The duration of this daylight stream extends over the period of May 4-27. The probable date of maximum activity falls on May 12 (λ=51 deg), at which time the radiant is at RA=13 deg, DECL=+22 deg. The maximum hourly rate is near 8, while the radiant diameter is about 3 deg.
This daylight stream seems to have first been detected by observers at Jodrell Bank (England), as J. A. Clegg, V. A. Hughes and Professor Alfred Charles Bernard Lovell listed a radiant of RA=7 deg, DECL=+20 deg that was detected on May 4, 1947. Although the radar was operated during May 1 to 30, no additional activity from this stream was noted.
The Jodrell Bank equipment again detected this stream on May 12, 1955 (Solar Longitude=50.8 deg). T. W. Davidson found 33 meteors which indicated a radiant of RA=12 deg, DECL=+24 deg and a radiant diameter of 3 deg. The hourly rate was given as 8. The radiant was called the "Upsilon Piscids," and Davidson noted it was near a radiant detected at Jodrell Bank in 1951.
The next radar survey to detect this stream was conducted by B. L. Kashcheyev and V. N. Lebedinets (Kharkov Polytechnical Institute, USSR) in 1960. During the period of May 4-27, 17 meteors were observed. The date of the nodal passage was given as May 12 (λ=52 deg), at which time the radiant was at RA=17 deg, DECL=+19 deg.
The last radio meteor survey to detect the May Piscids was the 1968-1969 session of the Radio Meteor Project. Zdenek Sekanina noted that activity was detected during May 7-9, from an average radiant of RA=11.9 deg, DECL=+19.0 deg. The date of the nodal passage was given as May 8.4 (λ=47.3 deg). The equipment was shut down during May 10-18, so that any extension in the duration of the shower would have been missed.