The nautical almanac

You may not like it Gentlemen BUT!! Familiarity with the Nautical Almanac and it’s contents is absolutely ESSENTIAL! Is to introduce you to the Nautical Almanac, It’s layout It’s contents and of course, How to use it At the end of this lesson you will :Know the principle contents of the Nautical Almanac Be able to demonstrate how to obtain GHA & Declination of Celestial Bodies Be aware of the necessity to be precise when entering the tables in the Nautical Almanac Be able to apply the “d” & “v” corrections correctly The Nautical Almanac contains the GHA, tabulated for every hour of GMT for the Sun, Moon, Planets and Aries for the entire year Extreme care MUST be taken, both in daily pages and Increments Tables to USE THE CORRECT DAY AND COLUMN A) The Sun B) Aries C) Jupiter A) 3000 38.4’ B) 3360 35.9’ C) 2930 15.9’ Date: April 28th 2000 Time:- 0800 UTC Use of the Nautical Almanac The Increments Tables (aka The Yellow Pages) contain the corrections to be added to GHA for minutes & seconds of time For example:The Date is 10th September 2000 The time is 09h 23m 11s GMT Find the GHA of the Sun: GHA (0900): 3150 46.9’ Increment( 23’ 11”) 50 47.8’ GHA= 3210 34.7’ The GHA of a Star is found by taking the GHA of Aries and adding to this the SHA of the Star The SHA and Declination of 57 Stars are tabulated in the daily pages in alphabetical order and a complete list of 173 stars can be found at the back of the Nautical Almanac (See Page 268) The Declination of the Sun, Moon and Planets is tabulated for every hour of GMT WHY IS THERE NO DECLINATION FOR ARIES? Declination of Sun, Moon & Planets • To interpolate for minutes of time the “d” correction is used The “d” is the hourly rate of change of Declination i.e how much “d” changes in one hour However, we generally need to correct for minutes of an hour To this, the “d” number at the bottom of the appropriate column on the daily pages is taken, and the correction is found by entering the appropriate minutes column in the Increments Tables with this “d” number, as follows:Find the Declination of the Sun for 06h 12m 20s Click 2nd time round Now that we have our correction, how we apply it…??? Find the Declination of the Sun given:Date: 23rd July 2000 Time: 1553 GMT • Dec’l (1500) • “d”(0.5) • Dec’l = N 190 55.5’ = 0.4’ = N 190 55.1’ Finding the “d” correction to apply for the Planets • This is done in exactly the same way as for the Sun… • As can be seen from the following:- Aries & the Stars • Aries is a fixed point on the equinoctial as we have already seen, therefore it does not have a Declination and consequently no “d” correction • The Stars are also essentially fixed points on the Celestial Sphere, either North or South of the Equinoctial and therefore their Declination does not change greatly over long periods • Reference to the Nautical Almanac daily pages can be made to confirm this The “v” Correction • This correction is applied to the Planets only • It is applied to the GHA of the planet at the same time as the Increment (for minutes & seconds of time) • The “v” correction is to be added, except in the case of Venus when the “v” correction is prefixed by a minus (-) sign • The “v” correction is obtained in the same way as the “d” correction, by entering the Increments Tables at the appropriate ‘minutes’ page [...]... and therefore their Declination does not change greatly over long periods • Reference to the Nautical Almanac daily pages can be made to confirm this The “v” Correction • This correction is applied to the Planets only • It is applied to the GHA of the planet at the same time as the Increment (for minutes & seconds of time) • The “v” correction is to be added, except in the case of Venus when the “v”... Finding the “d” correction to apply for the Planets • This is done in exactly the same way as for the Sun… • As can be seen from the following:- Aries & the Stars • Aries is a fixed point on the equinoctial as we have already seen, therefore it does not have a Declination and consequently no “d” correction • The Stars are also essentially fixed points on the Celestial Sphere, either North or South of the. .. example :The Date is 10th September 2000 The time is 09h 23m 11s GMT Find the GHA of the Sun: GHA (0900): 3150 46.9’ Increment( 23’ 11”) 50 47.8’ GHA= 3210 34.7’ The GHA of a Star is found by taking the GHA of Aries and adding to this the SHA of the Star The SHA and Declination of 57 Stars are tabulated in the daily pages in alphabetical order and a complete list of 173 stars can be found at the back of the. .. an hour To do this, the “d” number at the bottom of the appropriate column on the daily pages is taken, and the correction is found by entering the appropriate minutes column in the Increments Tables with this “d” number, as follows:Find the Declination of the Sun for 06h 12m 20s Click 2nd time round Now that we have our correction, how do we apply it…??? Find the Declination of the Sun given:Date:... order and a complete list of 173 stars can be found at the back of the Nautical Almanac (See Page 268) The Declination of the Sun, Moon and Planets is tabulated for every hour of GMT WHY IS THERE NO DECLINATION FOR ARIES? Declination of Sun, Moon & Planets • To interpolate for minutes of time the “d” correction is used The “d” is the hourly rate of change of Declination i.e how much “d” changes in... minutes & seconds of time) • The “v” correction is to be added, except in the case of Venus when the “v” correction is prefixed by a minus (-) sign • The “v” correction is obtained in the same way as the “d” correction, by entering the Increments Tables at the appropriate ‘minutes’ page