I looked at my early editon of this atlas and a later one and neither have negative maps included with them. Are the negative maps produced by Sky Publishing in the same way as the positive maps? Perhaps they have been copied from the positive maps by previous owner.When you say you want to research them, what are you wanting to find out?
ps Skelnate Pleso Observatory and its history is absorbing. The details of the people and and observers there is fascinating. Becvar was just one (maybe the most important) but Mrkos, Padjusakova, Kresak , Vovarova and the other comet discoverers and astronomers there were huge characters also.