THE GREAT STAR MAP 561 



No very great surprise therefore was felt when one or two of 

 the new plates were found to be faulty from a different reason. 

 There was no further failure in sensitiveness, for the plate- 

 makers were most sympathetic about our disappointment and 

 immediately furnished an excellent batch of new plates. The 

 fault was now that the telescope had not been accurately pointed 

 to the right region of the sky — a kind of mistake which might 

 reasonably be ascribed to the strain of working against time. 

 But it is a good rule in astronomical work (probably also in 

 other walks of life) to get to the bottom of any mistake if 

 possible and so it proved in this instance. On comparing one 

 of the wrongly set plates with another of the same region, it 

 was seen that it contained a strange object which ultimately 

 proved to be a New Star. The mistake had arisen because it 

 is customary to select as guiding star the brightest in the 

 neighbourhood (as being most easily identified) and the new 

 star had blazed up so as to be brighter than any other near it ; 

 so that Mr. Bellamy had accepted it without question as the 

 one to which he was to point his guiding telescope during the 

 taking of the photograph. 



We could not be sure for some little time of the nature of 

 this object. It might be a planet or a variable star. The first 

 alternative was soon disposed of, because it is easy to look up 

 the places of the planets which could be bright enough ; and, 

 moreover, a planet would probably have betrayed itself by a 

 slight movement between the three exposures given to each 

 plate in the making of the map. The second alternative occu- 

 pied attention rather longer. There are many stars scattered 

 over the sky whose brightness varies considerably, so that they 

 might at one time show an emphatic image on one plate and 

 at another time be too faint to affect the plate at all. Many of 

 these are well known and can be found in catalogues already 

 published ; others are being discovered year by year and no 

 doubt we are still unaware of many to be discovered in the 

 future. During the afternoon the lists were searched without 

 finding any mention of a variable in that particular neighbour- 

 hood ; and when in the evening the star was found to be still 

 shining in the exact place of the photograph, telegrams were 

 sent to other observers inviting their attention to it as probably 

 a New Star. Any remaining doubts were dispelled by the 

 spectroscopic observations and Nova Geminorum took its place 



37 



