Yes, the first comet photos, by Underwood and Bond, were of C/1858 L1 (Donati) in 1858. With the help of Mike Maunder we estimated that these would have been taken using Collodion plates that had a sensitivity of around 0.05 to 0.1 ISO . By the time of Lockyer’s attempts in 1874 he would have been using gelatine plates with a sensitivity of maybe 0.2 ISO. No wonder it was so hard to photograph a comet but even then people knew to use short, fast lenses. Did Lockyer try any photography using a portrait lens? Eight years later, in 1882, Gill got his famous photo of C/1882 R1 which led to the Cart du Ciel project.