Iain Robb, 47, told one of his victims that he had a thing for “hot academic women.”
Robb forwarded numerous images of a naked man on social media in September and October 2021.
He sent them from his home in Rutherglen to the historians he did not know.
Robb pleaded guilty at Glasgow Sheriff Court to three charges of sending written sexual communication.
Sheriff Paul Reid put Robb on the sex offenders register for 10 years as well as the jail sentence, The court heard the first victim received a message request on Facebook messenger on September 3
Robb using the name “Jonathan Roberts” sent numerous sexual and graphic images to her.
Prosecutor Emma Baker said: “These were of a naked male in various positions, exposing himself and performing a sex act.
“There were a total of 44 images sent.
“There was also a highly sexualised message, stating how attractive he found the woman and how he had a thing for hot academic women.”
The woman found the images “highly disturbing” and she blocked Robb before contacting the police.
A second woman also received 44 images from Robb on Facebook messenger posing as Jonathan Roberts.
Miss Baker said that the images were of a man who was on a bed exposing himself.
The third victim received images that were “sexually explicit in nature” from Jonathan Roberts.
Pictures of the man’s face were also included in some of the files sent.
Miss Baker said: “All three victims are historians – two are university lecturers and one is an author.
“All three know each other and once the first woman disclosed what she received, all three realised they had received the same message and images from the same man who was not known to them.
“The first woman passed the details of the other two victims to the police.”
An investigation showed that the images were sent from Robb’s IP address and he was arrested.
Robb’s previous convictions include sending a naked image of himself on Facebook to a women he went to school with.