The curve of the sun?

Discussion in 'Off-Topic Members Lounge' started by 24Volts, Mar 20, 2017.

  1. 24Volts

    24Volts

    Joined:
    Mar 21, 2010
    Messages:
    141
    Likes Received:
    0
    Hello,

    In reference to the following link:

    http://www.physicalgeography.net/fundamentals/6i.html

    In reference to the graph on page 2 of 4 (Fig. 6i-2). What are they trying to tell me? If we look at the 50 degrees North line (The red one), It seems that approximately in mid June, the maximum hours of day length should be:

    Sin(50) = 77% of a 24 hour day!

    The maximum hours of the day should equal to = 0.77*24 = 18.4 hours

    Why is the graph pointing more towards around 16 hours??

    any help would be very appreciated!

    Bob
     
    24Volts, Mar 20, 2017
    #1
    1. Advertisements

  2. 24Volts

    Arouse1973 Adam

    Joined:
    Dec 18, 2013
    Messages:
    4,953
    Likes Received:
    1,007
    Location:
    Cornwall U.K
    I take it as the sin function is used for the intensity of the sun not the length of the day. I might be wrong though.
    Thanks
    Adam
     
    Arouse1973, Mar 20, 2017
    #2
    1. Advertisements

  3. 24Volts

    Gryd3

    Joined:
    Jun 25, 2014
    Messages:
    4,061
    Likes Received:
    862
    Location:
    Fraser Valley. Canada, BC
    You got two sections mixed up!
    The sin(50) you are using is talking about light intensity based on the angle of incidence, and the graph you are looking at it indicating the length of day over time... The 50 degree line on our globe does not equal the angle of incidence...
    I'm sure there is a proper formula for what you want to calculate... it will need to take into account the angle of our Earth's axis, the degree North or South of the equator, and our relative position from the sun. It's not quite as easy as using a trig function by itself
     
    Gryd3, Mar 21, 2017
    #3
  4. 24Volts

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Joined:
    Jan 21, 2010
    Messages:
    22,450
    Likes Received:
    1,866
    Location:
    Mid way between Beijing and the Ronne Ice Shelf
    It's more complex than that.. If it were that simple you would have to be at exactly 90 degrees of latitude to have 24 hours of daylight . As you can see, 70 degrees is sufficient to get 24 hour long days.

    I suspect that 66.5 degrees would be sufficient to get at least one 24 hour day due to the Earth's (current) tilt of 23.5 degrees.
     
    (*steve*), Mar 23, 2017
    #4
  5. 24Volts

    24Volts

    Joined:
    Mar 21, 2010
    Messages:
    141
    Likes Received:
    0
    Thanks all for your replies,

    I would simply need to know where at a given latitude degree (ex: 45Deg North = Montreal), how much daylight is available every day throughout the year (365 days) based on the sunrises and sunsets. In other words for example, lets pick a date at random... suppose I want to know what time the sun comes up (Sunrise) and what time it goes down (Sun set) on September 25. I may may need this information for June 9th... or Dec 25 etc...

    Also, I would need the same daylight between susnset and sunrise informations for different locations for example, Mexico (which is at 23Deg North).

    Is there a simple formula to calculate this?

    Thank you for al your help
     
    24Volts, Mar 27, 2017
    #5
  6. 24Volts

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Joined:
    Jan 21, 2010
    Messages:
    22,450
    Likes Received:
    1,866
    Location:
    Mid way between Beijing and the Ronne Ice Shelf
    There is no simple formula, but the calculations are not magic.

    The hardest part is determining the local time at a location because this is affected by politics as well as mathematics. Cannulating GMT time is easier.

    Many web sites used for projecting solar panel performance can do these calculations. The length of the day is more important than the actual sunrise and sunset times.

    Assuming a constant tilt in orbit and an integer number of days in a year simplifies calculations without much loss in accuracy as the difference from one day to the next is minimal.
     
    (*steve*), Mar 27, 2017
    #6
    1. Advertisements

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
  1. wade7575
    Replies:
    10
    Views:
    944
    (*steve*)
    May 26, 2017
  2. Mahonroy
    Replies:
    9
    Views:
    482
    CDRIVE
    Sep 17, 2016
  3. Lawrenciumbc
    Replies:
    7
    Views:
    605
    Lawrenciumbc
    Sep 20, 2016
  4. Name...
    Replies:
    15
    Views:
    211
    Name...
    Mar 15, 2017
  5. Banggri

    What's the importace of the resistors in THS3202?

    Banggri, Mar 4, 2017, in forum: Datasheets, Schematics, Manuals and Parts
    Replies:
    3
    Views:
    110
    davenn
    Mar 4, 2017
  6. ayylmao

    Is the Temperature Coefficient of the Capacity stated

    ayylmao, Mar 7, 2017, in forum: Datasheets, Schematics, Manuals and Parts
    Replies:
    2
    Views:
    90
    ayylmao
    Mar 7, 2017
  7. Lilybell
    Replies:
    1
    Views:
    88
  8. sino007
    Replies:
    6
    Views:
    150
    Minder
    Mar 28, 2017
Loading...