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BAA Solar Section Aims & Objectives

(Revised December 2006)


To promote every aspect of solar astronomy and to provide information and encouragement in relation to the study of the Sun.


Solar Section Program of Work

1. For observing naked-eye spots a safe solar filter (such as Welders glass, shade 14, mylar film, or inconel filter) is a necessary. DO NOT USE ANY OTHER MATERIAL no matter how dark it appears. If in doubt about the safety of any solar filter contact the Director for advice before using it.

When a naked eye sunspot is seen, a note should be made of the date and time, whether the spot was seen easily or only just glimpsed, and on which part of the disk it appeared. It will then be easy to identify the spot from whole disk drawings. If two or more spots are seen near to one another, a brief note should be added to indicate their relative positions.

On no account should naked-eye observations be preceded by a telescopic examination of the Sun to ascertain that spots are actually present. Naked-eye observations are of no value statistically if the positions of the spot are known in advance.

2. Counts of Active Areas (AAs) and the Relative Sunspot Number (R) are made from either whole disk drawings, or directly from the Sun itself. Projection of the Sun's disk onto a white card is probably the best method of use. Be especially careful to look out for any very small spots (usually called pores) on the disk as these can be easily overlooked. The notes below give the rules to be followed.

Active Areas (AAs)

Every spot, however small, counts as a separate Active Area if it is at least 10o of latitude or longitude from its nearest neighbour. The same rule applies to spot groups.

A large group, however, spread out in area, is still one Active Area unless it has distinct separate centres of activity at least 10o apart.

From time to time distinct groups do break out nearer than 10o from each other. This is mostly in latitude which be in the order of 5o. When such groups occur they should be counted as two AAs and a note made that this has been done.

Relative Sunspot Number (R)

To find the Relative Sunspot Number proceed as above then count all the spots that you can see either singly or within groups. For the purpose of this exercise, the Relative Sunspot number = 10g + f. Therefore "g" represents your AAs and "f" the number of spots counted within your AAs. The final calculation that has to be made to get R is therefore to multiply "g" by 10 and then add "f".

A monthly report form is used to record both Active Areas and Relative Sunspot Number counts. In each observing day the number of AAs and the R is noted: non-observing days are left blank. If you wish only to record AAs, fill in the column marked "gn" (AAs in the northern hemisphere), "gs" (AAs in the southern hemisphere) and "g" (total Aas north and south), add them up at the end of each month and calculate your Mean Daily Frequency (MDF) by dividing the total by the number of observing days. If you cannot distinguish between north and south on the Sun's disk just fill in "g".

For R fill in the "gn", "gs" and "g" columns on the monthly report form as before and then count all the spots that you can see either singly or in groups and put this total into the appropriate "fn", "fs" and "f" columns. To fill in the R column multiply "g" by 10 and add to "f" to get R for each day. At the end of the observing month, calculate your monthly R by dividing the total of the R column by the total number of observing days that month.

Note: "gn" = AAs in the North; "gs" = AAs in the South; "g" = total AAs; "fn" = all spots counted in the North; "fs" = all spots counted in the South; and "f" = total number of spots counted. The completed form should be sent to the Director as soon as possible at the end of each month.

3. Whole disk drawings showing the positions and types of spots should be made on the 152mm (6-inch) diameter solar blanks obtained from the Director. On each sheet on which a drawing is made should be written the date and the time of observation, the type of telescope used and the method of observation, a brief note of the observing conditions, the rotation number and the values of P, Bo and Lo obtained from the BAA Handbook, and the observer's name.

4. If possible, a series of drawings of complex spots or groups of spots should be made. These will show the course of growth and decline of the disturbances. Single drawings, however, will be useful as they can be associated with the drawings of other observers.

5. Occasionally a large spot occurs in which the umbra is not uniformly dark but is marked by brownish or reddish patches which are brighter than the normal dark umbra. Drawings should be made of any of these peculiar spots which may be seen. The coloured patches could be indicated by differential shading or the use of a red pencil would be an improvement. These red patches are best seen when the spot is near the centre of the disk. When making these observations, chromatic aberration in the optical system should be borne in mind.

6. When conditions permit, the outlines of bright faculae should be shown on the drawings in addition to the spots or, better still, the faculae patches can be indicated with yellow pencil.

7. Polar faculae appear as bright points of light, a few seconds of arc in diameter, on the north and south polar caps usually above 60o latitude. They are not grouped so as to form luminous patches like the faculae found at lower latitudes, but are scattered at random. They are best observed in a darkened observatory by projection using an equivalent disk 250mm (10 inches) or more in diameter. Good seeing is essential.

8. For tracing the life histories of spots and spot groups, a series of good photographs are particularly useful. They should be correctly orientated with North at the top. Also the date, time in UT and the latitude and longitude of the subject should be added.

9. The distribution of prominences around the disk should be recorded as far as possible, their proportional sizes and latitudes, North and South being recorded separately. It is also useful to divide this count into prominences seen in the spot zone latitudes 0o - 40o, and those seen at the higher latitudes 40o to the poles. A total MDF is made at the end of the observing month in the same way as for AAs.

As with drawings of individual spots and groups, a series of drawings of prominences showing their changes would be useful, as would photographs. Prominences usually appear pinkish red and should be labelled as either active or quiescent. Filaments usually appear black or dark brown are really prominences seen against the Sun's disk. These should be noted if they show any motions or activity, any sudden disappearances etc.

The positions and intensity of solar flares should be noted, preferably using the scale of brightness:

Sf = sub flare 1n 1b 2n 2b 3n 3b 4n 4b where n = normal and b = bright.

It is important to accurately report the time of these events. Anybody who is about to take up the observation of flares should seek further advice on this important subject from the Director of the Solar Section.

Monthly report forms, Hydrogen Alpha forms and Disc Drawing form masters can be downloaded from Here. Lyn Smith, Director BAA Solar Section

Contact Lyn