NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Parallax in azimuth
From: Peter Monta
Date: 2020 May 25, 01:13 -0700
From: Peter Monta
Date: 2020 May 25, 01:13 -0700
One could observe the leading limb of the Moon for an azimuth, but would anyone bother?
Surveyors might. The solar limb is (was?) a traditional observation for azimuth in survey networks; Sokkia's "Celestial Observation Handbook" has some details. Now, the lunar ephemeris is not going to fit into a small booklet, but the principle is there. A theodolite's measurement noise might be 1 or 2 arcseconds, so the correction would matter, provided the surveyor could handle the timing requirement of ~100 ms in UT and has access to an ephemeris.
I played around with daytime stars with the theodolite some time back; it's a lot of fun. As I recall, stars down to magnitude 1.5 were visible in the 50 mm 40x scope; I'm sure an eyepiece camera could do even better. (I tried several times for Polaris and just could not see it.) So there are a fair number of azimuth references available in daytime in addition to the Sun and Moon. (But real surveyors work at night. Atmosphere is steadier.)
Cheers,
Peter
