Another low visibility approach, but a nice NDB to line up with.
http://fs-duenna.com/flights/ShowFlight.php?detail=flight&value=4HoM7a0KraPM3l2 XIq6KOYUzY
Attachment 63850Attachment 63851
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For those how are wondering what I’m doing here with the sextant.
The sextant shots explanation. (Note that this is not verbatum out of Dave B or Marks B's very detailed instructions. This is merely an explanation of how I used the sextant on this particular flight)
It passes the time.
(Actually, the whole process takes very little time when everything is set up in the plane. The explanation filled in the boring part of the flight and is what took some time).
Departing at 06:00Z I picked a point 200nm from Dakar in route toGUCY, which should give me an average of 200nm/hour including the climb speed,and turn to course after TO from GOOY etc.
From the USNO website http://aa.usno.navy.mil/data/docs/celnavtable.php I set into the sextant the location I should be in one hour at 07:00Z
Attachment 63852 Attachment 63853
Notice that, on the sextant, I set LAT N12°00’ and LON W15°20’
Attachment 63854
Also after hitting calculate (the second pic) I see that the sun will be at an azimuth (Zn) of 80.9°, or rounded off to 81, set by the course elevation wheel. The elevation (Hc) will be 16°55’ above the horizon set with the fine adjustment wheel on the sextant.
The Center (Spot) of the graph on the sextant is my destination location or where I should be at 08:00Z
The blue line is a reading I took at 07:30z just to get an idea of how I was progressing eastward or longitudinally. The distance read 50nm. The green line was a reading taken at 07:45z and the red line is the reading I took at 08:00z.
So at 08:00z I was right where I wanted to be at that time.
Observations:
1. Being that we’re only 12 degrees above the equator, 1 degree oflongitude is just about the distance of 58nm, or very close to the 60nm at theequator
2. Notice also, on the graph, that the Moon’s azimuth (Zn) is 78.1°andelevation (Hc) is 18° 01.8’ above the horizon as well. Obviously, if it weren’t for the brightnessof the sun we could see the moon as well.
3. Keep in mind that my readings are for April 21, 2012. If you pickan later date the readings will be slightly different.
4. When looking at the sextant graph think of the vertical lines asbeing parallel to the longitude and perpendicular to 90 and 270 degreesrespectfully. When the azimuth of the star, planet, sun or moon are close to anazimuth of (east or west) you’re obtaining accurate longitudinal readings.
5. In retrospect, when the azimuth of the star, planet, sun or moonare close to an azimuth of (north or south) we’re obtaining accurate latitudereadings.
(In the example above the blue, green and red lines are more vertical so thelongitude reading is what’s accurate.)
6. Being that we’re close to the equator, and it’s spring, the sun will not give us an accurate latitude reading any time ofthe day. As we approach the poles, the sun can be used as a tool for reading latitude as long as we take the reading at high noon and ONLY then.
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Dil52
Originally Posted by teson1
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