Again & again, this is the ONE series of videos on celestial navigation that I keep coming back to. I have found no better source of information on this subject. Thank You.
Too cool!!! Shot Sirius and calculated a near perfect azimuth 124.5 and 12.9 min towards. Of course, I'm not moving (yet) and I used a cheap bubble horizon to pick a horizon target during daylight that I could use at night. I think I'll run over to the beach tomorrow night and do it again.
Awesome :) I always like to hear good sea (land?) stories! Good work, keep it up! I am reminded of what Jack London said when he learned celestial navigation in his book "Voyage of the Snark": "I did it; with my own hands I did it. I can travel alone, without any nurse of a sea-captain to guide my steps across the seas. I may not fly to other stars, but of this star I myself am master."
Bubble sextants don't need a horizon. The bubble sight allows the sextant to be level during the sight. And, you can not get an Azimuth from a Sextant. You would need a compass to do that. The Az listed in the 229 is the corrected azimuth based of your interpolated position and is used in plotting your LOP. The Towards/Away aspect is measured along that Az from your DR resulting in a LOP (90deg from the Az line). If you wish to perform an Azimuth and obtain a correction for your compass, you use a separate method.
Actually, the First Point of Aries is not a fictitious point related to the constellation of Aries. They are separate. The 1st point of Aries is known as the GHA of Aries and is where the suns declination passes from south to north in the spring. This point on the equator (and in turn the Celestial Equator) is the 1st Point of Aries. It is then 'fixed' on the Celestial Sphere and moves with the Sphere as it rotates. The hourly position is listed under GHA Aries in the Nautical Almanac. It changes each year, and the amount of change is pretty much constant and is listed in the Nautical Almanac under the topic of using the yearly volume in future years by adding this change to the following years (This allows use of this years N.A. for next year and the next, so on by adding the change amount). The SHA of the 57 Navigational Stars are then added to the GHA of Aries providing the result as the GHA of the star.
Hi! may i ask, from where is the AP Longitude based, on the gps during the actual sight of the body? i notice that the longitude you used to calculate the LHA is different from your DR. What about the AP Latitude, where did you based it? Please help, i am confused. thanks in advance.
AP Longitude: Estimate your current position using ded reckoning. Change your DR longitude to match the decimal minutes for the GHA, so that when you subtract your DR longitude from GHA, there are no minutes left over. This makes using the sight reduction tables much easier, because you don't have to interpolate. You can, however, interpolate degrees of bearing Zn if you want extreme precision, although this usually isn't necessary. AP Latitude: Estimate your AP latitude by rounding your DR latitude to the nearest degree. This will enable you to use the sight reduction tables. That said, you can actually just use your DR position, rather than your AP, if you are using the equations to solve the spherical triangle, rather than using the sight reduction tables. This is more precise, though introduces more opportunities for error. It's best to learn both methods, in my opinion.
Again & again, this is the ONE series of videos on celestial navigation that I keep coming back to. I have found no better source of information on this subject. Thank You.
Too cool!!! Shot Sirius and calculated a near perfect azimuth 124.5 and 12.9 min towards. Of course, I'm not moving (yet) and I used a cheap bubble horizon to pick a horizon target during daylight that I could use at night. I think I'll run over to the beach tomorrow night and do it again.
Awesome :) I always like to hear good sea (land?) stories! Good work, keep it up! I am reminded of what Jack London said when he learned celestial navigation in his book "Voyage of the Snark":
"I did it; with my own hands I did it. I can travel alone,
without any nurse of a sea-captain to guide my steps across the seas. I may not fly to other stars, but of this
star I myself am master."
Bubble sextants don't need a horizon. The bubble sight allows the sextant to be level during the sight. And, you can not get an Azimuth from a Sextant. You would need a compass to do that. The Az listed in the 229 is the corrected azimuth based of your interpolated position and is used in plotting your LOP. The Towards/Away aspect is measured along that Az from your DR resulting in a LOP (90deg from the Az line). If you wish to perform an Azimuth and obtain a correction for your compass, you use a separate method.
Actually, the First Point of Aries is not a fictitious point related to the constellation of Aries. They are separate. The 1st point of Aries is known as the GHA of Aries and is where the suns declination passes from south to north in the spring. This point on the equator (and in turn the Celestial Equator) is the 1st Point of Aries. It is then 'fixed' on the Celestial Sphere and moves with the Sphere as it rotates. The hourly position is listed under GHA Aries in the Nautical Almanac. It changes each year, and the amount of change is pretty much constant and is listed in the Nautical Almanac under the topic of using the yearly volume in future years by adding this change to the following years (This allows use of this years N.A. for next year and the next, so on by adding the change amount). The SHA of the 57 Navigational Stars are then added to the GHA of Aries providing the result as the GHA of the star.
That is all correct, thanks for the explanation.
Hi! may i ask, from where is the AP Longitude based, on the gps during the actual sight of the body? i notice that the longitude you used to calculate the LHA is different from your DR. What about the AP Latitude, where did you based it? Please help, i am confused. thanks in advance.
AP Longitude: Estimate your current position using ded reckoning. Change your DR longitude to match the decimal minutes for the GHA, so that when you subtract your DR longitude from GHA, there are no minutes left over. This makes using the sight reduction tables much easier, because you don't have to interpolate. You can, however, interpolate degrees of bearing Zn if you want extreme precision, although this usually isn't necessary.
AP Latitude: Estimate your AP latitude by rounding your DR latitude to the nearest degree. This will enable you to use the sight reduction tables.
That said, you can actually just use your DR position, rather than your AP, if you are using the equations to solve the spherical triangle, rather than using the sight reduction tables. This is more precise, though introduces more opportunities for error. It's best to learn both methods, in my opinion.
Yes,. The aLat and aLong is your DR position.
Super amazing!!
Thanks For your amazing video and sharing it