BDA contains cross-reference tables which provide the cross-identifications between many numbering systems. Information may be retrieved in both senses: either from the original numbering systems to that adopted in BDA or from BDA's system to any other one.
If you are not in the directory of NGC 129, enter:
> ngc 0129
> tab -r list the references of the numbering systems included in the cross-reference table.
> tab list the cross-reference table.
> tab 16 20 30 display the line for stars 16 20 and 30.
> tab -r 4 remind you of the reference corresponding to column 4.
> tab -l 3 select the entries corresponding to column 3.
> tab -s 3 extract couples of cross-identifications: BDA number - column 3 number, sorted by column order.
> tab -i print the references and the cross-reference table.
> tab -c start a cross-identification program in the reverse sense: from any column to the adopted system.
Give the reference number: 0
(0 displays the reference list, when you need it.)
Give the reference number: 2
Which star? 5
Another star? 10
Another star? -1
Give the reference number: 3
Which star? 20
Another star? 0
The entry "-1" allows to change the reference searched, here one moves from reference 2 to 3.
> tab -s produce an output sorted according to the selected column. May be redirected to any file.
sort on which column? 2
Special numbering systems may also be interrogated:
> ngc 0457
> tab -k 22- 75 look for "22- 75" in the table