Hoskins has done a book and a couple of papers on Iberian tomb alignments which iirc showed a cluster around 99 degrees . Henshall commented ,after covering all the Scotish tombs that few exhibited astro alignmnets although there were some regional groups that had different preferences for orienatation. Mereaux in Brittany has argued that the majority of dolmens there are aligned in the same direction of the underlyong geological fault , he then spoils by suggesting that they are an early warning system for earthquakes , the capstone wobbling when it's time to get your auroch and head towards Paris .What you would need for your database is the latitude of the monument then fron that you can work out the important solar and lunar events e.g. solstices , major standstills , cross quarter days and minor standstills also get considered but notice should be taken of any alignmnet as it may fit into a category that we don't as yet consider significant .