This shower exhibits a typically long duration that is a major characteristic of ecliptic streams–extending from December 14 to February 14. Maximum occurs around January 17 (λ=297.3°) from an average radiant of RA=128°, DECL=+20°. A secondary center may lie about 5° to the south with a very weak maximum occurring around January 19 (λ=300.1°) from an average radiant of RA=133°, DECL=+14°. The daily motion of the Delta Cancrid stream is +1.0° in RA and -0.2° in DECL.
The earliest detection of this shower seems to have occurred during the 1870’s. During 1872 January 1 to 15, members of the Italian Meteoric Association observed 7 meteors from an average radiant of RA=130 deg, DECL=+24 deg, while on 1879 January 12, a fireball was observed from RA=133 deg, DECL=+19 deg.
Indications are that this is a fairly weak shower, whose presence has not been consistently noted in the literature. Cuno Hoffmeister’s 1948 book Meteorstrome lists three probable radiants: one occurring in 1915, while the other two were observed in 1937. Although a few traces of this shower are found in a few sources published during the 1920’s and 1930’s, it should be noted that the extensive records of the AMS reveal no indication of activity from this radiant.
Perhaps the first solid evidence supporting this stream’s existence came in 1971, while Bertil-Anders Lindblad examined the photographic meteor orbits obtained during the Harvard Meteor Project of 1952-1954. Seven meteors were found which indicated a duration of January 13 to 21 and an average radiant of RA=126 deg, DECL=+20 deg.
Strong support of Lindblad’s findings came in 1973 and 1976, when Zdenek Sekanina published the results of the two sessions of the Radio Meteor Project conducted at Havana, Illinois, during the 1960’s. The first session covered the period 1961-1965 and detected 27 meteors during December 28 to January 30. The date of the nodal passage was given as January 13 (λ=292.2°), at which time the radiant was at RA=123.7°, DECL=+20.9°. The second session covered the period 1968-1969 and detected 37 meteors during December 14 to February 14. The nodal passage came on January 17 (λ=296.4°) when the average radiant was RA=129.8°, DECL=+19.8°.
After the details of the photographic and radar surveys had been published, visual observers began to search for the Delta Cancrids. The first came on 1974 January 19, when Bill Gates (Albuquerque, New Mexico) detected two meteors in 3 hours 46 minutes of observing using 7×50 binoculars from a radiant of RA=128.25°, DECL=+18.6°. During January of 1976, N. W. McLeod, III, indicated surprise that the shower was for real. He described the individual meteors as being “Geminid-like, fairly slow and bright.” During seven hours on January 16/17 and 17/18, McLeod (Florida) detected 12 meteors from this radiant.
During 1977, several observations of this shower were published in Meteor News. On January 15/16, J. West and G. Shearer observed in Bryan, Texas, and saw seven Delta Cancrids in 2 hours 17 minutes, while P. Jones (St. Augustine, Florida) saw two in 2 hours. On January 21/22, McLeod reported observations of six meteors in 4 hours, while F. Martinez (Florida, USA) saw four during the same period. McLeod and Martinez also observed on January 22/23, with the former seeing one meteor in three hours, while the latter saw none in 3 hours and 38 minutes. An analysis of the available observations of 1974, 1975 and 1977, by Gates reveals probable activity levels of 2 to 3 per hour on the night of maximum.
Rates continued to be low into the 1980’s. During 1988 January 15/16 to 24/25, McLeod observed nine Delta Cancrids in 12 hours 55 minutes. During 3 hours on 1983 January 16, Rick Hil (North Carolina) detected two of these meteors. During 1984, M. Zalcik (Edmonton, Alberta, Canada) observed one meteor in one hour on January 13/14, while R. Lunsford (San Diego, California, USA) saw one meteor during five hours on January 4. Finally, during 1986, D. Swann (Dallas, Texas, USA) detected four meteors during three hours on January 11/12 and two meteors during one hour on January 14/15.