Z. M. Pereyra (Cordoba Observatory) discovered this comet on 1963 September 14.39 in the constellation Hydra. He described the comet as magnitude 2, with a centrally condensed coma, and exhibiting a tail more than 1 degree long. The comet was confirmed by McClure (Hollywood, California) on September 16.5. He estimated the magnitude as 6 and said a faint, straight tail extended 10.5 degrees toward the west. This tail was narrow at the coma, but widened to 0.75 degree at the end. The coma was described as "relatively small with sharp central condensation."
The comet was widely observed in the Southern Hemisphere by September 17. The comet's brightness was consistently estimated as between 6 and 6.5. The largest reported visual tail length was 3 degrees, while photographs by Harvard College Observatory's survey stations in South Africa and Australia showed the tail between 6 and 10 degrees long. Descriptions by Stephanus C. Venter (South Africa) on that date indicated the comet's head was small and irregular and he surmised that he was only seeing the central condensation because of the comet's low altitude. He added that no nucleus was visible and the tail fanned slightly towards the end.
Venter's thought that only the comet's condensation was being seen at low altitude seemed proven during the next few days. From the September 18th through the 21st Southern Hemisphere observers continued to estimate the comet's brightness as between magnitude 6 and 6.5. One of the faintest magnitudes during that period was a magnitude 7 by Giclas (Lowell Observatory, Arizona) on the 19th, but this Northern Hemisphere observer was seeing the comet at a very low altitude. Another Northern Hemisphere observer, de Vaucouleurs (McDonald Observatory), saw the comet on the 20th. Even though he estimated the magnitude of the head as 6.0 at low altitude, he suggested the integrated magnitude might have been near 3. De Vaucouleurs said no definite nucleus was seen and added that the central condensation was 2 to 3 arcmin across. Through binoculars he estimated the coma was 15 arc minutes across. On the 18th Venter said the comet's head was starlike and displayed a narrow tail 6 degrees long. C. Capen (Wrightwood, California) estimated the tail length as 18 degrees on the 21st.
Observations during the last nine days of September indicated the comet was steadily fading. Observers seeing the comet prior on the 21st and earlier, were reporting magnitudes between 6.5 and 7 on the 22nd and between 7 and 7.5 by the 30th. Although Capen again reported a tail 18 degrees long on the 22nd, continued visual observations by Venter and others indicated the tail was only 5 or 6 degrees long on the same date. Venter's continued observations indicated the tail was nearly invisible on the 24th, although nearly 1.5 degrees could still be made out, while on the 25th it was "very, very faint" and only 1 degree long. Various observers reported tail lengths of 0.5 to 2 degrees on the 27th and about 1 degree long by the 29th. Venter said the central condensation was located towards the extreme southwestern edge of the comet on the 22nd and was estimated as magnitude 7.0. He noted that during the next several days it became more diffuse and irregular. Also during this period the comet came under observation at several addition Northern Hemisphere observatories in the United States, Japan, and Czechoslovakia.
As October began magnitude estimates mostly fell within the range of 7.5 to 8. The comet's continued fading caused a decline in observations as the month progressed and only a few days after reaching magnitude 9 on the 14th the South African observers Venter and J. C. Bennett, who had followed the comet faithfully since September 17, could no longer see the comet. Venter's unusually long tail length estimate of 4 degrees on October 1 was the last reported tail length by any observer and Bennett's coma diameter estimate of 3 arcmin on the 15th was the last visual size estimate of this feature.
The comet became a photographic object after mid-October, which meant the comet's total magnitude appeared to have dropped suddenly. In reality, however, this was only because photographs tended to be just long enough to detect the comet's central condensation for position measurements. Freimut Börngen (Karl-Schwarzschild Observatory, Tautenburg) photographed the comet on October 23 and estimated the magnitude as 14. He also said the coma was 20 arcsec across and was diffuse, with a condensation. On October 31, Bšrngen failed to detect the comet on two photographic exposures.
The comet had faded enough by November so that only two observers were able to continue observations. Elizabeth Roemer (U. S. Naval Observatory, Flagstaff) photographed the comet on November 9 and revealed a nucleus of magnitude 17.2, as well as a faint tail. Interestingly, she said there was a possible secondary nucleus 0.1 arc minute away. Although this marked the only date this secondary nucleus was seen, many astronomers consider it to have been real. The other astronomer who was able to continue observations into November was Tomita (Dodaira, Japan). He was able to photograph the comet on both November 16 and 26.
Roemer obtained the final two observations of the comet. Photographed on December 14 and 18, the comet's nucleus had faded to magnitude 18.2 by the latter date.
The first orbit was published on September 30. Michael McCants used 8 positions obtained during the period of Septmber 14 to 23 and computed a parabolic orbit with a perihelion date of 1963 August 31.88, a perihelion distance of 0.112 AU, and an inclination of 40.2°. Some of these positions were not of the highest quality so the orbit was only considered a good starting point to help acquire further observations as the comet faded. M. P. Candy published his orbit on October 3. Using positions acquired during the period of September 17 to 25 he determined the perihelion date as August 23.39, the perihelion distance as 0.007 AU, and the inclination as 143.7°. On October 7, Leland E. Cunningham (Leuschner Observatory, Berkeley) published a parabolic orbit giving the perihelion date as August 23.90, the perihelion distance as 0.005 AU, and the inclination as 144.5°. Cunningham said the comet was "a member of the group of spectacular comets that almost graze the surface of the sun." He added that the orbit was "almost identical" to comets seen in 1668, 1843, 1880, and 1882.
Once all observations were available, astronomers realized this comet was moving in an elliptical orbit. Zdenek Sekanina (People's Observatory, Prague) computed the first elliptical orbit during April 1964 which indicated an orbital period of about 1100 years. During January 1967, Sekanina revised his orbit and found an orbital period of 861±16 years. B. G. Marsden conducted a new investigation of the sungrazing family of comets in 1978. His orbit for comet Pereyra indicated an orbital period of 903 years.