How To Calculate Sunrise using a Nautical Almanac!

[@varunthipireddy1074]

very nicely explained sir...please make more videos on the use of nautical almanac

[@sarabjitsingh5766]

Very nicely explained,,,,,,thank you sir

[@oleksandrkolisnyk1341]

The LMT are strictly for January 14 (middle date on page) and 0◦ longitude; for more precise times it is necessary to interpolate, but rounding errors may accumulate to about 2m. (a) to January 13d − 75◦/360◦ = Jan. 12d.8, i.e. 1 3 (1·2) = 0·4 backwards towards the data for the same latitude interpolated similarly from page 17; the corrections are −3m to nautical twilight, −2m to civil twilight and −2m to sunrise. Could you be so kind to explain this interpolation. Thank you

[@resdamaulana8898]

Sir , why longitude in to time divide by 15?

[@AlistairBaillie]

Hi - the earth rotates 15 degrees of longitude every hour, so to convert from longitude to a time difference we divide by 15 (and to convert the other way we multiple the time difference (in hours) by 15 to get longitude)

[@Stefan.rogers]

Show how to interpolate to find the time and not just say the answer please

[@mr.minimal6466]

nicely explained

[@AlistairBaillie]

Thank you 😃

[@haiminh5469]

Can you explain why we subtract east and add west?

[@AlistairBaillie]

The times given in the almanac are in reference to Greenwich (the zero degree line of longitude) in the UK. If you are east of Greenwich the event will occur earlier thus you subtract. If you are west of Greenwich the event will occur later thus you add.

[@haiminh5469]

@@AlistairBaillie thanks you sir

[@vladimiriatsenko2374]

Awesome! Thank you!

[@AlistairBaillie]

You're welcome!

[@ongkisuprian784]

If you don't mind, cuold you explain the procedures how to use sextant to fixing position ?

[@markprange238]

St Hillaire Method: A celestial body's computed height (e.g. 60° 10') is subtracted from the observed height (e.g. 60° 50'). The difference in (e.g. 40') arcminutes is about how many (e.g. 40 NM) nautical miles off (in the direction of the body) the line of position is. Plot that line perpendicular to the (calculated or tabulated) azimuth of the body. Do the same with a body which is in a different direction. [The St Hillaire Method is also useful in locating a sunrise Line of Position. This is very useful for quickly finding the time of sunrise at a known position. The difference between observed height and an assumed position's computed height tells where to plot the sunrise LOP. How far east that LOP is gives an excellent idea of how many seconds (4 per arcminute of the diff. in longitude) to add to the assumed time].

[@AlistairBaillie]

Hi +Ongki Suprian, i've covered this in a different video in the series - kzbin.info/www/bejne/paq2daiDm5dmZsU

[@jayaratnam44]

I want sunrise and sunset timings for February at Coimbatore

[@myname-dq5sw]

Do you a formula for that?

[@markprange238]

my name: The Spherical Law of Cosines.

[@markprange2430]

Yes. The Nautical Almanac Office calculates the instant to the fraction of a second, and rounds to the nearest minute. The formula for computed height (Hc) is used. That is the Spherical Cosine Law written in navigational terms. It is written as observed height (Ho), though-applying the corrections for dip (about -.97 × the square root of the eye height in feet), astronomical refraction (about -33.7 arcminutes, terrestrial refraction (about -.18 arcminutes × the square root of eye height in feet), semidiameter(about -16 arcminutes), and parallax in altitude (about +.144 arcminute). (Hs ≡ 0° 00.0'. So the Ho is, in effect, the sum of the corrections.) Use your best estimate of the Sun's declination. Then the equation is rearranged algebraically to isolate and solve for the meridian (Δ longitude) angle ("t") or the LHA. From t & the longitude of the observer the GHA (West longitude) of the Sun is found arithmetically. Voila! In the Nautical Almanac, the corresponding instant of sunrise is interpolated.

[@opeyemiojutiku1264]

What are the real life applications of time of rise, set and twilight at sea?......in school, we solved this problems....but for example in calculating amplitude, you only need to observe when the sun is at SD and make observation. No need to calculate time of rise like we would do in class.... Anticipating your response . Thanks, I appreciate your videos

[@brightawe9002]

To determine location at sea

[@itsmemarkyyy8846]

When you have an operation early morning and the management plans to go early as sunrise, then you can apply it