Abstract :
This paper examines the interrelations between astronomical images of nebulae and
their observation. In particular, using the case of the ‘Great Spiral’ (M51), we follow this
nebula beginning with its discovery and first sketch made by the third Earl of Rosse in 1845, to
giving an account, using archival sources, of exactly how other images of the same object were
produced over the years and stabilized within the record books of the Rosse project. It will be
found that a particular ‘procedure’ was employed using ‘working images’ that interacted with
descriptions, other images and the telescopic object itself. This stabilized not only some set of
standard images of the object, but also a very potent conception of spirality as well, i.e. as a
‘normal form’. Finally, two cases will be contrasted, one being George Bond’s application of
this spiral conception to the nebula in Orion, and the other Wilhelm Tempel’s rejection of the
spiral form in M51.
