The catalog web service allows you to submit a query, both through an online form and programmatically. You can access the Guide Star Catalog(s) as well as a number of other catalogs available from MAST.

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These web forms were built on a publicly accessible API, which you can use to perform your own queries.


The API endpoint is:

To perform a query, you'll need to fill in the Parameters with your desired search criteria.

Quotation Marks

Do not place quotes around any of the parameter values, or your query will fail. Additionally, the parameters are both case-insensitive and order-insensitive.

Required Parameters for each search type

At a minimum, you must create a query in the style of one of the four following:

Search Type

Required Parameters

Example (using optional parameter defaults :  CATALOG=GSC30, FORMAT=VOTABLE)
VO Cone SearchRA=ra(deg) &DEC=dec(deg) &SR=search radius(deg)
Box SearchBBOX=raMin(deg), decMin(deg), raMax(deg), decMax(deg), 20, 10.5, 21
STCS Search

STCS=Space Time Coordinate System shape (CIRCLE or POLYGON)

Note that a STCS=CIRCLE is the same as a VO ConeSearch 83.633083 -22.0145 0.01 180.428742 -18.893042 180.455582 -18.906816 180.488081 -18.858382 180.461245 -18.84461 180.428742 -18.893042 
ID SearchID=catID

You do not need to include these parameters in your search, but you can use them you further filter your results. Some options, like filename and format, alter the results returned to you.

Optional Parameters


CATALOG=code (Default if omitted is GSC30)

For clarity this is a recommended parameter. It WILL change as newer versions of GSC are released,20,10.5,21&format=csv

EPOCH=yyyy.y (Updates ra/dec using proper motion and parallax IF AVAILABLE in catalog)

original query:

query with updated coordinates:


Note: TEXT is only supported for GSC1, GSC2 and HLA catalogs for backwards compatibility with other services and is NOT recommended

FILENAME=outputname (directs output to file)

MAXOBJ=n (limits number of entries returned by brightest magnitude)

original query: 
query limited to 10 objects:

MAGRANGE=bright,faint (limits number of entries returned by limits)

original query: 

query limited to specified magnitude range:,17.2 

MINDET=n (minimum number of detections PanSTARRS only)

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