analemma

analemma, a Python code which evaluates the equation of time.

The code computes and plots the equation of time, the declination, and an analemma curve for various orbital parameters. The analemma is the curve traced by the position of the sun, measured at clock noon, over a year.

Usage:

analemma ( ecc, lon, obliq )

• ecc, the eccentricity;
• lon, the perihelion longitude in degrees;
• obliq, the axial obliquity in degrees;

The code with no options uses the following default values:

• eccentricity = 0.01671;
• longitude of perihelion = 1.347 radians = 77.18 degrees;
• axial obliquity = 0.4091 radians = 23.44 degrees;

Licensing:

The computer code and data files described and made available on this web page are distributed under the MIT license

Languages:

analemma is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and codes:

Reference:

1. Brian Tung,
   Figure Eight in the Sky, a new perspective on an old fascination,
   Astronomical Games, August 2002,
   https://www.astronomycorner.net/games/analemma.html.

Source Code:

• analemma.py, the source code.
• analemma.sh, compiles the source code.
• analemma.txt, the output file.

• analemma.png, the PNG file of the analemma.
• declination.png, the PNG file of the declination.
• eot.png, the PNG file of the equation of time.