I only recently discovered the sun doesn't always rise in the east and set in the west. I'm nearing 40 and I only just discovered this. So now I understand that the sun rises on June 21st (northern hemisphere) quite a bit north of east and sets quite a bit north of west, hence why we get the longest day. Then the reverse is true for December 21st.
SO MY QUESTION IS: HOW MUCH DOES THE SUN'S ANGLE CHANGE THROUGHOUT THE YEAR FOR A GIVEN PERIOD OF TIME?

If I could work out that on say June the 21st the sun rose at 80 degrees and set at 280 degrees and on July 21st it rose at 85 degrees and set at 275 degrees I could say that for each month there was a 5 degree change in angle at sunrise and a 5 degree change at sunset.

I realise it must be less than this but I'm using this as an example.

I'm also aware that one has to remember you can't just point a compass and say 'yep it's going to come up at 93 degrees today' because you have to take into account the declination for that time of year and that area on the planet.

If I used a hand bearing compass I could stand on an open field and gaze through my compass and providing I've either added or subtracted for my declination then worked out the angle the sun should rise for that month I should be able to pinpoint the exact spot the sun should rise - providing I'm looking at sea level.

I have found various websites like the Photographers Ephemeris which plot the sunrise/set on a Google map but Google does not yet offer the sort of detail necessary to provide enough clarity world wide.

Can anyone help with my question, I'd very much appreciate their help.

If my memory serves, the daily change isn't constant -- it describes a curve, with the daily change getting smaller as it approaches each end (summer and winter solstice.)

The US Naval Observatory publishes data on sunrise and sunset. Try this page for more info than you could possibly want <grin>.

If you have a handheld device, you can get an application that will determine various sun/moon data. I use Focalware for my iPod Touch, though it works better on an iPhone with the built in GPS.

Now that you have discovered this fact, you'll find it to be very useful for landscape and architectural photography. For example, my campus has several buildings that face mostly north. I can figure out what sort of light I want on the front, then what week I need to shoot to get that light.

The Wolfram Alpha Computational Engine should be able to compute this - but I don't really know how.
For example if you search for sunrise 21st june london you'll get the time of sunrise in London at the given date.

I'm sure it should know the angle of sunrise, too, but I don't know what to search for "sunrise latitude" gives something, no idea if it's useful.
But maybe you could ask the wolfram staff how to compute this, because this question should be right in alphas ballpark.

You can do this easily with astronomy software (e.g. SkyMap Pro, the Sky ,etc.) for any date, time, location. The examples I listed you would have to buy but you should be able to find freeware on the web - Google "astronomy freeware" and you should be able to locate something that could help.

Also, in case you did not know Google Earth (from at least ver. 4) lets you view sun shadows on the ground throughout the day and based on topographic relief - that may be helpful as a rough guide if you are trying to determine if surnrise/sunset sun is or is not going to strike a feature of interest to you. But I do not know if it allows you to pick the date or not as I never thought to try.

Andrew

I use a piece of hardware known as the Dubois Sun Position Compass:

Click to view attachment

Web site (probably one of many similar sites): http://www.ephotozine.com/shop/product564.html

I am not affiliated with them, just a user.

Thank you all for your help and time to answer my question. I didn't realise there would be a greater angle one month to the next. Google earth is a good idea but it won't allow me enough precision. For instance if I'm say in a small canyon and I want to know when the sun might set along it's length but Google earth doesn't show the canyon because it's not at a major city and therefore has lesser detail.

Right now I'm sitting in my truck in a motel car park but when I have more time I'll check out some of the websites mentioned.

Thank you.

Most of these sun/moon calculators mentioned above (and others) can work off long/lat coordinates, so all you need is to find a topo map/software that's detailed enough to get the coordinates for the location you're interested in.

It'd be nice if Garmin put more detailed sun/moon data in their hand-held GPS units...

Is there a good iPhone app that will do a good job of this? If so, can someone give me the name?

Thanks

Del

Read post #2 again, note "Focalware." It works well on my iTouch, but will be better on an iPhone.