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    Re: Using Table 4 HO249 for Suns GHA and Dec.
    From: Samuel L
    Date: 2015 Mar 12, 13:58 -0700

    I use it quite a bit.

    Maybe an example would help answer your question?

    Working with the following date and time;

    March 12, 2015

    GMT= 20:15:21

    First let's determine GHA;

    1- Find the year in "table a". Next to 2015 you'll see a +1. That means add 1 hour to the GMT you're working with for the year 2015. In the example's case that means GMT 20 + 1= 21 GMT.  Rememember or write down "21".

    2- Locate the Month ("Mar") in the big table above table a.

    3- Find the day number in the left hand column labled "d" which is headed at "OT 00h". In this example it would be "12".

    4- Move across the "12" line to find in the "Mar" "E" column the numbers 2 30 (which means 2° 30')

    5- Locate the number just below 2° 30' and find 2 34 (which means 2° 34'). For the use of Table 4 you must use the figure in the next day number to determine what I call the "offset".

    6- Notice that the difference between 2 30 and 2 34 is 4 minutes or arc and that the "E" figure is increasing. In this example
          I would write down +4.

    7- Get the GMT number you determined in step 1 above which is 21.

    8- Here's how I arrange those numbers; +4/21. You need those numbers for table b.

    9- In "table b" locate in the "Diff." column the number 4.

    10- In "h" column drop down to find the number 21.

    11- Where the 4 column and the 21 (h in bold) intersect you'll see the number 4.

    12- Add the 4 to the figure you obtained in step 4 from the "E" column 2 30. The answer is 2 34.
                   Write figure down. You'll need it later in step 17.

    13- Now get the real hour and minute figure you're using which is 20:15.

    14- In table c locate 20 in the "h" column.

    15- Find the 10m column at the top of table c (we'll deal with the remaing 5 minutes and seconds in step 18)

    16- Where the 20 and 10 intersect you'll find the number 117 30 which means 117° 30'

    17- Add the 117° 30' to 2° 34' to get 120° 04'

    18- In table d find 05 in the "m" column and 21 in the "s" column (it's the 4th column from the left side of table d).

    19- Next to the 21 in the "s" column you'll see 1 21 slightly down to the right of it in the ° and ' columns.

    20- Add the figure you found in step 19 (1° 21') to the figure you determined in step 17 (120° 04') to get 121° 25'.

    21- The Sun's GHA for the date and time in this example is 121° 25'.

    Declination is done in the same way EXCEPT you go no further than table b.

    'Hope that helps.

    Sam L.

     

     

     

       
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