Dustin,
A few days ago, after upgrading my MacBook Air to High Sierra, here are the shell commands that I used to install Astrometry-net (v. 0.76_2):
(this, of course, installs the latest Homebrew version)
- brew install netpbm
- brew install cfitsio
- brew install astrometry-net
One then creates a dir 'data' under /usr/local/Cellar/astrometry-net/0.76_2 and put one's index files there. Check your /usr/local/Cellar/astrometry-net/0.76_2/etc/astrometry.cfg.
The shell commands above differ from the ones in the docs just a tad, but they may be of help nevertheless.
Thanks,
Antonio Mario