Solar Coordinates of Observed Sun Spots

by L.Bogan (January 1999 - update: December 2011)
Cambridge Station, NS
This web page will show you how to measure the position of sunspots on the disk of the Sun and provides a Java Script program to determine their solar longitudes and latitudes. The program also calculates the Solar orientation angles for your date and time. Your browser must have its Java Script interpreter enabled
  1. Equipment
  2. Procedure
  3. Analysis
  4. Measurements
  5. Forms and Java Script Program

Java Script Calculation of the Solar Orientation Angles
and Solar Latitudes and Longitudes of a Sun Spots

First: Enter the Date and Time
of Observationand Calculate
the Sun's Orientation

Year Month
Day Hour(UT)


Solar Orientation Results

Carrington Number
Rotations since Nov 8,1853
Longitude of Center of the Disk, Lo degrees
Latitude of Center of the Disk, Bo degrees
Position Angle of the Rotation Axis, P degrees

Calculation of Sunspots Solar Latitude and Longitudes

Instruction for Measuring Spots

AFTER Calculating the Orientation of the Sun
Enter the radius and position angle for spots observed in the table below
(Enter 0's in unused spaces)

Radius of Solar Image =
Use the same units for all linear measurements. Angles are all in degrees.
SPOTS Spot#1 Spot#2 Spot#3 Spot#4 Spot#5 Spot#6
Distance from the center, r
Position Angle(degrees)
latitude, B (degrees)
longitude, L (degrees)

Comments to Author: Larry Bogan