The relative sunspot number is calculated by counting the number of sunspot groups, multiplying this figure by 10 and then adding the total number of sunspots that are present on the disk. Any discrepancies in the two data lines are due mainly to weather, as the ISN number is counted from many world wide observatories, while the WAS figure is based purely on observations made by members in the local area. Above right is a photograph of the Sun taken on 1999 October 16, and to the right is a drawing made on 2000 March 19 by Brian Halls. Click on the drawing to see it in greater detail.
Astronomers normally try to use the largest aperture they can to capture as much light as possible.
The Sun however usually gives the astronomer more than enough light and even small telescopes may be used to study the finer details on the Sun. Without doubt the safest method of observing the Sun is by projecting its image onto a white screen. This is the method used by the members of the Society. Beginners to solar observing are recommended to seek their advice, ideally at one of the regular observers mornings, when the correct techniques can be demonstrated. The photograph, at left, shows Graham Boots, Curator of the Observatory, observes sunspots by projecting the Sun's image on to a piece of white card.