WHAT IS THE BEST TIME FOR METEOR SCATTER OPERATION?SPORADIC METEORS
In the morning hours, around 0600 local time, that part of the earth is facing the same direction as the direction of travel of the earth in its orbit around the sun. Thus, not only are meteors swept up which are heading toward the earth, but the movement of the earth around the sun allows it to catch up with some of the slower meteors and pull them in, also.
On the evening side (facing away from the direction of the earth's orbit), the only meteors reaching the earth are those which can overtake it.
The best time for visual observing is considered to be between 2 and 4 am local time. This is because during the season when the sporadics are at their peak (summer), the sky brightness is increasing after 4 am.
It must be remembered, however, that many or probably most "sporadic" meteors are actually the remains of long-gone showers. Thus, on a given day, there could be meteors from 5 or 6 of these "extinct" showers hitting the atmosphere, causing an enhancement at an unexpected time.
There is a considerable seasonal variation of sporadics, also, with February being the low month and July being the highest. (KB0VUK has a chart of this on his Web page). Note the number of major and minor showers in the June-September period and the reason for this will become obvious.
There are also several other factors that influence the number of sporadics, and also the ratio of morning to evening. But these are not that important. Just be aware that the variation can be significant month to month, day to day, and even minute to minute!
The best reference for MS operation is still the second article by W4LTU, reprinted in "Beyond Line of Sight" (available from the ARRL). This is NECESSARY reading for anyone thinking of MS operation. Also, see the text files that accompany OH5IY's MS-Soft program.
Yes, HSMS is possible any time. But there are 4 to 6 times the average number of sporadics at 6 a.m. local time than at 6 p.m. On a good path, evening HSMS operation is quite possible; and the pings, while fewer, often seem to be stronger in the evening. (On a difficult path, unless there's a shower peak, I wouldn't try evenings. There just are not enough sporadics).
SHOWERSThe peak of a shower may come at a time other than the 4-8 a.m. period, of course. In this case, the maximum rate may be at some other time of night (or day - remember that there are a number of daylight showers, too. These are seldom mentioned because visual observers can't experience them).
Some showers are spread over several days, others have VERY sharp peaks. As of now, these peaks can be predicted only very generally, and may be off by many hours. Their intensity may be off by an order of magnitued or more, also. This is because all predictions in the past have simply placed the probable peak time at the time when the earth's orbit should cross the orbit of the meteor stream. However, this does not take into account any variations, simply assuming that the meteors are now spread out evenly in their orbit. But, as has been realized in the past decade, this often is not true. Especially for streams that may have established a resonance with Jupiter, a stream may be bunched in filaments, as the Leonids have proved to be. Because of the work of Asher, McNaught, and others, predictions in coming years may begin to improve greatly in accuracy. For more on this subject, go to The Upcoming Leonids Storms, the Archived News Page and also the pages of Asher and McNaught, who are revolutionizing meteor shower predictions with their dust-trail model.
The big mistake most operators make during a shower is trying to operate using shower meteors when the shower radiant is below their horizon. The radiant is the point in the sky from which the meteors appear to come. If this part of the sky is still below the horizon, the number of shower meteors available for your use is going to be near zero! Yet during every major shower, stations will be heard on 144.200 calling and calling long before the radiant rises; then later they talk about how poor the shower was!
If you're operating HSMS, you may be able to catch enough sporadic meteors almost any time of day or night, even during the early evening. However, for slow CW or SSB, when overdense bursts or a number of good underdense pings are needed, it is of little value to operate when shower meteors are not expected! See the tables in W4LTU's articles, or use OH5IY's MS-Soft program to determine the rise and set time of the radiants of the various showers. (You will also note that, until the radiant's elevation is up 30 degrees or so, it isn't considered a very good time for their utilization).