ObjID

DR7之前和DR8之后的定义方式似乎不太一样,以至于SDSS III的skyserver上提供了一个DR7和DR8 match的表，里面分别有DR7和DR8的objID [1]

• DR7 之前[2]

Bits Length (# of bits) Mask Assignment Description

0 1 0x8000000000000000 empty unassigned

1-4 4 0x7800000000000000 skyVersion resolved sky version (0=TARGET, 1=BEST, 2-15=RUNS)

5-15 11 0x07FF000000000000 rerun number of pipeline rerun

16-31 16 0x0000FFFF00000000 run run number

32-34 3 0x00000000E0000000 camcol camera column (1-6)

35 1 0x0000000010000000 firstField is this the first field in segment?

36-47 12 0x000000000FFF0000 field field number within run

48-63 16 0x000000000000FFFF object object number within field

• DR8 The bits are assigned in objid as follows: [3]

63: 0, unassigned

59-62: skyVersion resolved sky version (for DR8 onlyuse 2; 0-15 available)

48-58: rerun, number of pipeline rerun

32-47: run, run number

29-31: camcol, camera column (1-6)

28: 0, unassigned

16-27: field, field number within run

0-15: id, object number within field