A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2018 Sep 21, 08:00 -0700
You wrote of lower transits "this is nearly irrelevant to practical navigation". True but there are some situations where it has a place. Reginald James writes in the appendix of Shackleton's book "South",
‘The chief uncertainty in this measurement is that introduced by the refraction of light by air. At very low temperatures, the correction to be applied on this account is uncertain, and, if possible, observations should always be made in pairs with a north star and a south star for latitude, and an east star and a west star for longitude. The refraction error will then usually mean out’.
At south polar latitudes the "south star" will generally be below the pole,