Nautical Almanac - Sight Reduction Tutorial / Explanation - for the layperson

[@farmerbobross]

Cool to see a fellow Michigander on KZbin. I'm an airplane pilot and learning to use a WWII Astro compass. Your stuff has been helpful. Thanks

[@Billofthenorth1]

Glad it helped. I used to fly also. I think certain interests and hobbies tend to attract people of similar thought.

[@farmerbobross]

I revisited this video because I now have a link A-12 sextant and self teaching sight reduction. In the meantime I’m using EZSights app which is great fun. Thanks again for the good information.

[@Billofthenorth1]

Thanks, I'm self taught as well and always learning.

[@spotremovers]

Thanks for the info about EZsights. I have an A-12 as well. In case you haven't heard of it, check out Bill Morris' ebook on the A-12. When it comes to Sextants, Bill Morris is The Man. sextantbook.com/category/my-bubble-sextant-restoration-manuals/

[@JD-ry1ph]

I am well versed in celestial navigation, a tip to you sir would be to explain how you found the page in increments and corrections in order to find the d correction for the declination, i understood how and where it came from, but others might not. Nice video though

[@brightawe9002]

Exactly

[@brightawe9002]

Please can you help me out?

[@JD-ry1ph]

@@brightawe9002 if you still need help message me on insta @joshdelandri

[@jerryocrow1]

The magic yellow ruler didn't zoom in, but magically appeared making us disconnected. That skill just takes practice in making videos which was disclaimed in the intro. Still, we all grow. Thank you for a good comment.

[@brightawe9002]

lol im here again looking for the same answer after many years lmaoooooo

[@davidmathias1126]

I have a question concerning calculating GHA, Declination, latitude and longitude of the GP of the sun. Let (* = degree and ' = arc/minutes) Question 1: On the first of July 2019 at 12noon, the coordinates of the GP of the sun were Latitude 7* 09.5'S & Longitude 156* 04.2'E (a). Calculate the GHA and Declination of the sun at this time. (b). If the LHA of the sun at the time is 55* 23.1' what is the observer's longitude? Question 2: The Declination of the sun is 17* 19'N, it's GHA is 326* 38'. What is the latitude and longitude of the GP of the sun? Thanks.

[@markprange4386]

It helps to draw the diagrams. Begin with a circle with the North Pole at the center. Draw the 0° longitude, too. 1(a): The Sun's longitude is in the Eastern Hemisphere. GHA is measured to the west. So it is westward past 180° West. But it is well short of a full 360° West. It is short of that by 156° 04.2'. So the GHA of the Sun = (359° 60.0') - (156° 04.2') = 203° 55.8' (West). Dec. = 7° 09.5' South = lat. 1(b): The Sun's LHA in this case is from the observer's longitude WESTward 55° 23.1' to the Sun GP's longitude of 203° 55.8' West. Draw the picture. The observer's longitude must be (203° 55.8' West) - (Δ55° 23.1' ) = 148° 32.7' West. 2.: Lat. = (17° 19' North) = dec. Lon. = (359° 60' West) - (326° 38' West) = 033° 22' East. Get a smooth wooden croquet ball. Sand it smooth, spray paint it with white primer and white paint. Use it as a globe. With a grease pencil mark the Poles, Equator, and the 0° meridian. Maybe the 180° meridian.

[@markprange2430]

1:01 Although clarity is important, the writing in the Almanac is very poor so that it has to be deciphered.

[@arvilmogensen1945]

At the roughly 10 minutes and 47 seconds in the video you find the correction in the table using Fof50 and P of 50

[@arvilmogensen1945]

Sorry, must re-enter. At roughly 10 minutes and 47 seconds in the video we find the correction in the table using F of 50 and P of 49. The correction is a -9. So 48-9= 39. Later the value of 38 is referenced. Am I missing something g?

[@Billofthenorth1]

@@arvilmogensen1945 Check the video about 11:03, there are two corrections to Ho. The first correction is made to Ho of 26 30' - 09' using F and P to obtain it as you stated. Then the second correction is made +08' for an Hc of 26 29' using A and Z2 Hope this helps

[@nassifabdulkadir3727]

I have used this for forty five years. I am looking for the Moon GHA at 1500 hrs GMT on the 22 nd May 2020

[@Billofthenorth1]

try here: thenauticalalmanac.com/2020%20Nautical%20Almanac.pdf

[@jerryocrow1]

Since you asked for comments, I assume you will do an update. If you are true, then next time, add an Excel sheet (and show formulas) as you go to show how to prove/confirm what you are doing and it makes for a great student's log. Thankyou. Also, consider you were a second officer on a commercial airplane. You would have checklists and logs which originate from corporate and are turned into corporate. Your notes would be entered into a computer friendly form (Excel) and turned in after the flight. (Or mid-flight if you crashed.) See how this would be a standard others could follow? You could set an industry standard (write the book, do the lecture circuit, and a consulting business.) Go to it! PS: Do all this at sea, with a storm pitching and surf spraying while your pen runs down the page. (know what I mean) I appreciate your practical approach. Now, take it to the next leve. Thank you.

[@Billofthenorth1]

It sounds like you might be better suited to do that than I. Thanks for the comment.

[@collincourtois8587]

Great job!

[@Billofthenorth1]

Thanks.

[@jaberhasan8346]

Thank you for this. Thats help me

[@Billofthenorth1]

You're welcome. I am far from an expert but I've tried to make this procedure more understandable for people like me.

[@김규민-u2z3g]

thank you so much 🥰

[@johnpinto5095]

The link to the book on Amazon is broken. What is the name of the "best book I've found" on this?

[@Billofthenorth1]

celestial navigation for the clueless

[@shavofairbanks8232]

In the almanac there is another massive list of stars. But on the star finding page it suggest that not all stars can be used with the Consice sight reduction table to reduce a sight. But cant any celestial body's sight be reduced using the table provided??

[@Billofthenorth1]

I think you could do it but you'd need to calculate the SHA for the star in question.

[@shavofairbanks8232]

Billofthenorth1 and i had another thought. could the NAO table be used ad a sort of haversine formula? it calculates distance and azimuth on the celestial sphere but if you replace Lha to your Lha to a place on earth and convert the reduced height to nautical miles then would that be the azimuth and distance to a point on earth?

[@Billofthenorth1]

@@shavofairbanks8232 That would be a good question to ask these guys: thenauticalalmanac.com/Forum/index.php It's a little above my paygrade. I think there is a similar formula in the long term almanac to determine the great circle route, distance and initial heading.

[@markprange2430]

"The star charts....include all 173 stars used in the Almanac, together with a few others......" To use the others, their coordinates must be found from observation or in other sources, like the "Nautical Almanac and Ephemeris."

[@ryderpham5464]

What do the values of A, B, Z1, Z2, P, and H mean?

[@Billofthenorth1]

Anything with H has to do with the altitude of an object whether measured or calculated, Z has to do with Azimuths. The others I'm not sure of, probably component parts of the triangle. I have been looking for a reference on that so if you find one online I'd appreciate hearing about it.

[@jounihiltunen3729]

Hello, as you propably know, sight reduction solves a navigational triangle with GP of celestial object, Assumed Position and North|South pole as it points. Publication No 229 gives solution to entire triangle in one table, but its a bit hefty. Nautical Almanac Sight Reduction divides the triangle into two right angle triangles and solves each in turn. Thats why you go through tables twice. A and B are the perpendiculars of one half. A nd F are the perpendiculars of the other half. Slide no 9 in this presentation should clarify. All the best. www.stpaulsquadron.org/documents/Nav%202009%20Chapter%205%20NASR%20Reduce%20Plot.ppt

[@alphamale4609]

Why lower merpass time is given for moon but not for sun?

[@Billofthenorth1]

The explanation (doesn't give reason) is Sun Merpass is approximate GMT/UT when the sun crosses the prime meridian Moon upper is when the moon crosses the prime meridian Moon lower is when the moon crosses the 180 degree line of longitude From what I've read, it seems lower mer pass is of limited use, except in specific circumstances. They may have left it out for that reason

[@jasonpfeilsticker5692]

I am tryign to learn this stuff and I am using HO 229... there is no talk of A, F, or anything like that....

[@Billofthenorth1]

That's a different method with a different reference book. I've never learned it although I suppose I should.

[@markprange4386]

Use HO 214 or 249 instead.

[@marcg1686]

Use HO249, volume 1. The nicest of them all.

[@gabrielrosales8998]

Sir, why did you drew a LP on 249 degrees instead of drawing it on 241 degrees??

[@Billofthenorth1]

If you look at the origin point of the azimuth line you notice it is not the center of the compass rose.The line for azimuth of the sun is drawn 241 degrees from that point. The azimuth just happens to cross over the 249 mark but is not related to it. Look at the wide shot about 13:07.

[@gabrielrosales8998]

@@Billofthenorth1 Oooh I see I got 3 questions, 1) Why didn't you start on the center of the compass rose? 2) Why did u write 084 (W) Degrees on the top side and on the left side 43 (N) Degrees, is it always gonna be like that (North or South on the right side and West or East at the top)? and 3) How do you know where to plot the 2 points on the Plotting Sheet? (I apologize for my ignorance sir, this is something new to me).

[@markprange4386]

The American Nautical Almanac's sight reduction procedure is so ugly that almost no one ever gets it figured out. It is disregarded even more than the US "Sight Reduction Tables for Marine Navigation." "Sight Reduction Tables for Air Navigation" has been in favor since the 1950s. The earlier "Tables of Computed Altitude and Azimuth" are excellent--they just don't produce heights below 5°. The narrator of this video makes a valiant effort to demonstrate the Almanac's EZ Method, but what he has to work with would baffle Bowditch. Those who can't follow: don't give up. Just use the Almanac's daily pages, and its information about corrections for eye height, refraction, semidiameter, and parallax. I usually avoid tables that combine corrections.

[@eddieboykeliste8733]

Thank You

[@Wynds77]

Help me more please

[@Billofthenorth1]

poshwack Fragilito I just saw this reply. What do you need help with? Keep in mind I'm not a teacher or instructor.

[@ResearchFlatMoon]

looks like you are quite close to me

[@Billofthenorth1]

Michigan, north of Detroit an hour or so

[@ResearchFlatMoon]

@@Billofthenorth1 You are VERY close to me. We should have some coffee one of these days. You near Owosso? I'm doing some KZbin tutorials on sextants, wouldn't mind chatting about them.

[@mateusscarparo7152]

MY NAME IS MATEUS SCARPARO TOO

[@guil.meister4205]

hi sa mga student ni dean mg beaño.

[@abdulkkhan5095]

Great

[@Billofthenorth1]

Thanks, I hope it is helpful

[@mrjp1819]

Tu fast!

[@Chaxzify]

hi 5ece-1 HAHA 🤘

[@AJxxxxxxxx]

Fuck this is confusing 😩

[@Billofthenorth1]

I had to go step by step with the book by my side and repeat the procedure several times before I started getting it. The video is intended to help you along. And of course there is way too much material for me to explain everything and keep it short enough to be useful.

[@Billofthenorth1]

Learning how to do it, is harder than doing it.

[@AJxxxxxxxx]

@@Billofthenorth1 Thank you, you did a great job at explaining, it’s just I have an issue where when I’m starring at numbers It all starts to blend in together, I get the whole concept of intersect the circles on a map based on the angles of celestial bodies from you but I just start to fall apart once I see the numbers, I’m still trying though

[@Billofthenorth1]

@@AJxxxxxxxx Don't worry, you'll get it. You really only do adding and subtracting. I tried to make it so you don't need to know what you are doing or what its called. I figure once you start to grasp the basics you'll start to pick up on those things.

[@AJxxxxxxxx]

@@Billofthenorth1 Thank you

[@eddieboykeliste8733]

Thank You