In the index filenames, the convention is that the "52" means the "5200-series", and the next two digits are the scale, going from 00 to 19, where 00 contains features from 2 to 2.8 arcminutes in diameter. That's just about the limit for what existing astrometric catalogs can support. But we can push it a bit and go to "M1" (minus 1), with features 1.4 to 2 arcminutes. Those are useful for solving JWST images. I've only created a subset of those (probably corresponding to the places on the sky of the first few images from JWST!).