Scientific Programs


One of the major objectives of the society is to promote the science of Astronomy through scientific programs in observational astronomy and other fields. These programs enable professional and nonprofessional astronomers to engage in research studies in collaborative effort.


I. Philippine Solar Index Program

As the center for astronomical data archiving and requisition in the country, the Astronomical League of the Philippines is responsible for producing the Philippine Sunspot Number (Rp) and Group Sunspot Number (Rg) with the assistance of astronomers sending sunspot data to the society.

The relative sunspot number or Wolf Number is computed using the equation Rp = k(10g +s), where: Rp corresponds to the Philippine Sunspot Number; g = number of visible sunspot groups; and s = total number of individual sunspots. The k-coefficient used is unity or 1.

The group sunspot number is computed by averaging monthly group counts by individual observers.

The current coordinator of the Philippine Solar Index Program is Raymund John Ang.


  1. Observers are requested to make observations of sunspots using direct or projection method. Full aperture filter must be placed over the objective for direct viewing. Note that the use of eyepiece solar filters is extremely hazardous and can cause irreversible blindness. Although the projection method yields lower resolution, it is recommended for beginning solar observers. Remember to cover the finder scope to avoid accidents and injuries. Use of cheap eyepiece models for projection is advised since the setup may result to damage to the eyepieces, especially in prolonged use.
  2. Telescopes with clear aperture of 50 - 80mm should be used when monitoring sunspots. If using medium to large aperture equipments, use an aperture stop to reduce effective aperture to about 80mm. Useful magnification for sunspot observations is from 40 - 100x. Low and high magnification scanning of solar surface is advisable.
  3. Be sure to count all visible groups and spots. The relative sunspot number devised Wolf is adopted in computing for the Philippine Sunspot Number (Rp) with k-coefficient set to unity or 1.
  4. For the Group Sunspot Number (Rg), individual group count should be made.
  5. Sunspot data must be sent to the Coordinator on or before the 10th day of the proceeding month for inclusion in the Solar Bulletin section of the Philippine Journal of Astronomy.


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