# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**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 t**able b**.

'Hope that helps.

Sam L.