Converting Star Chart Times For Your Locality
If you want to convert the above times for your locality in
- Find your longitude in degrees.
- Subtract 86 from your longitude (if you are east of 86
degrees longitude, you will get a negative number).
- Multiply the result by 4 giving the number of minutes
correction. (If east of 86 degrees the correction will be
- From the last value subtract one hour for each time
zone you are west of Eastern Time, or Add one hour for
every time zone you are east of Eastern Time.
- Add the result algebraically to the Grand Traverse
region time. That is the time for the chart in your
Here's an example: for Aberdeen South Dakota
- Longitude = 98
- 98 - 86 = 12 degrees
- 12 * 4 = 48 minutes
- Aberdeen is in the Central time zone. The correction
is -1 hour or -60 minutes. 48 - 60 = -12 (This is a
constant for this location)
- If the Grand Traverse region time is 9:00, then 9:00 -
0:12 = 8:48. The chart time for Aberdeen SD will be 8:48
Corrections for latitude aren't as easy. The standard
latitude for this chart is about 45 degrees. For latitudes
farther north the sky shifts to the south, for latitudes farther
south, the sky shifts to the north, revealing stars and
constellations invisible from the Grand Traverse region.
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