The duration of this stream extends from March 13-April 17. Maximum occurs
over the period of March 31-April 2, from an average radiant of RA=285 deg,
DECL=+69 deg. Visual observations reveal low activity from a radiant 2 deg to 5
deg across.
History
This stream was first recognized in a 1973 study involving 2401 photographic
meteor orbits obtained during the Harvard Meteor Project of 1952-1954. The study
was conducted by Allan F. Cook, Bertil-Anders Lindblad, Brian G. Marsden,
Richard E. McCrosky and Annette Posen. They identified four meteor orbits, which
formed the "Delta Draconids." Possessing a duration covering March 28-April 17,
the average radiant position was given as RA=281 deg, DECL=+68 deg.
Shortly after the above photographic data was published, Zdenek Sekanina
published the third paper in his four-part "Statistical Model of Meteor Streams"
series. Covering the period of 1961-1965, it listed 72 minor meteor streams, one
of which was the "Tau Draconids." This stream was given a duration of March
24-April 12. The nodal passage came on April 1.7 (Solar Longitude=11.5 deg), at
which time the radiant position was RA=291.6 deg, DECL=+71.3 deg. The last paper
of that series was published in 1976 and covered the period of 1968-1969. The
Tau Draconids were again detected‹this time with a duration extending from March
12-April 12. The date of the nodal passage was given as March 27.0, while the
average radiant was RA=286.4 deg, DECL=+69.1 deg.
The first visual observations of this shower were actually occurring while
Sekanina's second session of the Radio Meteor Project was in progress. On March
25.92, V. K. Leichenok, N. S. Malikov, L. M. Afanas'eva and T. A. Kopycheva
plotted more than 10 meteors from a radiant of RA=280.0 deg, DECL=+73.0 deg. The
radiant diameter was determined as 5.0 deg.
As a follow-up to the 1969 observations, the Russian observers strove to
confirm the many radiants they had found by conducting another extensive visual
survey in 1973. On March 26, S. V. Safonov plotted three meteors from a 1.5
degree diameter radiant at RA=272 deg, DECL=+72 deg. During March 27-29, N. V.
Smirnov plotted six meteors from a 2.0°-diameter radiant at RA=285 deg, DECL=+71
deg.