Having just come off a basic navigation course, celestial is the next logical step. What I’m failing to understand from a 30,000 foot perspective is converting measurements to DMS to obtain a fix. I feel the concept is quite simple, collect at least two measurements from the sextant and this should give you a fix, but how to actually convert those numbers to DMS. Please let me know if I’m way off topic.
For many reasons a sextant reading is not easily converted to DMS to put on a chart as a line of position (LOP). As explained in a simplistic way in this video, we need a way to "get on the chart" which is what the sight reduction process is all about. I encourage you to watch the first several videos in the series which cover the elements of theory and break down the sight reduction process into digestible steps. And don't hesitate to reach out with more questions!
So when you measure the altitude of the sun, the co-altitude is the distance between you and the geographical position of the sun expressed in degrees of the arc of the great circle that runs between those 2 positions?
There are 90 degrees between the horizon (zero degrees of altitude) and your Zenith (directly overhead or 90 degrees of altitude). With a sextant we measure how high above the horizon the body is (its altitude) and the co-altitude is the remaining measurement on that 90 degree arc from horizon to Zenith. Make sense?
This is such a great explanation. I have a question. At 18min 22 sec into the video you plot an assumed LOP using the bearing to the sun from your assumed position. Wouldn't it be more accurate to use your actual bearing to the sun and back up some for the fact that your assumed position was actually closer than your geographic position?
This may become more clear in the next episode, but here's a quick answer to your question. We select an Assumed Position (AP) based on several criteria, but it is typically pretty close to our DR position so we can get both positions onto our chart as described in this episode. In practical terms we consider the bearing to the body to be the same for both positions. Think about how far away celestial bodies are and how little the bearing would change even if we move a few miles in any direction, or at the very least how hard it would be to accurately measure and plot any differences in those bearings given the scale we use on the chart. The bearing to the body is given as part of the answer in the tables, based on the AP. Since we assume the same bearing for both the AP and the spot where we actually took our sight, we only have to compare the difference in the sight values (what we shot at wherever we are vs. what comes out of the tables for the AP...calculating the Intercept). We don't have to worry about the bearing beyond plotting it from the AP.
If someone knew nothing of celestial navigation, this would be quite unclear. I think one needs to do a primer on celestial mechanics before ever talking about DR’s, GP’s, triangles, etc. This is why people find learning celestial navigation so confusing. Thanks.
Thanks for your comment. The course assumes understanding of basic navigational concepts which opens the door to the ideas in this video. The "practical" approach of the course may not be successful for everyone, but I've found it to work for those who start with that base knowledge and ultimately want to practice celestial at sea on a small boat.
So earth is a stationary plane where we measure elevation angles of stars for celestial navigation. Those flat earth elevation angle measurements were used to create the celestial sphere model which is a flat earth with an imaginary sphere of equidistant celestial bodies rotating around it. Got it. Welcome to flat earth!!!
What a load of BS!! Thousands of sailors and navigators know it works and only for a rotating spherical Earth and it has been used successfully for 300+ years. The modern US Navy GPS, the Russian Glonass and the ESA Galileo location systems work in a similar way (with distances, not angles) using an artificial constellation of satellites which orbit the Earth. The celestial sphere is simply a model to project astronomical data onto for ease of calculation. You really don't have a clue as to how it all works!
@@karhukivi The celestial sphere is a flat earth model. The sphere is obviously imaginary but the stationary plane is required for celestial navigation. Welcome to flat earth!!!
@@tbrown3356 Sorry mate, you must be very gullible to have been taken for a ride by trolls. The calculations depend on astronomical data that anyone who has a home telescope will be familiar with. Have you any friends in other parts of the world? - If you have, you can call them on skype or zoom and see that different places are in night time while other parts are in daytime - impossible on a flat earth. The agencies that make maps and marine charts all use astronomical data and a spherical earth. You need to get educated!
@@karhukivi I explained in great detail how celestial navigation works. It uses a horizontal baseline at sea level to measure elevation angles of stars. That's impossible to do with a curved surface (globe earth).
@@tbrown3356 I use celestial navigation on our yacht and it works! We don't need or use "baselines". I'll bet you have never even been on a boat doing an ocean crossing. Do you believe all the rubbish you hear? If I said that Americans don't play baseball, or California is the coldest place on earth, would you believe me? No, because it is easily disproved, just like the flat earth nonsense.
Excellent series I’m watching everyone and RE-watching everyone. Thank You for sharing your knowledge 👏👍
Thanks for watching!
I am so grateful for having found your channel. So well done. You are an excellent instructor. Thank you for sharing your wisdom.
This is fantastic resource for anyone looking to master celestial nav:) well done!
Thanks for the note, hope you enjoy the series!
Thank you so much. You are a very good teacher.
THANK YOU! That was a great Intro!
Thank you so much.
Good lesson
Having just come off a basic navigation course, celestial is the next logical step. What I’m failing to understand from a 30,000 foot perspective is converting measurements to DMS to obtain a fix. I feel the concept is quite simple, collect at least two measurements from the sextant and this should give you a fix, but how to actually convert those numbers to DMS. Please let me know if I’m way off topic.
For many reasons a sextant reading is not easily converted to DMS to put on a chart as a line of position (LOP). As explained in a simplistic way in this video, we need a way to "get on the chart" which is what the sight reduction process is all about. I encourage you to watch the first several videos in the series which cover the elements of theory and break down the sight reduction process into digestible steps. And don't hesitate to reach out with more questions!
So when you measure the altitude of the sun, the co-altitude is the distance between you and the geographical position of the sun expressed in degrees of the arc of the great circle that runs between those 2 positions?
There are 90 degrees between the horizon (zero degrees of altitude) and your Zenith (directly overhead or 90 degrees of altitude). With a sextant we measure how high above the horizon the body is (its altitude) and the co-altitude is the remaining measurement on that 90 degree arc from horizon to Zenith. Make sense?
@@thenavstation That makes sense, thank you
This is such a great explanation. I have a question. At 18min 22 sec into the video you plot an assumed LOP using the bearing to the sun from your assumed position. Wouldn't it be more accurate to use your actual bearing to the sun and back up some for the fact that your assumed position was actually closer than your geographic position?
This may become more clear in the next episode, but here's a quick answer to your question. We select an Assumed Position (AP) based on several criteria, but it is typically pretty close to our DR position so we can get both positions onto our chart as described in this episode. In practical terms we consider the bearing to the body to be the same for both positions. Think about how far away celestial bodies are and how little the bearing would change even if we move a few miles in any direction, or at the very least how hard it would be to accurately measure and plot any differences in those bearings given the scale we use on the chart. The bearing to the body is given as part of the answer in the tables, based on the AP. Since we assume the same bearing for both the AP and the spot where we actually took our sight, we only have to compare the difference in the sight values (what we shot at wherever we are vs. what comes out of the tables for the AP...calculating the Intercept). We don't have to worry about the bearing beyond plotting it from the AP.
@@thenavstation thank you I have wanted to learn celestial navigation for years and this is the most clear explanation I have ever seen.
is there a number 1 video? oh I see it now.
If someone knew nothing of celestial navigation, this would be quite unclear. I think one needs to do a primer on celestial mechanics before ever talking about DR’s, GP’s, triangles, etc. This is why people find learning celestial navigation so confusing. Thanks.
Thanks for your comment. The course assumes understanding of basic navigational concepts which opens the door to the ideas in this video. The "practical" approach of the course may not be successful for everyone, but I've found it to work for those who start with that base knowledge and ultimately want to practice celestial at sea on a small boat.
Basic knowledge of Lat/long is required, put you big boy pants on and study.
@@GMT-plus-seven I taught myself celestial navigation. I didn’t find this a helpful resource. No need to be snarky. Take care.
So earth is a stationary plane where we measure elevation angles of stars for celestial navigation. Those flat earth elevation angle measurements were used to create the celestial sphere model which is a flat earth with an imaginary sphere of equidistant celestial bodies rotating around it. Got it. Welcome to flat earth!!!
What a load of BS!! Thousands of sailors and navigators know it works and only for a rotating spherical Earth and it has been used successfully for 300+ years. The modern US Navy GPS, the Russian Glonass and the ESA Galileo location systems work in a similar way (with distances, not angles) using an artificial constellation of satellites which orbit the Earth. The celestial sphere is simply a model to project astronomical data onto for ease of calculation. You really don't have a clue as to how it all works!
@@karhukivi The celestial sphere is a flat earth model. The sphere is obviously imaginary but the stationary plane is required for celestial navigation. Welcome to flat earth!!!
@@tbrown3356 Sorry mate, you must be very gullible to have been taken for a ride by trolls. The calculations depend on astronomical data that anyone who has a home telescope will be familiar with. Have you any friends in other parts of the world? - If you have, you can call them on skype or zoom and see that different places are in night time while other parts are in daytime - impossible on a flat earth. The agencies that make maps and marine charts all use astronomical data and a spherical earth. You need to get educated!
@@karhukivi I explained in great detail how celestial navigation works. It uses a horizontal baseline at sea level to measure elevation angles of stars. That's impossible to do with a curved surface (globe earth).
@@tbrown3356 I use celestial navigation on our yacht and it works! We don't need or use "baselines". I'll bet you have never even been on a boat doing an ocean crossing.
Do you believe all the rubbish you hear? If I said that Americans don't play baseball, or California is the coldest place on earth, would you believe me? No, because it is easily disproved, just like the flat earth nonsense.