From: Roger Bailey Sent: Wednesday, March 04, 2015 5:28 PM To: Michael Ossipoff Subject: Re: Jack: Duration of sunlight on a particular day
Hello Michael, I responded to Jack and provided a spreadsheet that calculated sunrise and sunset times that included the option for refraction. This spreadsheet also included Meeus Algorithms to calculate the equation of time and convert solar time to clock time. This spreadsheet was developed to show the sunrise and sunset shifts near the winter solstice but the start date is optional. All the options are in blue type. The detailed calculations are in a faint type. I included the spreadsheet in my reply to Jack with a cc. to the list but this response was never posted. The spreadsheet is attached to this reply to you and anyone on the list who is interested can send me a request. Jack found spreadsheet and the chart tab quite useful. Regards, Roger Bailey From: Michael Ossipoff Sent: Wednesday, March 04, 2015 6:51 AM To: sundial@uni-koeln.de Subject: Jack: Duration of sunlight on a particular day Jack: You wrote: I have been trying to figure out how to plot the duration of daylight over > the course of the year as a function of latitude. (I would generate a > curve for each latitude I am interested in.) [endquote] You said to disregard physical effects such as atmospheric refraction (and solar semi-diameter?). That simplifies the formula. Where h is the number of equal sundial-hours before or after solar noon at sunrise or sunset; dec is declination, and Lat is latitude: cos h = - tan Lat * tan dec. Double h, and that's the sunlight duration for that day, the day corresponding to some particular value of dec, at some particular latitude Lat. And yes, _lots_ of people at this list know that. I'm not posting something new. But I just wanted to mention it because I haven't seen it in the answers so far. Michael Ossipoff -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial -------------------------------------------------------------------------------- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.5751 / Virus Database: 4299/9221 - Release Date: 03/03/15
SolsticeRiseSet.xls
Description: MS-Excel spreadsheet
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