Just successfully learned Erekinzil with skills lower than listed on the 'pedia. Here's relevant skills and stats if anyone is curious:

Arcana: 257
Astrology: 245
Scholarship: 182

Disecipline, Wisdom, Intelligence all @ 33

I had AUS up, as well as a quivering astro prediction.

It took a few full rounds of studying, but gosh am I happy to have learned it!