# The features of minor-shower observations

Minor showers are called so since they produce little activity for the visual observer. Generally we define a minor shower as being one whose maximum hourly rate (HR) is less than about 10. Admittedly, this is an arbitrary limit but it is a suitable one for our purposes. It does not make sense to define the limit distinguishing between minor/major showers using their ZHR. The observing technique described here is appropriate when the observed number of meteors does not exceed a certain limit, because this method leads to a certain amount of dead-time. Of course, the time loss must not be significant for the aim of the observation. As already pointed out elsewhere, the main goal of visual observations is the reliable determination of physical shower parameters. Therefore, we consider showers which produce less than 10 meteors per hour to be minor showers. For these, plotting is an essential observing method.

This means the number of shower meteors visible during an observation is considerably smaller than for major showers. These small numbers cause specific problems that we now deal with. Strictly speaking, at the beginning and the end of their activity periods, major showers are effectively minor ones as they suffer from the same problems.

Sporadic activity occurs throughout the year. In the sky the paths of sporadic meteors seem to be nearly randomly distributed. Thus sometimes it happens that the backwards extension of a sporadic meteor track accidentally meets with a shower radiant. Thus shower data usually contain a certain contribution from sporadic meteors. This effect is called "sporadic pollution" and is of the order of 1-2 meteors per hour (m/h).

Imagine a sporadic pollution of 2 m/h. Observing a major shower of 80 meteors per hour, the relative error result is only 2.5% but for a minor shower of 4 m/h it amounts to 50%! Therefore, sporadic pollution is the main problem in observing minor showers. If we want to obtain reliable results we must reduce it. In the following sections you will learn how this can be achieved.

You will see that this requires a lot of knowledge and experience. Tens of observing hours will be necessary to obtain sufficient skill. But are your results obtained in this learning phase completely worthless for analyses? By no means! As long as you think that you are still unable to provide reliable data for the minor showers, simply report the total of meteors seen. In the table of the report form "Observed numbers of meteors per period and per shower" only fill in the column "Tot" and in the table "Magnitude distributions" only give the total magnitude distribution. Even these data about the total activity can be used for some analyses.

In this way you can learn step by step, without the pressure to report the whole bulk of necessary data in the correct way from the first observations. In this learning phase, try to plot the meteors, to report all the data, and to assign the meteors to the different showers as outlined in this chapter until you estimate that your data can now be considered reliable.

It may also be that you do not wish to go so deeply into meteor observing. In this case try to plot the meteors you see using the method described in Section 7 and send the recorded meteor data and the maps to the IMO officer for visual observations. This means you are not forced to deal with the rather difficult problems of minor-shower observations, but despite this fact, your data will be of scientific use.