Posted by Mike on .
Equation of Time.
I have read 2 explanations of the Equation of Time which seem to contradict each other.
Today the Equation of Time is 16 minutes 15 seconds.
I have seen it expressed as 16.15 F. The F means FAST meaning the sun is 16m 15s FAST.
Another explanation advised me to add the 16m 15s to GMT (UTC) before commencing my calculations which incidentally are to establish LONGITUDE using LAN.
Can anyone offer a clearer explanation please.
Both are the same. You want for longitude the difference between UT and local time. Local time is determined by a clock, minus the EOT. That is, if the sun is running fast, subtract it from local time. Since you are determing the difference between Local time and UT, adding it to UT is the same.
Longitudetime=Localtime - UT
But if you are observing a sun event, such as meridian, you correct for EOT.
longitudetime= localtime - EOT -UT
or as above
longitudetime= localtime - (UT + EOT)