A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2020 Aug 16, 15:13 -0700
"This is your Local Sidereal Time. Determine the Greenwich sidereal time of the sight."
Yes, Local Apparent Time (what I like to call sundial time) and Local Sidereal Time are directly observable things. Then to get longitude, you compare your local time with Greenwich Time. That's all you're doing here. You have hit upon an important insight in understanding longitude, but it is not an independent method for determining longitude. The final product is still dependent on knowing Universal Time, also known as GMT, Greenwich Mean Time.