查看“ObjID”的源代码

DR7之前和DR8之后的定义方式似乎不太一样

*DR7 之前

: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:
: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