typos
Merge branch 'master' of github.com:davidwhogg/SloanAtlas
more intro text
introduction done (zeroth draft level)
Tractor mention in intro
sdss imaging data
typo
PSF
Terse description of the Tractor's linearization + line-search optimization; some wordsmithing
add tycho-2 citation
notes to team
control-M insanity, notes to team
notes to dstn
resolved Ekta conflict