Here are a few simple formulas to determine Sunrise or Sunset time.

"Cos-1" means use the arc cosine key.
"Integral hour" means the single hour figure without minutes.  Example- "12"  not 12:14.

To make things easier first get the GHA of Sunrise using the following formula.  You can also simplify the process of getting the GHA by using HO-249, (with your AP. Latitude and the Sun's declination) finding the LHA for when Hc is closest to 0° and add your Ap. Longitude to it. 

For the declination figure just use the average declination for the day you want to calculate Sunrise.

360º – Cos-1( -Tan(Declination) x Tan(AP Latitude)) + Ap. Longitude = GHA of Sunrise

Look up the GHA in The Nautical Almanac and find the GHA integral hour figure lower than the calculated GHA figure found above.  Also obtain the GHA (in degrees) of the integral hour and the declination for the integral hour.

Use the figures in the following formula to get the time of sunrise-

GHA Integral Hour + (360 – Cos-1( -Tan(Declination) x Tan(Ap. Latitude)) + Ap. Longitude – GHA of Integral Hour) / 15

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Mercury will transit the Sun's disk on May 9 at GMT 11:12:00 and will exit 18:42:00

According to the USNO;

"The entire transit will be visible in eastern North America, northern South America, the Arctic, Greenland, extreme northwestern Africa, western Europe, and the Atlantic Ocean".

Click here for more information;

Mercury's Transit of the Sun's disk, May 9


...Fair weather & Clear Skies!

CelNav57

I've been reading some old Air Force manuals which mention using the Landfall procedure as a safe means to arrive at your destination while flying.

Francis Chichester used it (maybe invented it) and Fred Noonan did also (though for the latter it didn't work out too well).

Can anyone explain it to me as I'm rather confused in how to do it.

Paul

The following is from "Astronomical Phenomena for 2016" (USNO)
Get it here- Astronomical Phenomena for the year 2016

"A penumbral eclipse of the Moon, March 23. See map on page 75".

"The eclipse begins at 09h 37m and ends at 13h 57m".

"It is visible from Asia, Australia, Oceania, North America, western South America, Antarctica, the eastern Indian Ocean and the Pacific Ocean".

You can get the eclipse map here- Penumbral eclipse of the Moon- March 23
Go to page number 75


CelNav57

Would someone please explain to me what Co-Latitude is?

C. D.

Here's a question you may be interested in solving;

What is the date and time, in UT, of the 2016 vernal equinox?  

Solve it anyway you'd like- just get the correct answer to the closest second of time.

Hope to hear from you all.

CelNav57

The following is from The Astronomical Phenomena for 2016;

"A total eclipse of the Sun, March 8-9. See map on page 71. The eclipse begins at 23h 19m on March 8 and ends at 04h 35m on March 9".

"Maximum duration of totality is 04m 14s".

"It is visible from southern Asia, Oceania, Australia, extreme northwestern North America, the Indian Ocean, and the northern Pacific Ocean".

Here are more of the details-  Total Eclipse of the Sun, 2016 March 8

Go to page 71 for the map of the path.

CelNav57

Roald Amundsen wrote the account of his expedition of five Norwegians first to reach The South Pole on December 14, 1911.

The book is available for free here- The South Pole by Roald Amundsen

To describe the march to the Pole in a few words- it was brutal.  Five men in the fiercest part of the world, with no electronic communications relying upon DR and Sun sights to reach The South Pole!

Not to spoil the book for you; since they were in meta incognita, they had certain procedures to insure their survival and safe return to Framheim (their base in The Bay of Whales).

The book is very enjoyable reading and there are no discouraging words.

History presents too much of the Scott expedition.  It has been said that though Amundsen was the victor, Scott was the martyr.  Martyrs are remembered- victors are often forgotten.

I uploaded the 1911 Nautical Almanac which also contains the letter and English translation Amundsen had left at The South Pole, which Scott found, addressed to King Haakon VII of Norway.  Scott and his team perished on their return trip but the letter was found with him when he and his comrades were found a nine months later.

The 1911 Nautical Almanac on our site is dedicated to the greatest explorer of the 20th century- Roald Amundsen.

Celestial navigation is difficult for a multitude of reasons but I wish to focus upon one particular- the math portion.

Learning celnav was very difficult for me because my skill at math was and isn't very good and I'm not trying to improve it.  I don't drool over formulas or abstract ideas and principles.

The endless quantity of books and web sites that supposedly explain how to perform celnav were written by people* who don't appear to be able to explain it except to other mathematicians.  That's a pity as celnav really is a dying art for ocean navigation and it certainly should be encouraged as backup.

It seems to me that since those that are promoting astronav in print are either retired physicists, engineers or math teachers there is a loftiness and arrogance conveyed that is similar to the saying over Plato's Academy door- “Let no one ignorant of geometry enter here".   There is some doubt as to whether this was really there- my guess is it was- heck- the guy wrote "Republic"!

So it comes across as, "well, little man, unless you know the law of cosines we can't help you.  Black art, I think Francis Chichester called.

But, then there's job security- keep things vague and not really understandable and you'll have job security.

By the way- the Naval academy IS NOT going to teach celnav processes- just that the method exists and no more- no sight reduction or using a sextant.

No wonder everyone has a hard time with math! It's the teachers!

Keep in mind that the navigators in the past 150 years were mostly grade school to high school educated at best.  If they could do it- so can we!


* Do you really think I'm going to buy a book on celestial navigation written by someone named "Mary Blewitt"?! Blew it? are you kidding me?!

The following is copied from part of JeremyParker's post over at; [/url]
[url=https://thenauticalalmanac.com/Forum/showthread.php?tid=14]
Does anyone really shoot the Moon?


His question follows;

My follow up question perhaps belongs in a different thread - Who bothers with Noon sights, and why?

I ask because there seems to be an almost religious attachment to the noon sight amongst many navigators and a belief that it is necessary to determine latitude to obtain a fix! Consequently we hang around on deck for 20 minutes awaiting the magical zenith moment while our lunch is going cold in the galley below, only to have the only clouds of the day obscure the sun right about LAN. Why not snap off and reduce a quick series of sights whenever we please and cross the resultant LOP with that of our advanced morning sight. This still renders our position; we can still determine Lat and Long. We only NEED a Latitude if we are performing a Time Sight - an observation by which we determine LHA and thence Longitude - but when using the intercept method precise Lat is not necessary.