laelia - 1978 Pearson 365 ketch
s/v Essorant - 1972 Catalina 27