Experiments

Experiments:
North-South Meridian & Earth Latitude

"Jupiter and Saturn"

[Astronomy Home]
[1-Moon] [2-Planets]
[3-Eclipses] [4-Experiments]
[5-Galaxy & Constellations]
[6-Telescopes] [7-Stars]
[8-Observation] [9-Careers]
[FYI-For Your Information]

Mr. R.

REQUIREMENT #4 (part a): Using the shadow of a vertical pole in sunshine, lay out a true north-south line (a meridian)...

Find a flat open area that has sun in both morning and afternoon. Drive a 3-4' pole into the ground making sure it is VERTICAL. Tie a loop in the string and place it at the bottom of the pole.

Around 7-9 a.m. in the morning, place a small stick or stake in the ground exactly where the sun's shadow ends. Stretch the string and tie it to the small stick. Making sure the string is tight, drag a circle on the ground the radius of the string. Replace the stick and remove the string.

Watch the shadow of the sun during the day. It will slowly move around the pole. Does its shadow get shorter or longer?

Sometime in the afternoon or evening the sun's shadow length will come close to the circle again--watch carefully! As soon as it touches the circle mark it with another stick. You now have 2 short sticks across from each other. Draw a straight line between them ignoring the tall pole. This line points East and West. If you bisect this line (draw a perpendicular line at a 90-degree angle), you will have a North-South meridian line.

REQUIREMENT #4 (part b): ...then, using a line and the pole on another day, measure the altitude of the noontime sun and determine your latitude.

For this experiment, you will need a string and a protractor to measure angles (not angels). This MUST be performed at EXACTLY 1:00 PM during daylight saving time months (otherwise12:00 noon).

Measure the sun's altitude by the shadow it casts from the vertical pole. Tape or hold the string on top of the pole, making sure that your hand does NOT interfere with the sun's shadow. Pull the string tightly and place it exactly where the shadow ends.

Carefully place a protractor on the ground with its middle point exactly where the shadow and string meet. I find it helpful to enlarge a small protractor up to 8" x 10" on a copy machine. Now read the ANGLE (as accurately as possible) formed between the ground and the string. Write this angle down. If there are a number of scouts have them try it in groups. Come to an agreement on the correct angle.

Using the Sun Declination chart below, find where today's month and day intersect on the chart. This number is the declination angle. Write it down next to the angle formed by the sun. Now we get to do some math (don't worry--we just subtract and then add).

90 degrees
subtract the sun's altitude -___ degrees
(measured by protractor)

add the sun's declination +___ degrees
(as read from chart)

TOTAL = Your Latitude =___ degrees

NOTE: The winter days (and some spring and fall days) have NEGATIVE angles. Remember that when you subtract a negative number it is the same as adding!

Let's look at an example: I live in Ogden, Utah. Suppose the date is June 21st. We measure the sun's angle and find it to be about 72 degrees. We then look up June 21 in the chart and find an angle of 23.43 degrees. Now let's do the math:

                          1) Always start with 90 degrees                 90 degrees
                          2) Subtract the sun's altitude                   - 72      "
                                                   (measured by protractor)                                                    18      "
                          3) Add the sun's declination               + 23.43      "
                                                  (as read from declination chart)
                          4) TOTAL = Your Latitude               = 41.43 degrees

The actual latitude (as measured at the Ogden Airport) is 41º 12' (source)

SunDeclination by K. I. Malde/CV-Helios Network © 2001 (Used by permission)
Estimated in degrees from celestial equator for time 00:00 (UTC+1) DATE    JAN    FEB    MAR    APR    MAY    JUN    JUL    AUG    SEP    OCT    NOV    DEC DATE
01      -23,04 -17,46 -7,95    4,49    15,11    22,05 23,13 18,21    8,48   -3,24   -14,75 -21,89     01
02       -22,96 -17,18 -7,56    4,88    15,41    22,18 23,07 17,96    8,11   -3,65   -15,07 -22,03   02
03       -22,88 -16,89 -7,16    5,27    15,70    22,30 22,99 17,71    7,74   -4,05   -15,38 -22,17   03
04       -22,78 -16,60 -6,77    5,65    16,00    22,42 22,91 17,45    7,37   -4,45   -15,69 -22,30   04
05       -22,68 -16,31 -6,37    6,04    16,28    22,53 22,83 17,18    6,99   -4,85   -15,99 -22,42   05
06       -22,58 -16,01 -5,97    6,42    16,57    22,64 22,74 16,91    6,62   -5,25   -16,28 -22,54   06
07       -22,46 -15,70 -5,57    6,80    16,85    22,74 22,64 16,64    6,24   -5,65   -16,58 -22,64   07
08       -22,34 -15,40 -5,17    7,18    17,12    22,83 22,53 16,36    5,86   -6,05   -16,86 -22,75   08
09       -22,21 -15,08 -4,77    7,56    17,39    22,92 22,42 16,07    5,48   -6,44   -17,15 -22,84   09
10       -22,08 -14,76 -4,36    7,93    17,65    23,00 22,30 15,79    5,10   -6,84   -17,42 -22,93   10
11       -21,93 -14,44 -3,95    8,30    17,91    23,07 22,18 15,49    4,71   -7,23   -17,69 -23,01   11
12       -21,79 -14,11 -3,54    8,67    18,16    23,14 22,05 15,20    4,33   -7,62   -17,96 -23,08   12
13       -21,63 -13,78 -3,13    9,04    18,41    23,20 21,91 14,90    3,94   -8,00   -18,22 -23,15   13
14       -21,47 -13,44 -2,72    9,40    18,65    23,25 21,77 14,59    3,55   -8,39   -18,48 -23,21   14
15       -21,30 -13,10 -2,31    9,77    18,89    23,30 21,62 14,28    3,16   -8,77   -18,72 -23,26   15
16       -21,12 -12,76 -1,90 10,12    19,12    23,33 21,47 13,97    2,77   -9,15   -18,97 -23,31     16
17       -20,94 -12,41 -1,49 10,48    19,35    23,37 21,31 13,65    2,38   -9,52   -19,21 -23,35     17
18       -20,75 -12,05 -1,08 10,83    19,57    23,39 21,14 13,33    1,99   -9,90   -19,44 -23,38     18
19       -20,55 -11,70 -0,66 11,18    19,78    23,41 20,97 13,00    1,60 -10,27   -19,66 -23,40     19
20       -20,35 -11,34 -0,25 11,53    19,99    23,43 20,79 12,67    1,21 -10,63   -19,88 -23,42     20
21       -20,14 -10,97   0,16 11,87    20,20    23,43 20,61 12,34    0,81 -11,00   -20,10 -23,43     21
22       -19,93 -10,60   0,56 12,21    20,40    23,43 20,42 12,01    0,42 -11,36   -20,31 -23,43     22
23       -19,71 -10,23   0,95 12,55    20,59    23,43 20,22 11,67    0,03 -11,71   -20,51 -23,43     23
24       -19,48 -9,86     1,35 12,88    20,78    23,41 20,02 11,32   -0,38 -12,07   -20,70 -23,42     24
25       -19,25 -9,48     1,74 13,21    20,96    23,39 19,81 10,98   -0,79 -12,42   -20,89 -23,40     25
26       -19,01 -9,10     2,14 13,54    21,13    23,36 19,60 10,63   -1,20 -12,76   -21,07 -23,37     26
27       -18,77 -8,72     2,53 13,86    21,30    23,33 19,38 10,28   -1,61 -13,10   -21,25 -23,34     27
28       -18,52 -8,34     2,93 14,18    21,46    23,29 19,16    9,92   -2,02 -13,44   -21,42 -23,30    28
29       -18,26               3,32 14,49    21,62    23,24 18,93    9,57   -2,43   -13,78 -21,58 -23,25     29
30       -18,00               3,71 14,80    21,77    23,19 18,70    9,21   -2,83   -14,10 -21,74 -23,19     30
31       -17,73               4,10               21,91               18,46    8,84              -14,43               -23,13     31
DATE    JAN    FEB    MAR    APR    MAY    JUN    JUL    AUG    SEP    OCT    NOV    DEC DATE Created on the 29 september 2001 by K. I. Malde
CV-Helios Network © 2001 All rights reserved (Used by permission)

http://www.cv-helios.net/sundec01.html

HELPFUL LINK TO "SUN DECLINATION" INFORMATION
CV-Helios Network
The Analemma Great time photo of the sun during an entire year
The Sun's Yearly Motion (Quicktime video)

[Astronomy Home] [1-Moon] [2-Planets] [3-Eclipses] [4-Experiments] [5-Galaxy & Constellations]
[6-Telescopes] [7-Stars] [8-Observation] [9-Careers]
[FYI-For Your Information]

Animated graphics by Animation Factory

Webpage updated February 2003
Webmaster, Mr. R.