I just left a note about procuring source materials on your talk page    Also with reference to your mention of Cassinis tables you might like to notice that the practice about signs in the eighteenthcentury tables was to treat a sign as just a superior unit of  degrees  this is shown by the presence of this unit also in the tables of increments corresponding to periods of time and in the tables of angular differences such as mean anomaly these usages show that such a sign did not need to begin at any particular place it was just any arc of  degrees a practice also mentioned as occasionally occurring in ancient times I think by O Neugebauer in History of Ancient Mathematical Astronomy