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# IAU designations

The official SDSS designation for an object is

SDSS JHHMMSS.ss+DDMMSS.s

where the coordinates are truncated, not rounded. This format must be used at least once for every object listed in a paper using SDSS data.

When abbreviating the object name in the text please use the "J" to indicate the equinox of the coordinates. For example

SDSS J123456.89-012345.6

could be abbreviated as

SDSSJ1234
SDSSJ1234-0123

Please refer to the CDS dictionary on SDSS for further information.

## Why bother?

The following is an excerpt from a message by Helene Dickel, the Chair of the IAU Working Group Designations.

To illustrate the kind of confusion that shortened names can lead to, consider the source in the Fan et al. paper in ApJ 526, L57, 1999 properly designated SDSSp J153259.96-003944.1 which is then referred to as SDSS 1533-00 for brevity. Not only is there no J but the RA has been rounded instead of truncated. Without the explicit J, one may assume these are B1950 coordinates. If a subsequent author only gives the shortened name, then a reader searching in NED with IAU format on 1533-00, assuming B1950 coordinates, specifying acronym SDSS but nothing for the object type, would be given 243 objects that might be the one in question. Most begin with J2000 RA of 1533, 1534, or 1535. You can narrow the choices if you realize that SDSS source names are based on J2000 coordinates and that this source is a QSO. Then there are 9 choices which include SDSS J153306.42+000635.1 and SDSSp J153259.96-003944.1 Searching for SDSS 1532-0039 assuming J2000 coordinates and QSO yields two choices SDSS J153243.67-004342.5 and SDSSp J153259.96-003944.1 However, if you think SDSS 1532-0039 uses B1950 coordinates and don't specify a QSO, you are given 11 possibilities which start with RA 1534 or 1535 and Dec mostly start with 004, NONE of which include the relevant source SDSSp J153259.96-003944.1!

It is not just the earlier papers that give shortened names without the J. A recent paper in AJ gives SDSSHHMM+DDMM with no full coordinates and a website as the reference. It took over 2 hours with the help of NED to track down the original SDSSp designations and references for those three SDSS sources plus several other sources whose designations were equally corrupted. Following discussions with the Editor and Author, an Addendum is being published which includes a table giving the short name, the official SDSS or SDSSp full designation (and the full designation of the other sources), precise J2000 coordinates, and the published reference for each source. Editors and journal readers would appreciate having this information already available when you publish your papers.