Target Name
The name of the astronomical object you want to search for. Examples of valid names include gam Gem, NGC 1068, JUPITER, and hd 45677. Multiple target names can be entered if separated by commas, although table sorting is turned off in these cases.

The Target Name is used in combination with the Resolver Field. If the SIMBAD, CFA (SIMBAD at CfA), NED (default) or HLA name resolver options are chosen, then coordinates returned from these services are used to perform a cone search with the specified search radius.

You do NOT have to use the resolver. Choose the "Don't resolve" option to perform string searches on the object name in the database.

When you search on the object name in the database (i.e. without using the name resolver), case will be ignored. The object name will not be wildcarded at the front and back automatically (that's so if you innocently enter IO, you don't match things like ORION). You can however wildcard the object name using * (for example, *IO*). You can also enter a comma-separated list; for example, *JUP*,*SAT* would match object names containing either JUP or SAT. Note that most, if not all, missions store target names in a format that is not always compatible with the NED or SIMBAD name resolvers.

Resolver
This field describes how trget names are to be handled. If you want to resolve a target name into its coordinates (the default), this field ican be used to describe which name resolver to use. You can also elect to search the database by the target name itself by choossing the "Don't resolve" option.

The two main name resolver services are SIMBAD and NED. NED is the NASA Extragalactic Database at Caltech in Pasadena, California, and SIMBAD is the Set of Identifications, Measurements, and Bibliography for Astronomical Data at the Centre de Données astronomiques in Strasbourg, France (SIMBAD at CDS). A mirror site at the Center for Astrophysics in Boston is also now available and is denoted as "SIMBAD at CFA". NED is an extragalactic database, and generally won't resolve object names within the Milky Way galaxy.

Because we occasionally have problems with network connections and web servers, we now store previously resolved target names and coordinates in our own local database and search this database before trying to access the other name resolvers using various web services. By default, If no entry is found in the local cache, the entered object names will first be sent to the NED service, and, if still not found, then CFA, CDS, and HLA in that order. You may also go directly to CFA, CDS, or HLA by changing the selected name resolver, although the local cache is always checked first.

If any error occurs, the search form will be redrawn with an error message at the top. Otherwise, the returned coordinates will then be used to search the database, along with whatever other query qualifications you have given.

We recommend that you use object name resolution to find observations of specific stationary targets. This is the most reliable way to look up observations, because the observer could have given any object name at all (for example, NGC1976 instead of M42, or PARALLEL-FIELD).

The SIMBAD and NED name resolvers can resolve only fixed objects; they cannot compute the positions of moving objects (planets, comets, etc.). To find moving objects, try selecting the appropriate category option available on most MAST search forms, or as mentioned above, enter an object name that could match what you're looking for, and select "Don't resolve" for the name resolver. Note wild cards are allowed, so for Jupiter you might enter "*JUP*".

Right Ascension, Declination
The Right Ascension and Declination values. If single values are entered, a cone search is performed using the specified search radius (default = 3 arcminutes).

You may also enter ranges of right ascension or declination, using the ".." operator. For example, you can enter 21h 51m .. 21h 52m for the right ascension, and 28 51 .. 29 51 for the declination. Comparators can also be used, i.e. ">", ">=", "<", "<=". For example, "> 85" as a declination value will return all observations with declination larger than 85 degrees. (Note when ranges of coordinates are specified the search radius will be ignored. Also, searches on ranges can be quite time consuming.)

Coordinate values may be specified using a number of formats. Examples of accepted values include: 

    Decimal Degrees
       	185.63325 29.8959861111111
 
    Hours, minutes and Seconds
        12 22 31.98      29 53 45.55
        12h22m31.98s     29d53m45.55s
        12:22:31.98     +29:53:45.55
        12h22'31.98"     29d53'45.55"
        12h 22m 31.98s   29d 53m 45.55s
        12h 22' 31.98"   29d 53' 45.55"
        12h 22' 31.98"  -29d 53' 45.55"
        12h22'31".98    -29d53'45".55
        12h22m31s.98    -29o53m45s.55
        12h 22' 31".98  -29d 53' 45".55
     
    Hours/Degrees and Minutes (no seconds)
        12 22     29 53
        12h22m   +29d53m
        12h22m    29d53m
        12:22m    29:53m
        12h22'    29d53'
        12h 22m   29d 53m
        12h 22'   29d 53'
        12h 22'  -29d 53'

    The RA may be given in decimal degrees by indicating
    a D or d after the degrees:
        12d 22m   29d 53m
Spacing is not important, as long as the value is unambiguous. You can delimit the hours/degrees, minutes, and (optional) seconds with letters, colons, spaces, or any character that's not a digit or a decimal point. Like target names, multiple coordinates can be entered if separated by commas.

Radius
The radius of the search box around the RA and Dec, in floating-point arcminutes (e.g., 5.0). You should be careful about giving too restrictive a search radius since (for some missions) the coordinates of the object were given by the Guest Observer, and may not reflect the precise pointing of the instrument at the time of the observation.

The search routine computes the angular separation between each result dataset and the search center so this really is a circular radius. (Results are generally sorted on the angular separation by default.) Note a range may also be specified so, for example, to search for all observations between 2 and 8 arcminutes from the center of a galaxy, just enter 2 .. 8 for the radius.

Equinox
The equinox of the RA and Dec you have entered, either B1950 or J2000. (Note: currently only J2000 is allowed as input.) This only applies to the input coordinates. The coordinates displayed in the search results will depend on the mission database and the selected output columns. (Note: all MAST missions include J2000 coordinates as default output columns.)

If you enter a target name and use either the SIMBAD or NED name resolver, the equinox will be set to J2000.