NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Polaris isn't so easy!
From: Jim Thompson
Date: 2004 Apr 6, 08:28 -0300
From: Jim Thompson
Date: 2004 Apr 6, 08:28 -0300
To summarize messages that I've been receiving on and off the list: 1. Polaris is dim enough that it has to be shot later in twilight, reducing the window of opportunity because the horizon is worsening rapidly then, even as Polaris is becoming brighter. 2. An artificial horizon (pan of oil) can work, with practice, but it is not easy to use initially. 3. Optimize environmental factors: 3a. Pick a spot with minimal urban light pollution. (I was standing beside a lighthouse!!). 3b. Dark adapt eyes carefully, and keep them dark adapted (red flashlight). 3c. Use AH when there is no wind. 4. Use a telescope. The 2.5 power will work, but higher power is better, though not necessary. 5. Use a split horizon rather than whole horizon. 6. Preset the sextant for predicted altitude, or reverse the sextant. I have been trying to bring Polaris down to the horizon, which is my usual practice with bodies. I was losing it about a third of the way to the horizon. 7. Polaris is easy to find at our latitude because it is the first star to appear at 45 degrees due north and is "all alone" for a while, until its neighbours appear. But the neighbours are easy pointers anyway. 8. Practice, practice, practice. With time shooting Polaris will seem easy, but not the first night out, or even the second. http://jimthompson.net/boating/CelestialNav/Polaris.htm Jim Thompson jim2@jimthompson.net www.jimthompson.net Outgoing mail scanned by Norton Antivirus -----------------------------------------