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View Full Version : How is sunrise determined?


Tricky1549
Apr 6, 2008, 05:52 AM
How is sunrise determined for a particular place? I mean if they say sunrise is at 6:30 AM at NYC where is it first seen? Thanks

Stratmando
Apr 6, 2008, 06:20 AM
In NYC, it is first seen from the highest elevations(Mountains)or a tall building. The ground people will have to wait. Are you talking sunrise for avaition?

Capuchin
Apr 6, 2008, 06:26 AM
Sunrise is the time at which the first part of the Sun appears above the horizon

Credendovidis
Apr 6, 2008, 08:54 AM
See Capuchin's reply.
But the higher and the more eastern you are located, the earlier you can see it. Logical of course, standing on a rotating sphere, waiting to see what appears from below the horizon...
.
And sunrise is always seen in an eastern direction, with the north-south direction changing accordingly to the seasons.

As to what causes the seasons : HAVE A LOOK HERE ! (http://www.crh.noaa.gov/fsd/astro/season.php)

:)

Tricky1549
Apr 6, 2008, 01:21 PM
In NYC, it is first seen from the highest elevations(Mountains)or a tall building. The ground people will have to wait. Are you talking sunrise for avaition?

NO, just where do you have to be to see the sunrise in NYC, sans the mountains and high buildings Thanks

Stratmando
Apr 6, 2008, 06:25 PM
You could be probably be anywhere in New York, I would get up 10 minutes early and not miss it.

Credendovidis
Apr 6, 2008, 06:28 PM
NO, just where do you have to be to see the sunrise in NYC, sans the mountains and high buildings Thanks
As eastern as possible.
:)

Capuchin
Apr 7, 2008, 04:13 AM
In NYC, it is first seen from the highest elevations(Mountains)or a tall building. The ground people will have to wait. Are you talking sunrise for avaition?

NO, just where do you have to be to see the sunrise in NYC, sans the mountains and high buildings Thanks

They probably measure it at the same point that the people who make the road signs pointing to NYC measure it to :rolleyes:

Credendovidis
Apr 7, 2008, 07:44 AM
They probably measure it at the same point that the people who make the road signs pointing to NYC measure it to
That may be true. But the only correct answer to Ricky's questions
- "just where do you have to be to see the sunrise in NYC, sans the mountains and high buildings"
and
- "I mean if they say sunrise is at 6:30 AM at NYC where is it first seen?"
Is :
As eastern as possible.That is where at street level you see the sunrise FIRST!

:rolleyes:

ebaines
Apr 7, 2008, 09:48 AM
When "they" say that sunrise in NYC is at 6:30 AM they are referring to a standard set of tables that list sunrise times based on the data and your longitude and latitude - for NYC it's probably based on a location like Central Park. It's basically an idealized calculation that assumes a clear horizon for an observer at sea level. Obviously if you are in a tall building you see the sun before those at street level. And if you are in a tall building at the eastern edge of the city limits you'll see it before anyone else in the city. Assuming that NYC is approximately 10 miles wide east-to-west, all else being equal an observer at the eastern border should see sunrise approximately 30 seconds before an observer at the western edge (if they are both at the same height above sea level). And for every 100 feet in altitude your sunrise is about 13 seconds earlier.

Credendovidis
Apr 7, 2008, 03:20 PM
... All else being equal an observer at the eastern border should see sunrise approximately 30 seconds before an observer at the western edge ...
Indeed : this agrees with BOTH of Ricky's questions!
- "just where do you have to be to see the sunrise in NYC, SANS the mountains and high buildings"
and
- "I mean if they say sunrise ... where is it FIRST seen?"

:rolleyes:

Tricky1549
Nov 16, 2009, 07:53 PM
That's exactly what I wanted to know. Thanks

Tricky1549
Nov 16, 2009, 07:56 PM
That's exactly what I wanted to know. Thanks ebaines