Objid – Paste in the Object ID for the photo you would like to view. This search is useful when you have a table of objects returned from a SQL query that you want to investigate further.
Ra,dec – You can enter the celestial coordinates in either decimal degrees or sexagesimal (hh:mm:ss for ra and dd:mm:ss for dec) and SDSS will return an image, if one exists. This is a handy search if you are curious about an object that you origianlly started investigating from outside SDSS. Enter the complete coordinates or Explore may not be able to retreive the image.
5-part SDSS – You can use this search to return any image from SDSS regardless of whether or not it is a primary observation. You need to know the run, rerun, camcol, field and object numbers. These numbers refer to the actual image and the location of the version you want to view as it worked its way through the image processing pipeline.
Plate-MJD-Fiber – This search is for locating specific spectra. You need to know the SDSS Spectral Location to use this search.
SpecObjid – Each spectrum that is captured by the SDSS is assigned anobject ID whether or not it is the primary observation or an additional or secondary observation.