天琴座流星雨辐射点位置移动星图

The λ⊙ = 32.32° timing given above is the 'ideal' maximum found in IMO results from 1988—2000. However, the maximum time was variable from year to year between λ⊙ = 32.0°—32.45° (equivalent to 2012 April 21, 21^h30^m to April 22, 08^h30^m UT). Activity was variable too. A peak at the ideal time produced the highest ZHRs, ∼ 23, while the further the peak happened from this, the lower the ZHRs were, down to ∼ 14. (The last very high maximum was in 1982, when a shortlived ZHR of 90 was recorded.) The mean peak ZHR was 18 over the thirteen years examined.

While generally thought of as having a short, quite sharp, maximum, this investigation showed the shower's peak length was inconstant. Using the Full-Width-Half-Maximum time (the period ZHRs were above half the peak level), a variation between 14.8 to 61.7 hours was detected (mean 32.1 hours). The best rates are normally achieved for just a few hours even so. The analysis also confirmed that occasionally, as their highest rates occurred, the Lyrids produced a brief increase in fainter meteors. Lyrids are best viewed from the northern hemisphere, but are visible from many sites north and south of the equator. As the radiant rises during the night, watches can be carried out usefully after about 22^h30^m local time from mid-northern sites, but only well after midnight from the mid-southern hemisphere. New Moon on April 21 makes this year perfect for Lyrid maximum observing, and if the ideal peak time recurs, it should be best-seen from sites across much of North America, particularly the eastern half. Remember, other maximum times are perfectly possible!

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