Help! A photographer emailed me yesterday to say that this week the sun will set behind a particular landmark in San Francisco, but he didn't (won't) say how he figured it out.

How does one do that, and where can I go (online?) to learn that? For example, I'd like to know when the moon will rise over the peak of Mt. Diablo in California and where I'd have to be to photograph it. Also, when does the sun set between the two towers of the Golden Gate Bridge in San Francisco, and where I'd have to be to photograph it. You get the idea.

Anyone know how to do the calculations and where I can go to learn it?

Thanks very much!!

Gary
web.mac.com/misterellis

i'm pretty sure you can do it pretty easily using google earth. i'll get back to you on that approach.

I use ephemeris by Jonathan Sachs http://home.comcast.net/~jsachs34/#Ephemeris%201.0 there's a desktop version as well as a windows mobile version.

There's also a website, here: http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html that will give you what you want to know...

Mike.

It's a good idea to buy a cheap handheld GPS device. These devices will give you sun/moon information very easily!

Luis

Another option is to go to http://www.wunderground.com , enter the city to get the weather forecast, then scroll down to Astronomy, click on Extended View, and look at Azimuth for the compass direction for the sunrise and sunset.

- Greg

www.GregVaughn.com

Brilliant help, all of you! Thanks very much!

Gary

Check out Planetarium, a program for Palm hand-held computers. Search for Michael's review on this site. It graphically shows you sunrise/sunset time and direction, moonrise/moonset and lunar phase for any place on earth. Just type in Lat./Long. and time/date and you're all set. I find it invaluable, and you can carry the whole thing in your pocket.

I find this link most useful:
http://www.timeanddate.com/
It calculates time and azimuth (i.e. compass direction) of sunrise/sunset and moon rise/set for any town worldwide for an entire month. If you fiddle a bit with the print settings, the table fits on a single page.

The NOAA site listed above, as far as I know, calculates the position of the sun/moon on the sky in hourly or so intervals for a day. Maybe useful if you want the sun/moon in a specific spot on the sky. Otherwise, the sun/moon rise calendar may be more useful.

I just downloaded an iPhone app called Focalware to my iPod Touch. It tells you the azimuth and elevation of the sun and moon for any location at any time. It's easy to use and seems pretty stable, and only cost $10. (Plus the cost of the iPod of course.) It works better with the iPhone with the built-in GPS system, but you can easily use it with the iTouch if you can enter the GPS coordinates of your location (or if you have wifi access it can figure out your location by itself.)

So I can figure out when and where the sun/moon will rise tomorrow, which is useful. More useful, though, I can figure out what day and time in the future the sun/moon will be exactly where I need it for a specific photo effect (like your friend and the SF landmark.)

What about for figuring out extremely precise moon or sun trajectories, for example?

Say you had a tiny rock arch, and you wanted to shoot a night timelapse of the moon passing through the tiny arch, hours and hours from when you set the camera up and started it. Is there any device that precise? It would be like threading a needle.

Well, Ephemeris mentioned above, will print you out a chart of the sun or moon altitude and azimuth at 15 minute intervals for any location or time. I would have thought an accurate compass and sextant would then give you a precise camera placement. If you are also moving the camera, you may want to place the 3 variables on a single graph for simplicity's sake. Cheers, David

Going further, is it possible to get a graphic representation of the lighting on a picture of a scene or building, given the position of the sun and time of day/year? Something like a lighting diagram? With many digital cameras now having GPS capabilities, one could take a picture, and using this data, overlay this simulation to see when the scene/building would be lit in the desired way, weather permitting.

Kumar

The above mentioned programs for hand held devices are relatively low precision. The US Naval Observatory publishes in interactive almanac that can give more precise data for the sun, moon, planets, and major stars.

http://www.willbell.com/almanacs/almanac_mica.htm

Bill

All good suggestions. I found the U.S. Naval Observatory data site to be very useful as well: USNO Data.

A free sunrise and sunset dashboard widget for Mac OS user: http://captaindan.org/sw/Sol/

If you wanted extreme precision, you'd have to know the azimuth between your subject and your camera location very accurately. Since you'd be trying to predict movements of the sun or moon, that azimuth would have to be what is known in the precise positioning business as an astronomic azimuth. If you used a compass or simple transit to determine a magnetic azimuth, you'd then have to convert that to something relative to true north by knowing a precise magnetic declination for the area. So predicting the azimuth of the sun or moon, and the time of rise/set, would only be part of your problem.

If you want best obtainable precision, then you'll need to make all the measurements with a theodolite, and take into account the influence of the local gravity field on your theodolite's orientation to the local level plane. That's absolutely necessary for scientific work. Not so much for shooting nice photos.

Not sure if you own an iphone but there is a really nice app that I downloaded the other day what will show you where the sun and moon will be on a given day. It called Focalware and with some dragging of the sun / moon, indicates the elevation at various points in the day.