Hi Roger,
I had to change the date format in colum A and in the formula of colum
E. Maybe this is of concern for others too.
It is a matter of taste of course to use a spreadsheet for this
calculation. I would prefer and recommend a free numerical software like
Scilab e.g.. Meeus's algorithm would appear readable and edits are easy
to make.
Regards, Helmut Haase
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Am 26.10.2016 19:05, schrieb Roger Bailey:
Hi Dan,
The advice you have received from Gian and others is excellent. I use
his "Sol et Umbra" android app in a smartphone and tablet. It is a
great app.
But you asked for a spreadsheet. Attached is one implementation of
Meeus's simplified solar coordinate calculation. Helmut Sonderegger
developed this and added it to my spreadsheet for calculating
analemmatic sundials. I have copied it into several other
spreadsheets whenever I needed declination and the equation of
time. This is a reduced version small enough to get through the SML
size filter. Input the start date and time into cell A7. Change the
increment from 1 day to whatever in cell A8. Copy row 8 and paste it
in below for as many rows as you wish. Copy the spreadsheet into other
spreadsheets using solar coordinates but be aware of the absolute
address to the degree to radian conversion in row 1
I answered this question about a year ago for Jack Aubert. he was
interested in the rate of change of declination near the equinox and
solstice. I sent him a full implementation of that included
calculating and plotting the time of sunrise near the winter
solstice. The copy to the SML was filtered out but I will forward his
note and my reply with the original spreadsheet.
To answer this question I needed to review Meeus's Astronomical
Algorithms, specifically Chapter 25 Solar Coordinates pg 163-170. This
great reference book is now available as a free download. Just Google
Meeus Astronomical Algorithms free. Is this an example of fair use, a
single copy of a library copy or a copyright violation? I don't know
but I was glad to find it. meeus discusses the accuracy of the simple
calculation compared to the more rigorous version. For sundials the
simple version is fine.
Regards, Roger Bailey
*From:* Dan-George Uza <mailto:[email protected]>
*Sent:* Tuesday, October 25, 2016 9:38 AM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Solar Declination
Hello,
Can you provide a free accurate spreadsheet for the calculation of
daily solar declination across a leap year as well as non-leap year?
Thanks,
Dan Uza
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