[AZ-Observing] Re: Vernal Equinox?
- From: "Brent A Archinal" <barchinal@xxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Mon, 25 Mar 2002 20:24:53 -0700
It's a good (and common) question. The difference is due to the Sun not
being a point source and due to atmospheric refraction, so some part of
the Sun is above the apparent horizon for several minutes more than 12
hours at the equinoxes. USNO has a more complete explanation posted at:
http://aa.usno.navy.mil/faq/docs/equinoxes.html . Very useful answers to
similar astronomical questions are posted at the link one step higher,
i.e.: http://aa.usno.navy.mil/faq/ .
- Brent Archinal
RGP14159@xxxxxxx
Sent by: az-observing-bounce@xxxxxxxxxxxxx
03/25/2002 08:04 PM
Please respond to az-observing
To: az-observing@xxxxxxxxxxxxx
cc:
Subject: [AZ-Observing] Vernal Equinox?
March 20 is when the Vernal Equinox happens, and the sun rises due East
and
sets due West.
I also see that for the Phoenix area, the day that was exactly 12 hours
long
was March 16, when the sun rose at 6:35 am and set at 6:35 pm (according
to
the newspaper and my palm-pilot).
What I am not understanding is why these days don't coincide? I have
looked
at all my reference materials, and have checked out a number of web sites,
but can't find an answer. Is this too easy a question to dignify with an
answer, or is this a question that anyone can help me with? Does it have
to
do with our latitude, or the equation of time, or what?
Randy Peterson
EVAC
--
This message is from the AZ-Observing mailing list. See this message's
header if you want info about unsubscribing or the list's archive.
This is a discussion list. Please send personal inquiries directly to
the message author. In other words, do not use "reply" for personal
messages. Thanks.
--
This message is from the AZ-Observing mailing list. See this message's
header if you want info about unsubscribing or the list's archive.
This is a discussion list. Please send personal inquiries directly to
the message author. In other words, do not use "reply" for personal
messages. Thanks.
Other related posts:
