Solar elevation and azimuth.

Discussion in 'Earth Science' started by IanUK, Nov 28, 2017.

  1. IanUK Registered Member

    Messages:
    4
    Having built a solar air heater I want to use my Raspberry Pi to track the sun across the sky to see whether the energy requirement to do this are worthwhile from an efficiency point of view in a northern latitude. I had considered using a sensor to measure solar intensity and hence track solar movement that way. However, I would like to calculate the Suns position (elevation and azimuth) hour-by-hour throughout the day. Unfortunately I cannot find a set of equations that will allow me to do this. Can anyone help me?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Seattle Valued Senior Member

    Messages:
    2,573
    Timojin would be your man.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. exchemist Valued Senior Member

    Messages:
    6,637
    I found here: https://stackoverflow.com/questions/15056269/pyephem-can-i-calculate-suns-altitude-from-azimuth that there appears to be a program called PyEphem in Python, that does this. However I have not dug any further. Maybe you might follow this up and see if if it gives you what you want. The guy says he is at Stonehenge so he's in Britain at least, which may help a bit.
     
    IanUK likes this.
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. exchemist Valued Senior Member

    Messages:
    6,637
    You have a wicked sense of humour.

    Please Register or Log in to view the hidden image!



    But Janus might know.
     
    Seattle likes this.
  8. IanUK Registered Member

    Messages:
    4
    Many thanks. This looks very promising. I'll download it at take a closer look in the next few days. I'll let you know how I get on.
     
  9. paddoboy Valued Senior Member

    Messages:
    21,647
    I once learnt to use a marine sextant, and part of that exersise was checking a Nautical Almanac re position and angle of the Sun to the horizon. If you can get your hands on one of those, it lists in second increments the height of the Sun above the horizon.
     
  10. paddoboy Valued Senior Member

    Messages:
    21,647
  11. IanUK Registered Member

    Messages:
    4
    Thanks for your input. The almanac would certainly provide me with the opportunity to establish elevation and azimuth. There are also a number of good online calculators like keisan.casio.com. By using something like these I could build a table from which my attitude control program could extract data for positioning the solar heater. However, using a set of equations to calculate azimuth and altitude from within the program is the neatest way of doing it. The python software identified by exchemist seems a promising way forward.
     
  12. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    I am not sure what you are trying to do with your solar collectors if anything.
    Are you trying to work out if setting up so the collectors follow the Sun?

    A Sun dial may feed you the angles..in fact its fun working out a Sun dial from scratch.

    The mid day Sun over 12 months marked out a figure eight like pattern. Or think of the Egyptian symbol for eternity...they no doubt observe the Sun at mid day.
    Alex
     
  13. DaveC426913 Valued Senior Member

    Messages:
    7,314
    An analemma.

    As of yesterday, my office workstation now has a wall-to-wall, floor-to-ceiling south-facing view of the city from the 15th floor. I have already begun constructing an analemma on the window using dry erase markers. So cool.
     
  14. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    Thanks Dave.
    I would be very tempted to set up a timer and camera in what I hope is a secure location...you could produce a jar dropping photo... The city the Sun.. I assume to get a nice city view and the analemma.
    Alex
     
  15. DaveC426913 Valued Senior Member

    Messages:
    7,314
    That would be cool.

    I'm oft-tempted to do this for a whole host of subjects, from plant growth to building construction. Alas, I don't have multiple cameras kicking around that I can relegate to a task that will take them out of commission for a year or more. Never mind how I would keep them from getting nicked.

    And alas, in my industry, I cannot count on being in one company, let alone one location for that long.

    (The place we just moved from had an East-facing window. I contented myself with sketching the entire scene outside the window using a dry erase marker and a fixed observation point. Had to keep updating the sketch over the fall as leaves fell, and more scenery came into view. I left it on the window as an Easter Egg for the next occupant in my cubie.)
     
  16. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    When I get out of the city permanent and set up my observatory again...my last one empty was taken cause I was away so long ... I plan to catch it.
    There is a bit in it but given the time that's the sort of stuff I enjoy.
    Could take a long time some days have cloud ... Probably three years all going well but probably longer...which makes it even note cool? I wonder if it would move in the sky? Will last years be in exactly the same place...must find out.
    Alex
     
  17. DaveC426913 Valued Senior Member

    Messages:
    7,314
    With 365 possible data points, it wouldn;t be a hardship if you missed a bunch.

    In fact, judging by the analemmae I've seen, you're going to want to not take every day, since they'll virtually overlap.
    You might sift through your pics and decide to only include every 4th day or so in the final composite. That's still 90 data points in your pic.

    Please Register or Log in to view the hidden image!

     
  18. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    Yes but less than a photo of the Sun for each spot would not cut it for me.
    The difference day to day must be...mmm I can work it out photo size etc ...although not a math person its easy to work out...mmm it moves thru from one tropic to the other over half a year so in on day about 40 degrees by 365/2...I have done it my head before going to sleep.
    There are weather cams that probably would do it...
    Anyways won't happen while in town.
    Alex
     
  19. DaveC426913 Valued Senior Member

    Messages:
    7,314
    Well the Sun subtends 0.5 degrees of the sky - same as the Moon.
    The Earth tilts by 47 degrees over the seasons, so the analemma spans 47 degrees.

    Since the analemma is about 180 data points tall, that'll work out to 180 discs over 47 degrees. Or just about four discs per degree (on average**). And one disc is 0.5 degrees in diameter. So, huge overlap.

    **True, during the equinoxes they would be farther apart --- but during the solstices, the Sun moves so little that the discs will totally overlap, forming a continuous line one-sun-width thick.

    You actually lose information, by including too much data.

    Oh wait. Here's a pic of what I just described:

    Please Register or Log in to view the hidden image!

     
    Last edited: Nov 29, 2017
  20. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    Hows this for cool and artistic...in your garden a device to hold a lens away from a curved wood bowl a d burn it in the wood.
    May be problems off axis burning.
    Alex
     
  21. Xelasnave.1947 Valued Senior Member

    Messages:
    3,360
    Thanks so cool
    Alex
     
  22. sideshowbob Sorry, wrong number. Valued Senior Member

    Messages:
    3,041
    I did that at the hockey arena where I used to work, by measuring the shadow of a window on a dressing-room wall.
     
  23. IanUK Registered Member

    Messages:
    4
    Many thanks for this. A bit of difficulty downloading but it does the job perfectly!
     

Share This Page