Known Problems

Known Problems on SkyServer website and the CAS:

There are about 29k scienceprimary spectra in DR4 that do not have the specobjid link in the Photo tables set, so if you do a join on PhotoObj.specobjid, for example, you will not find these spectra. You would have to join on SpecObj.bestobjid to get the spectroscopic and photometric information for these objects. A good way to find them is also to use the SpecPhoto pre-computed join. This problem has been fixed in DR5, the latest public release.
The Sector/Region tables in DR4 have not been populated with the correct data, so they should not be used. These tables have been recomputed for DR5, the latest public release.
The l,b column descriptions in the PhotoAuxAll table Schema Browser entry are switched: l should be longitude and b should be latitude, instead of vice-versa.
Note: This is a documentation error only. The l,b values in the database are in fact longitude and latitude respectively. The documentation error will be fixed in the next update to DR5.
The Schema Browser and Table Descriptions refer to the USNO-B table still but that table has been renamed to ProperMotions in DR5. Please also see the About DR5 page.

Known Problems in SDSS data: Please see the DR4 Known Problems page on sdss.org.