| Type | Explanations |
| AMC | Candidate Am CVn variables (ancillary target) |
| BLAZGRFLAT | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: within 2" of a CRATES radio source and within a Fermi error ellipse (ancillary target) |
| BLAZGRQSO | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: within 2" of a FIRST radio source and within Fermi error ellipses (ancillary target) |
| BLAZGVAR | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: miscellaneous candidate blazars (ancillary target) |
| BLAZGX | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: within the Fermi error ellipses and within 1' of a RASS X-ray source (ancillary target) |
| BLAZGXQSO | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: within 1' of ROSAT source and within Fermi error ellipses (ancillary target) |
| BLAZGXR | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: within 1' of ROSAT source and within 2' of a FIRST radio source. (ancillary target) |
| BLAZR | miscellaneous candidate blazars (ancillary target) |
| BLAZXR | Candidate optical counterparts of sources detected by γ-ray Fermi telescope: plausible Fermi sources (ancillary target) |
| BLAZXRSAM | miscellaneous candidate blazars (ancillary target) |
| BLUE_RADIO | radio galaxies with blue colors at z>0.3 (ancillary target) |
| BRIGHTGAL | |
| CHANDRAv1 | Optical counterparts of Chandra X-ray targets (ancillary target) |
| CXOBRIGHT | Remarkable X-ray sources that have bright 2-8 keV fluxes (ancillary target) |
| CXOGRIZ | Remarkable X-ray sources that have "outlier" SDSS colors (g-r)>1.2 or r-i>1.0 or i-z>1.4. (ancillary target) |
| CXORED | Remarkable X-ray sources with red SDSS colors of (g-i)>1.0 (ancillary target) |
| ELG | Luminous Blue Galaxies (ancillary target) |
| FBQSBAL | Broad absorption line (BAL) quasar with spectrum from the FIRST Bright Quasar Survey (FBQS) (Cat. J/AJ/112/407 J/ApJS/126/133, J/ApJS/135/227) (ancillary target) |
| FLARE1 | Flaring M stars (year 1 targets) (ancillary target) |
| FLARE2 | Flaring M stars (year 2 targets) (ancillary target) |
| GALAXY | galaxy |
| GAL_NEAR_QSO | galaxy that lies between 0.006' and 1' of the line-of-sight for a spectroscopically-confirmed quasar (ancillary target) |
| HIZQSO82 | Quasar candidate selected with UKIDSS YJHK photometry (ancillary target) |
| HIZQSOIR | Quasar candidate in SDSS Stripe 82, selected with UKIDSS YJHK photometry (ancillary target) |
| HOT_STD | Hot standard |
| HPM | High Proper Motion stars (ancillary target) |
| KQSO_BOSS | Quasars selected from UKIDSS photometry (ancillary target) |
| LBQSBAL | Broad absorption line (BAL) quasar with spectrum from the Large Bright Quasar Survey (LBQS) (Cat. J/A+A/358/77 J/AJ/109/1498, J/AJ/122/518 (ancillary target) |
| LOW_MET | Low-metallicity M dwarfs (ancillary target) |
| LRG | Luminous Red Galaxy |
| MTEMP | Template M-stars observed as a comparison sample (ancillary target) |
| NA | (not applicable) |
| NONLEGACY | (non-legacy observation) |
| ODDBAL | Broad absorption line (BAL) quasar with various unusual properties (ancillary target) |
| OTBAL | Photometrically-selected overlapping-trough (OT) broad absorption line (BAL) quasar (ancillary target) |
| PREVBAL | Broad absorption line (BAL) quasar with prior spectrum from SDSS-I/-II (ancillary target) |
| QA | Quality assurance target |
| QSO | Quasi-stellar object |
| QSO_AAL | Radio-quiet, with one absorption system associated with the quasar (ancillary target) |
| QSO_AALs | Radio-quiet, with multiple absorption systems associated with the quasar (ancillary target) |
| QSO_GRI | Quasar candidate selected in gri color space (ancillary target) |
| QSO_HIZ | Quasar candidate detected only in SDSS i and z filters (ancillary target) |
| QSO_IAL | Radio-quiet, with one intervening absorption system (ancillary target) |
| QSO_RADIO | Radio-loud, with multiple absorption systems, either local or intervening (ancillary target) |
| QSO_RADIO_AAL | Radio-loud, with one absorption system associated with the quasar (ancillary target) |
| QSO_RADIO_IAL | Radio loud, with one intervening absorption system (ancillary target) |
| QSO_RIZ | Quasar candidate selected in riz color space (ancillary target) |
| QSO_SUPPZ | Known quasar with redhift 1.8<=z<=2.15 |
| QSO_VAR | Likely quasar selected by " No Quasar Left Behind" program (ancillary target) |
| QSO_VAR_FPG | Quasars selected by variability (ancillary target) |
| QSO_VAR_SDSS | Quasar defined in VARQSO description |
| QSO_noAALs | Radio-quiet, with multiple intervening absorption systems and no associated absorption systems (ancillary target) |
| RADIO_2LOBE_QSO | Object near the midpoint of a double-lobed object identified in FIRST (ancillary target) |
| REDDEN_STD | Reddening standard star |
| RED_KG | Red giants in the outer halo of the Milky Way (ancillary target) |
| ROSAT_D | ROSAT match, bright enough for SDSS spectroscopy |
| RQSS_SF | Red QSO selected from SDSS and FIRST photometry (ancillary target) |
| RQSS_SFC | Red QSO selected from SDSS and FIRST photometry (child object in SDSS imaging) (ancillary target) |
| RQSS_STM | Red QSO selected from SDSS and 2MASS photometry (ancillary target) |
| RQSS_STMC | Red QSO selected from SDSS and 2MASS photometry (child object in SDSS imaging) (ancillary target) |
| RVTEST | stars previously observed spectroscopically as a test of the reproducibility of velocity measurements (ancillary target) |
| SERENDIPITY_BLUE | Serendipity Blue target (SEGUE target) |
| SERENDIPITY_DISTANT | Serendipity Distant target (SEGUE target) |
| SERENDIPITY_FIRST | Serendipity FIRST target (FIRST radio source within 1.5'') (SEGUE target) |
| SERENDIPITY_MANUAL | Manual serendipity flag set |
| SERENDIPITY_RED | Serendipity red target (SEGUE target) |
| SKY | |
| SN_GAL1 | Fiber assigned to the galaxy nearest the supernova position (ancillary target) |
| SN_GAL2 | Fiber assigned to second-nearest galaxy (ancillary target) |
| SN_GAL3 | Fiber assigned to third-nearest galaxy (ancillary target) |
| SN_LOC | Fiber assigned to position of original supernova (ancillary target) |
| SPECTROPHOTO_STD | |
| SPEC_SN | Target selected from spectroscopy instead of photometric variation (ancillary target) |
| SPOKE | Widely-separated binary systems in which both stars are low-mass (spectral class M) (ancillary target) |
| STANDARD | standard |
| STAR | stellar target |
| STAR_BHB | Blue Horizontal-branch star (SEGUE target) |
| STAR_BROWN_DWARF | Brown dwarf (SEGUE target) |
| STAR_CARBON | Carbon star (SEGUE target) |
| STAR_CATY_VAR | Cataclysmic variable (SEGUE target) |
| STAR_PN | Central stars of planetary nebula (SEGUE target) |
| STAR_RED_DWARF | (SEGUE target) |
| STAR_SUB_DWARF | (SEGUE target) |
| STAR_WHITE_DWARF | (SEGUE target) |
| STD | |
| STRIPE82BCG | Brightest cluster galaxy in stripe 82 survey area (ancillary target) |
| TEMPLATE_GAL_PHOTO | Galaxy template |
| TEMPLATE_QSO_SDSS1 | Quasar template |
| TEMPLATE_STAR_PHOTO | Stellar template |
| TEMPLATE_STAR_SPECTRO | Stellar template (spectroscopically known) |
| VARBAL | Photometrically-selected candidate broad absorption line (BAL) quasar (ancillary target) |
| VARS | Variables outside the stellar and quasar loci (ancillary target) |
| WHITEDWARF_NEW | White dwarf candidate whose spectrum had not been observed previously by the SDSS (ancillary target) |
| WHITEDWARF_SDSS | White dwarf candidate with a pre-existing SDSS spectrum (ancillary target) |
| XMMBRIGHT | Remarkable X-ray sources that have bright 2-12keV fluxes (ancillary target) |
| XMMGRIZ | Remarkable X-ray sources that have "outlier" SDSS colors (g-r)>1.2 or r-i>1.0 or i-z>1.4. (ancillary target) |
| XMMHR | Remarkable X-ray sources that have unusual hardness ratios in the HR2-HR3 plane (ancillary target) |
| XMMRED | Remarkable X-ray sources with red SDSS colors of (g-i)>1.0 (ancillary target) |
| brighterL | Bright L dwarf candidates (ancillary target) |
| brighterM | Bright M dwarf candidates (ancillary target) |
| fainterL | Faint L dwarf candidates (ancillary target) |
| fainterM | Faint M dwarf candidates (ancillary target) |