Astronomical Server URL

Special case: Query by position

There are two possible equivalent syntaxes ...

(the -c.rm can itself be decomposed into -c.rm.min and -c.rm.max; the same structure decomposition can be applied for the -c.bm parameter)

where:

• coordinate/name:
  • specification of the target position as -c= either in decimal degrees, or in standard sexagesimal: The sign (- or +, or the %2b HTML-coded equivalent of the '+' sign) separates the RA from the Dec part. Sexagesimal notation must contain ":" (or the %20 HTML-coded equivalent of the blank, but NOT the + HTML equivalent of the blank!) as separator between HH, MM and SS.s (ex: 12:34:23.2). If neither ":" nor "%20" exists, the position is assumed to be in decimal degrees. In particular, specifying a position like 1232+435 is currently not supported.
  • specification of the target name (object) as -c=
  Note: the distinction between name and actual position is done by searching the presence of an alphabetical symbol (lowercase or uppercase letter)
• equinox: specification of the equinox as eq= subparameter (or -c.eq parameter):
  eq=Jyyyy[.fraction] or JDjulian_date[.fraction] for FK5-based,
  eq=Byyyy[.fraction] for FK4-based,
  eq=Eyyyy[.fraction] or EJDjulian_date[.fraction] for ecliptic,
  eq=G for Galactic,
  eq=S for supergalactic;
  The default is J2000.0
• epoch: specification of the epoch as
  ep=yyyy[.fraction] in Julian years, or
  ep=JDjulian_date[.fraction]
  ep=now would designate the current date

  Note: if only one of (equinox, epoch) is specified, the two parameters are assumed to be identical.

• radius: the rm (or -c.rm) parameter gives the minimal and maximal acceptable distance from the central position, expressed in decimal arc minutes.

• box: the bm (or -c.bm) parameter indicates a rectangular box in the tangential projection centered on the given position, bm=x[/y] where x and y are expressed in decimal arc minutes. If y is not present, it assumes to be the same as x.
  ex: bm=10.0/6.

  Note: the x axis is always oriented along the RA or longitude on the given frame / equinox specified by the eq= parameter, and the y axis is oriented toward North; at the poles (declination or latitude value of +/-90 degrees), the orientation of the axises is undefined.

units: the specification of the size of the target is expressed in degrees with rd= or bd= parameters, and in arc seconds with rs= or bs= parameters.

Example: One specific example of this query is the query for resolving a name from SIMBAD or NED. In that case the client sends: ...?-c.obj=M31 and receives the J2000 coordinate for that object.

The mime types

Content-type: content_type (mandatory line)
Content-length: length_in_bytes (optional line)

followed by an empty line. The format in which the result is coded, the content_type, is one of the possibilities detailed in the first column of the next tables (for images, tables, and starbase). This format can be selected by the -mime= option. The possibilities are:

-mime=[html|fits|tsv|text|gif|jpeg|starbase|ps|pdf...]

(ex: tsv = tab-separated value) The relation between the -mime= argument and the content_type is:

• For images, we propose, in addition to the widely used image types (e.g. jpeg), the following astronomical mime types:

  image/x-fits	Pure FITS file
  image/x-hfits	Hcompressed FITS file
  image/x-gfits	GZIPed FITS file
  image/x-cfits	Compressed FITS file (UNIX)
  image/x-sfits	Compressed FITS file (Stark)

• For tables, we propose, in addition to the basic text/html or text/plain formats, the following astronomical mime types:

  binary/x-fits	Pure FITS file
  binary/x-gfits	GZIPed FITS file
  binary/x-cfits	Compressed FITS file (UNIX)
  text/tab-separated-values	ascii tables with columns separated by TABs (UNIX)

• For starbase:
  

  binary/x-starbase	Pure starbase file
  binary/x-gstarbase	GZIPed starbase file
  binary/x-cstarbase	Compressed starbase file (UNIX)

The default output mime type is chosen by the Server, either as one of the acceptable format defined in the client's HTTP_ACCEPT set, or ultimately server dependent.

The output list

-out=field1[,field2]...

Choice of displayed fields, ordered according to the list (table context)

-out.all

All fields are displayed on return (table context)

-out.basic

Basic (restricted set of fields) results; this exact definition is server dependent.

-out.exists

Returns just information about the number of existing answers. The answer may be the number of matching items (a positive or null number returned), or a existence flag (value -1)

-out.max=number

The maximal number of returned matching items. The default value depends on the server, but an explcit message signals a truncated result due to this limit. A value of unlimited for number could be used to remove any limitation (to be used with caution !!)

-out.next=expression

Specifies the first item the server has to return; the syntax of expression is server dependent. This parameter is of typical usage for getting the next set of matching items, once previous matching items have been returned.

-out.object

Asks to return only the matching object identification, and the corresponding sky coordinates if applicable. For astronomical objects, the returned result consists of three columns: NAME (the name of the matching object), RA (right ascension), and Dec, (declination) of the matching objects. If not otherwise specified (e.g. in FITS headers, or in the -oc option detailed below), the equinox and epoch of the positions are J2000.

The coordinate output format

-oc={hms|dms|deg}[,eq=equinox][,ep=epoch]

Specifies the format of the coordinates returned by the server. The conventions are similar to the -c= parameter for specifying the Query by position; the same hierarchical option expansion is possible, e.g. -oc.eq= specifies the equinox of the output coordinates.

The default coordinate format is server dependent.

The sort fields

List of field names on which the output is (increasingly) sorted. The default result ordering is server dependent.

Specification of the resolver

-resolv={ned|simbad}

Specifies which name resolver (conversion of object name into a position on the sky) to be used by the server. If not present, it is up to the service provider to select.

Specification of meta queries