Secondary target mask bits in SDSS-I, -II (for LEGACY_TARGET2, SEGUE1_TARGET2, SEGUE2_TARGET2, SPECIAL_TARGET2 or SECTARGET).

Bit name	Binary digit	Description
LIGHT_TRAP	0	hole drilled for bright star, to avoid scattered light
REDDEN_STD	1	reddening standard star
TEST_TARGET	2	a test target
QA	3	quality assurance target
SKY	4	sky target
SPECTROPHOTO_STD	5	spectrophotometry standard (typically an F-star)
GUIDE_STAR	6	guide star hole
BUNDLE_HOLE	7	fiber bundle hole
QUALITY_HOLE	8	hole drilled for plate shop quality measurements
HOT_STD	9	hot standard star
SOUTHERN_SURVEY	31	a segue or southern survey target