Bubble Sextant – To my knowledge, there is no actual nautical sextant for FS9 or FSX; therefore, it is necessary to use Dave Bitzer’s and Mark Beaumont’s “Bubble Sextant.” Since we are using FSX as our virtual world, we will use Kronzky’s enhanced Bubble Sextant and adapt its use to our needs. There is a limited model for FS9 too (see below).
First, a sextant was/is a tool in navigation which measures the angle of a celestial body (Sun, Moon, stars) from the horizon. The viewport has a split view with a configuration of mirrors in the same view. One view is of the celestial body, and the other is of the horizon. It takes some skill to ensure the sextant is held steady. Sliding the arm along the scale (at the bottom of the sextant) until the view of the celestial object “sits” on the view of the horizon. The scale shows the angle measurement. When taking a “shot” (a sighting) is done correctly at the exact time and height the angle identified on the sextant equals the latitude of the observer. This tool was not only for use on the seas. It works as long as one can see the horizon on a large lake. One can use the sextant on land in combination with a small pool of liquid as a reflective surface like Mercury or “Quicksilver.” This combination works because the liquid seeks its level like water in a glass, but cut the reading in half. Due to the impracticality of using a reflecting pool device and the nautical sextant in an aircraft, necessity required the invention of the bubble sextant. It worked by watching the position of a bubble as a “horizon.” Have you seen a bubble or “spirit” level used in construction? It is the same principle. A centered bubble in the viewport of the bubble sextant indicated the device was level, resulting in an accurate measurement of the angle to the celestial body. FYI – the geometry is based on a circle. The device is called a “sextant” because it measures one-sixth of the circle. There are also “quadrants” which measure one-fourth (90 degrees) and “octants,” and they measure one-eighth (45 degrees) of the celestial arc. Thanks to the talents of Bitzer, Beaumont, and Kronzky we have a working model with some caveats for simulated reality:
- Entry of S latitude and w longitude “Assumed Position” must be negative numbers. If you take a shot and you do not see the green “Sun” in the viewport (day) or white “stars” (night) then check to be sure your positives and negatives are correct.
- There are three “bubble” sizes available for the viewport. I have found the 3rd, or biggest choice allows me to center the celestial object faster, but the smaller ones may work best for you.
- The Bubble Sextant cannot determine if the skies above are cloudy or clear. It will always “see” the green orb of the Sun or the white dots of stars and planets even in solid overcast meteorological conditions. As yourself as navigator, examine the cloud densities and make the call if a sextant shot would be possible. If not, wait until conditions improve. This limitation is what real-world mariners sometimes faced for weeks (months?). All mariners could do was to record ship’s speed, bearing and current estimations and plot the best guess on the chart.
Try to fly from KLAX to PHNL in a transatlantic propliner or jet (without a GPS). It is quite rewarding to see Hawaii come into view after 10 hours of manually-navigated flight. Take a look at these Youtube videos in two parts for a good explanation how to use the Bubble Sextant in a virtual aircraft which works well for water-borne vessels too:
Go here to download the Bubble Sextant:
FS9 – https://flyawaysimulation.com/downloads/files/1021/fs2004-simulated-aircraft-bubble-sextant/
FSX – http://kronzky.info/fs/sextant/index.html