This ecliptic stream possesses a long duration extending from April 8 to June 16. Maximum occurs during May 18-19 from an average radiant of RA=253°, DECL=-15°. The maximum ZHR is about 2-3, while the radiant diameter is near 3°.
The first observation of this meteor shower was made by H. Corder during May 12-14, 1896. He had plotted five "slow" meteors from a radiant of RA=248°, DECL=-15°.
During 1935 this shower experienced the beginning of recognition as an annual shower when Ronald A. McIntosh listed it in his paper "An Index of Southern Meteor Showers." Designated number 160 and called the "Phi Ophiuchids," this shower was given a duration of May 7-14, with the average radiant being given as RA=248.5°, DECL=-15°.
The publication of Cuno Hoffmeister's Meteorströme during 1948 contained even more support for the Northern May Ophiuchids. Hoffmeister noted a collection of radiants which indicated a radiant of RA=250°, DECL=-18° reaching maximum at a solar longitude of 54 deg (May 15). This radiant was based on seven individual radiants determined by German observers during 1914 to 1937. One of the radiants, designated number 693, was composed of 16 meteors whose intersection indicated a radiant diameter of 3°.
The greatest amount of data to be accumulated on the Northern May Ophiuchids came from the two sessions of the Radio Meteor Project. Z. Sekanina found a duration extending from May 3 to June 4 during the 1961-1965 survey. The date of the nodal passage was determined as May 17.6 (λ=56.2°), at which time the radiant position was RA=252.3°, DECL=-16.9°. During the 1968-1969 survey, Sekanina found a duration of April 8 to June 16. The nodal passage was determined as May 19.0 (λ=57.6°), at which time the radiant was at RA=256.2°, DECL=-12.8°.
The Western Australia Meteor Section has obtained good observations of the shower in recent years. According to the section's director, Jeff Wood, observations conducted in 1979 revealed "Eta Ophiuchids" during May 16-27. A maximum ZHR of 2.46+/-0.56 came on May 19, at which time the radiant was at RA=256°, DECL=-13°.