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GeoAstro Applets |
Astronomy |
Chaos Game |
Java |
Miscel- laneous |
What you need:
The sundial is
using a CD case (for 4 discs). You will need to print
and glue the hour scale to a CD disc (or use a
printable disc) and to mount a gnomon in the center
casting a shadow to read the current time. shim(s), 4 mm
socket, 4 mm banana
plug, 1.5-2.0 mm
rod (gnomon).
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The socket, plug, and gnomon at the center. | Aligning the disc (by a bubble level), and the gnomon. |
To
change the input of the latitude and longitude text
fields click into the applet area within the red frame first ! |
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enter your longitude in decimal
degrees, then press the button "Apply input". |
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Date, Month, Year |
Select the
date, month, and year from the menus. |
Hours | Time is
Standard Time without daylight saving time, referring to the data in blue only, not relevant for drawing the disk. |
Press the button
"DRAW DISC":
The hours on
the time scale are "Local Apparent Time (LAT)" or
true solar time, the shadow pointing True North at
12:00. It may differ considerably from Standard
Time (ST) of the time zone.
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You may also
print a disc showing Standard
Time (ST). The conversion
from Local Apparent Time to Standard Time is done by
the applet choosing "Standard Time" from the menu. Choose
"Standard Time":
Standard Time is computed from Local Apparent Time (LAT) taking into account the longitude of own position, the longitude of the Standard Time, and the equation of time (EQT), . The correction (D) for longitude is +4 minutes per degree of longitude East of Standard Time, or -4 minutes per degree of longitude West of Standard Time, plus the equation of time (EQT): LAT = ST + D + EQT Example: For a location at 10° E the longitude of Standard Time is 15° E, thus D=5*(-4min)=-20min. On Mar 03 the equation of time is EQT=-12min. At Local Apparent Time 15:00, the Standard Time is: ST= 15:00 + 00:20 + 00:12 = 15:32 The equation of time varies between about -14 minutes on February 11 and +16 minutes on November 3. Accepting an error of +/- 2 minutes for the Equation of Time seven dates are sufficient to approximate the curve: Print
out 7 discs for the following dates:
No
1: Jan 09
No 2: Jan 20 No 3: Apr 04 No 4: Apr 20 No 5: Sep 16 No 6: Sep 27 No 7: Oct 10 Find
the date within the first column of the
table which is nearest to the current date
to get the number of the disc to be used.
Example: For Mar 15 to Mar 28 use disc no. 1 (Jan 09). Print
out the cover and the Equation of Time
diagram, format 13.7 cm x 11.8 cm each, by
this .doc file:
Table
of altitude, azimuth, and local hour angle
are also available, listed by LAT (Local
Apparent Time) or Standard Time. Select
from the menu "Write Table...":
Press the button "Azimuth Graph": Details about the azimuth angle of the Sun Download Demo (ZIP) To expand the file use 7-Zip, Winzip, etc. |