Position of the sun, direction of shadows

Discussion in 'Large Format' started by leonard_evens, Jul 4, 2003.

  1. Where can I find information about the position of the sun in the sky
    as a function of latitude, date, and time of day? I tried a search on
    "altitude and azimuth", but it referred me to a previous posting that
    I was denied access to for some reason. There was also a reference to
    a US Navy site, but I was also denied access to that. I hope I don't
    have to write my own program to derive the appropriate information. I
    did find some reference to Palm Pilot programs, but I don't have such
    a PDA, and I would rather not have to carry one with me in the field
    anyway.

    I understand generally about the path the sun takes in the sky, but I
    am having a little trouble visualizing it three dimensionally. Can
    anyone recommend a reference for a refresher course on such matters?
     
  2. See Gallileo
     
  3. Try looking at a nautical almanac. It will have the altitude and azimith of the sun listed on a minute by minute basis. You need to know your location (latitude) and the time. They are relatively inexpensive but are date specific so you need a new one every year.
     
  4. http://aa.usno.navy.mil/data/docs/AltAz.html

    Try this site. The computed tables give the azimuth and altitude in 10 minute intervals. Negative numbers in the altitude indicate that the sun is below the horizon.
     
  5. Leanord, I did a quick Google search for "navigation tables" and found this:

    National Imagery and Mapping Agency (NIMA) Maritime Safety Information Division http://pollux.nss.nima.mil/index/index.html

    I didn't delve into the site at all but it may get you the information you need for altitude and azimuth of the sun at a specific location.

    The standard reference used by the US Navy to explain all this is "American Practical Navigator (Bowditch)". Here's another link that has some of the typical stuff used in celestial calculations and also offers Bowditch for sale.

    http://www.waypoints.com/celestialsupplies.html

    Calculating sunrise and sunset times by hand is not too difficult. Both the US Navy and Royal Navy publish tables each year to do this. The Local Apparent Noon, the time of day when the sun is at its highest, follows from sunrise and sunset.

    The azimuth angle is a bit more difficult and time consuming. Believe me, being able to get this info from the 'net or a computer program is MUCH easier than doing it by hand from the tables. Have fun and good luck!
     
  6. Hi Leonard –

    The Naval Observatory publications are helpful if you’re an astronomer, but might be confusing otherwise. If the basic movement of the sun confuses you, then tables of coordinates might not be quite the ticket.

    I assume you’re in the Northern Hemisphere. If you face south, the sun will rise on your left and set on your right. It will reach it’s highest at roughly 1:00 PM (not noon, because of daylight savings time). In the summer, the sun rises in the northeast (or slightly behind you if you’re still facing south) and sets in the northwest. In the winter, the sun rises in the southeast and sets in the southwest and makes a lower path in the sky.

    From the tropics, the sun rises nearly due east and sets nearly due west and passes high overhead all year long.

    From the southern hemisphere the sun moves right to left as you face north.

    If this didn’t help, visit your local library and browse through entry level astronomy texts….one will surely have some pictures that will help you. I teach astronomy part time at the local college and I know that visualizing (and explaining!) the movements of the sun and stars is sometimes difficult.

    I carry a $3 compass with me so I can predict where the sun and moon will be. It’s helped me many times.
     
  7. The astronomy folks have lots of programs for this. Do a Google search on something like planetary position and location in sky. Most of the software that does planets also does the sun and moon.
     
  8. Charles,

    Or I could try Ptolemy instead. He had the geometry wrong, but for calculations his geometry would work just as well as Galileo's, perhaps better.

    More seriously, I managed to find some sites myself doing a google search of the net for "position of sun in the sky". One at

    www.helioclim.net/com/appletsolargeom/AppletSolar_en.html

    has a Java applet which gives a graph showing the altitude as a function of solar time. The altitude and azimuth are given numerically as you move the cursor across the time axis. Unfortunately, with my browser and the current version of Java it is using, some of the fields are overwritten with text, so it is a bit hard to use.

    I'm not sure why my original google search yielded so little.

    I've also found other sites giving all the relevant formulas, and if I get interested enough, I can write my own software to do what I want.

    It would still be nice to see something with detailed three dimensional diagrams showing how the the correct (Coperinican) picture relates to the Ptolemaic picture of the sun moving about the Earth. The latter is what you see when you look up in the sky. I understood that completely at one point in all its subtle detail, but age and time take their toll.

    Jeff,

    The site you referred me to gives me a firewall error. I am behind a DSL/Cable router which provides a firewall of sorts through network address translation (NAT), but it shouldn't prevent packets from a distant web site from getting through. I think the problem is at the Navy web site. Either it isn't letting any non authorized users through or something about packets coming from a NAT system can't get through. I would be curious to know if others can get through.
     
  9. Redshift is a mutimedia astronomy program available I believe from Amazon and other book sellers. I have version 4. While it provides a lot more information than you may want it will allow you to position yourself anywhere on the planet, pick any date, anytime of day and show you the position of the sun, 250,000 other stars, asteroids, comets and 40,000 deep sky objects. You can place a pointer on the sun or any other object and it will provide exact coordinates. Like I said, maybe a bit of overkill but, who knows, you might find it pretty fascinating as I have.
     
  10. Leonard,
    I'm also NAT addressed from behind a DSL router/modem. I have no trouble. You might want to check your router settings.
     
  11. About access to aa.usno.navy.mil:

    This is getting stranger and stranger. I have three computers, runing Linux and Windows, two of which as dual boot, all connected to my DSL/Cable router. I can't see anything about the router settings that could affect the situation, and I don't believe I've ever had this problem with a publicly available website. I've tried Windows 98 and Linux on each of two computers. I've tried Mozilla, which is similar to Netscape, and I've tried both Netscape and Internet Explorer. In all cases but one, I was denied access to the site. The one success was using IE, but when I tried again with IE, I was again denied access.

    I wonder if some other people could try it with different browsers to see if I am unique. The only thing that occurs to me is that the site may have problems with browsers other than IE and after one attempt with a non-IE browser it excludes that IP address for some period of time.
     
  12. I can't get onto it either
     
  13. The last time I needed that info I called my local planetarium. Astronomers have great tables for where and when thing are located in the sky. I associate with astronomers and know there are quite a few programs out there that work everything out. Check for a local astronomy club or store.
     
  14. You're right, Leonard. I've been using this site every few weeks for two years without a problem. Now, all of a sudden, the Navy is verbotten.

    Guess we all can't be too careful, now that the burnoose is loose...
     
  15. I guess bin Laden might use the information he could obtain from the Naval Observatory to focus an enormous magnifying lens on the White House. ;-)
     
  16. I'm unable to access the Navy site also. I have used it in the past.
    The Nautical Almanac will not give the information you seek unless you solve a sight reduction problem in which case you would not need the Almanac. I believe the magazine "outdoor Photographer" publishes the info you seek...Richard
     
  17. I did a cut & paste of Jeff's link and got in no problem.... it's the Astronomical Application Dept. with Form A & Form B Table Computors .... right?
     
  18. http://aa.usno.navy.mil/data/docs/RS_OneDay.html

    Works for me.
     
  19. You are not authorized to view this page
    You might not have permission to view this directory or page using the credentials you supplied.

    --------------------------------------------------------------------------------

    If you believe you should be able to view this directory or page, please try to contact the Web site by using any e-mail address or phone number that may be listed on the aa.usno.navy.mil home page.

    You can click Search to look for information on the Internet.




    HTTP Error 403 - Forbidden
    Internet Explorer
     
  20. To those of you who managed to connect to the Naval Observatory,

    You might try again. I did manage to connect once, but I haven't any other time despite numerous attempts. I think there is a problem with the site or perhaps its link to some ISPs
     
  21. If I try from home (cable - *****.co.uk) I get refused. If I log on to a server at work (DSL - *****.com) and try it from there, I get in OK...

    The server at work runs NAT through a firewall, my home PC gets an IP address from the ISP (although I run it through Zonealarm - but I get the same result if I shut down ZA). Looks like it may be filtering based on IP addresses or possibly reverse DNS lookup (as the work firewall has an entry in DNS & my home PC does not).

    Anyway - I came across a program called MoonCalc which is as the name suggests intended for tracking the moon, but it also has displays data for the Sun too. No graphics for the Sun transit tho.... http://www.starlight.demon.co.uk/mooncalc/

    Cheers,
     
  22. The software you need is SunPath. This is what professional motion picture dp's use. Check it out. Just do a google search for SunPath and you'll be there.
     
  23. I've had the link I gave earlier bookmarked for years, use it fairly frequently and don't remember ever being denied. You might try another browser?
     
  24. There's a program, I think called "Sunpath", designed by a movie director for the location filmmaking industry. I know someone who uses it, and have seen it in operation- works quite well. I'd bet that it's just what you need.
     
  25. I am biased, but your best, most cost effective bet would be the Heavenly-Opportunity software available at http://weba.viawest.net/users/fcs/ho/
    This will do everything you want and mauch more.
    jb
     
  26. Sunrise, sunset, max altitude can be found here: http://www.heavens-above.com/countries.asp
     

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