SDSS quick-and-dirty search

You are not a real astronomer if you are not intimidated by the SDSS database.

The main issue is figuring out what to search for: this note is about finding the parameters you want to look for in the database, and passing them to the SQL search engine.

▸ Parameters

The list of all possible parameters and their keyword names within the SDSS catalogue can be found in the Schema Browser.
The SDSS catalogue is organized in tables, each of them containing different parameters.
Some are master tables which include others — for example the PhotoObjAll table encompasses all the photometry parameters.
By expanding the “TABLES” drop-down menu one can access all the tables, and from there the list of parameters within each table.

In case you look for a specific parameter, you might need to use the search function at the top of the page — which surprisingly doesn’t look up for all the keywords within the website (as in 99% of the internet sites!).

SDSS Schema Browser search

SDSS Schema Browser search example.

▸ Do the actual search

In SDSS there are plenty of ways to perform an object search.

In case you have a coordinate list, the best way to go is arguably to use the SQL CrossID (confusingly renamed “Object Crossid” throughout the website).
All you need to do is to specify the table you want  to use and the parameters you want to retrieve (which you have from the procedure above).

The SQL engine will perform a proximity search (which you can tune), but in — the highly improbable — case you have at hand the run, rerun, camCol, field, and obj parameters of your object, you can perform a direct search.
The ideal would of course to search by SDSS ID, but I didn’t figure out yet how to do it in a convenient and simple way (NOTE: keep in  mind that the SDSS IDs have changed since after DR7 because of a new run of object identification). If you know, please share in the comments under this post.

Tips on how to construct SQL searches are provided by the SDSS help page here.

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Posted on July 13, 2018, in Uncategorized. Bookmark the permalink. Leave a comment.

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