Does anybody know if there is an existing dataset that consists of all known star clusters, their name, and their apparent dimensions or similar? Is it possible to make a query to, or download all SIMBAD objects that are of type "globular cluster"?
Thanks
So far we have about 150ish known globular clusters in the milky way. A list of all the known ones can be found HERE. This includes their locations (may be slightly shifted by now as they were correct as of 2011, the time of writing) and where applicable, the Messier/NGC/IC numbers are included for ease.
Welcome to astro-informatics!
In SIMBAD with "by identifier", using M13 as a working starting point, you find the type contains "Glc", and there is a Glc catalog number, where the catalog designation is a hyperlink -- this takes you to a page where you can get enough info to track down catalogs in Vizier. In this case, an older catalog VII/44 is listed. It has 137 rows. (There is something like 250 GC for the Milky Way).
Knowing the otype, using SIMBAD under "Criteria query" otype="Glc" returns a count of 22831 globulars, not so great. These include those in other galaxies.
TOPCAT http://www.star.bris.ac.uk/~mbt/topcat/ is about the easiest way to get a workable table.
With TOPCAT knowing the catalog is VII/44 ...
...you can File->Load tables ... under the Vizier button; in the "Row Selection" frame, check "all rows" and in the "Catalog Selection" frame choose the "By Keyword" tab. Enter the VII/44 then the "Search Catalog" button. Up pops the catalog; double click the catalog name and you get the catalog downloaded into a sheet-like dialog box.
In general you may get a few things in the Table List frame. Pick the one with the data. (Some have biblio references etc).
With the table data displayed you can re-order the columns by dragging them left/right and put the ra/dec into cols 1 and 2 for ds9 for example.
With the proper table chosen in the main Table List frame -- use File -> Save Tables(s)/Session and save the data. The "Output Format" has CSV -- good enough.
The little icon looks like 4 stacked coins (database) will let you export directly to a PostgreSQL database! that is a different can of worms, but once it works very handy. call the table rawxxxx then select from that to make your internal working table, rename columns, add HEALPix indices as needed (Q3C) etc.
To do this properly, use the SIMBAD ADQL query and join on a table where you can choose GC's out to a distance in kpc. This trims away the galactic ones from the local(ish) ones. You may include the Magellanic clouds for example.
Summary: The SIMBAD web interface is good; Vizier can find catalogs by a general description like globular clusters (which offers you 922 catalogs). TOPCAT is a program you have to install. The SIMBAD ADQL works, but requires a working knowledge of databases using a very restrictive SQL. The tables in TOPCAT differ a bit from the Vizier output, that differ too from ADQL queries.
Older tables have brighter objects suited to actually observing them from the ground.
Note: SIMBAD is not exactly complete in a general sense, check the results.
