Calculating sunrise and sunset between two points

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bawn79 B
bawn79 Dec 4, 2008 14:18:38
Replying to tiompan

tiompan wrote:
UncleRob wrote:
Hi Bawn
Good question!
I bookmarked this page to come back to a while ago, I have to say I haven't tried it yet myself...
http://www.geomancy.org/astronomy/sunfinder/calculator/index.html

See what you think.

Rob

Hi Rob , One problem that you might get with the site is working out the elevation .If you can do that then it looks like it will provide quite good accuracy .
Ive always wondered how elevation affects this, I know mountains etc may be in the way but generally you can observe this at the site.
Is that the main problem or is there something Im not thinking of?

T tiompan
tiompan Dec 4, 2008 14:30:23
Replying to bawn79

bawn79 wrote:
tiompan wrote:
UncleRob wrote:
Hi Bawn
Good question!
I bookmarked this page to come back to a while ago, I have to say I haven't tried it yet myself...
http://www.geomancy.org/astronomy/sunfinder/calculator/index.html

See what you think.

Rob

Hi Rob , One problem that you might get with the site is working out the elevation .If you can do that then it looks like it will provide quite good accuracy .
Ive always wondered how elevation affects this, I know mountains etc may be in the way but generally you can observe this at the site.
Is that the main problem or is there something Im not thinking of?
The simplest way to show the effect of elevation is to imagine that you are attempting to observe an equinox sunrise i.e. due east , but if you there is a 30 m high wall between you and the sun then you will not see the sun until it has moved further west and subsequently higher on the horizon .The higher the wall the later the sunrise and more westerly the bearing . You only experience an equinox sunrise at approx 90 degrees if the horizon is relatively flat .

T tiompan
tiompan Dec 4, 2008 14:33:13
Replying to bawn79

bawn79 wrote:
tiompan wrote:
UncleRob wrote:
Hi Bawn
Good question!
I bookmarked this page to come back to a while ago, I have to say I haven't tried it yet myself...
http://www.geomancy.org/astronomy/sunfinder/calculator/index.html

See what you think.

Rob

Hi Rob , One problem that you might get with the site is working out the elevation .If you can do that then it looks like it will provide quite good accuracy .
Ive always wondered how elevation affects this, I know mountains etc may be in the way but generally you can observe this at the site.
Is that the main problem or is there something Im not thinking of?
The simplest way to show the effect of elevation is to imagine that you are attempting to observe an equinox sunrise i.e. due east , but if you there is a 30 m high wall between you and the sun then you will not see the sun until it has moved further west and subsequently higher on the horizon .The higher the wall the later the sunrise and more westerly the bearing . You only experience an equinox sunrise at approx 90 degrees if the horizon is relatively flat . The same problem applies to all astro events . Hope that helps and is not too convoluted .