Discovery
The Vatican Observatory (Italy) was one of the participants in the Carte du Ciel and was responsible for measuring all stars within the zone between declination +55° and +64°. For over 25 years, Father Giuseppe Lais was the primary person at the observatory who was responsible for photographing the sky with the 33-cm refractor and developing the plates. During March of 1918, Father J. G. Hagen, the director of the observatory, sent a letter to the Astronomische Nachrichten giving the positions of a comet that was found by Lais on three plates exposed on 1917 July 12, 13, and August 20. Hagen said the comet was probably about magnitude 8 or brighter and exhibited a tail extending 8 arc minutes toward the northwest. He added that there was no doubt the images were of real comets and not plate defects or reflections, but that all three images may not be of the same comet. Hagen said the July plates were catalog plates and of short exposure, while the August plate had three successive exposures of 40 minutes or more. The 1918 February issue of The Observatory had published some of the above information, as well as initial rough positions; however, it added that a request had been sent to Harvard to see if any of their plates showed this comet.
Positions
Analysis
A. C. D. Crommelin discussed these images in the 1918 March issue of The Observatory. First, he noted that Lais had requested other observers to check plates taken within the Draco or Cygnus regions during the summer of 1917 for possible images of these objects. Crommelin also stresses that the images must refer to more than one comet "since it appears to me certain, from an investigation by graphical method, that the August object cannot be the same as the July one...." But he also sheds some doubt on the objects. Crommelin wrote, "I cannot help suspecting that all three images may arise from some terrestrial cause, especially as I learn that the August object shows no sign of trailing on the plate, though the exposure was a long one." Crommelin threw even more doubt on the images in the 1918 April issue of The Observatory. He said that Hagen had sent him paper prints of the plates. Crommelin commented, "Inspection of them shows that, though there were 3 exposures on each plate, the objects in question do not show multiple images. Moreover, the tail on Aug. 20 points exactly towards the Sun." Finally, Crommelin adds, "Plates taken at Harvard near the same dates do not reveal any doubtful images comparable with these in brightness. A verdict of "Not proven" therefore seems justified."
Sources:
The Observatory, 41 (1918 Feb.), p. 113
The Observatory, 41 (1918 Mar.), p. 145
The Observatory, 41 (1918 Apr.), p. 184
Astronomische Nachrichten, 206 (1918 May 3), p. 179
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