# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Finding Longitude from LST
From: Duane Smith
Date: 2020 Aug 16, 22:15 -0700

The point I was trying to make is, that you can get LST by measuring the position angle or clock angle starting directly above Polaris as zero. Then going Counter Clockwise. 90 degrees West is 6hours. If a star is on your meridian, the stars Longitude is your Longitude. Likewise the stars RA is your LST. What you try to measure or guesstimate is how many hours minutes seconds have passed since the star was on your meridian directly above Polaris. If Kochab is on your meridian, your LST is 14h50m37s the RA of Kochab. If Kochab is at clock position 7:30, then LST is 7h30m + 14h50m37s, 22h20m37s. Now compare this with GST to get Longitude. If GST is less than LST, add 24 to GST. GST must always be greater than LST. If Kochab is at clock position 13h20m, then LST is 13.20+14.5037 equals 28.1037, subtract 24 LST is 4.1037. What I'm trying to get at is you can get Longitude within a few degrees, at night ALL night, no sextant, no sight reduction tables or forms. Take six sights, get six Longitudes in less than ten minutes. Throw out any you don't like. Average the rest. How hard is it to drop a plumb line through Polaris to see if a star is on your meridian, upper or lower? Hold a carpenter level just below Polaris to see if a star is exactly East or West of Polaris. With only these 4 points for reference you can get within a few minutes of true time. Make a circular clock face with clear plastic, mark every 15 degrees for the hours, twenty minute marks between the hours. Put a hole  in the exact center, center Polaris in the hole, put an hour mark straight up. Hope you are getting the idea. Take Menkalinin over by Capella for example, RA 6h01m03s. Above Polaris, LST is 6.0103. West of Polaris, LST is 12.0103. Below Polaris, LST is 18.0103. East of Polaris LST is .0103.

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