Gator Documentation:
Single Object Search
Overview
The Coordinate/Object field combines in a single interface the name resolution look-up services of NED and SIMBAD as well as coordinate transformation services.
The same input field is used for either name resolution or coordinate input and the service dynamically determines its content. Gator accepts both decimal degree and sexigesimal inputs. If the input field contains a string which can be interpreted as a coordinate representation, it is used as such. If not, the string is sent first to NED, then to SIMBAD to attempt name resolution. The range of name formats acceptable is set by those projects.
Coordinates entered into the interface allow for all information to be contained in a single string. The parser is very forgiving, so all of the following are valid (and give the results you would expect). For coordinate inputs, Equatorial J2000 is assumed unless specified otherwise.
- 0042443-411608
- 00:42:44.3 -41:16:08
- 00h42m44.3s -41d16m08s
- 00 42 44.3 -41 16 08
- 34.5565 54.2321 gal
- 34. 54. ecl
- M83
- 344.489624 40.248115 Equ B1950
- Barnard's Star
Putting all the information in one field has the advantages that cutting and pasting from other sources can be done quickly and data entry in general can be performed without moving back and forth between the keyboard and mouse.
This same entry field appears in many other IRSA services where names or coordinates are required.
Cone Search
When performing a Single Object search, you may specify circular or elliptical geometries using the Cone Search.
-
Circular "cone" Search: You need only to specify
the radius of the search and leave the 'PA' and 'Axial
Ratio' fields blank.
Example:
coordinate: 10.68468 41.26904 Equatorial J2000
radius: 60 arcsec -
Elliptical Search: you must specify the
semi-major axis, axial ratio (b/a), and position angle
(East of North, standard orientation).
Example:
semi-major axis: 630 arcsec
position angle: 52 deg
axial ratio: 0.26
Note: When using table upload, leaving the value of radius or semi-major axis as blank or zero results in using radius, PA, and axial ratio values as defined in the user-supplied table.
Box Search
The search region is an area centered at the source position, with sides equal to the length specified in the "Size" field.
Polygon Search
The polygon search option allows the selection of all catalog sources lying within an irregular polygonal area defined by a set of vertices. Users specify the convex polygon area (none of its interior angles larger than 180 degrees) by entering a series of vertices in the dialog box on the query page.
- Each vertex is defined by a J2000 RA and Dec position pair, in decimal degrees;
- A maximum of 15 vertices is allowed;
- Vertices must be separated by a comma (,);
- Do not put a comma at the end of string of vertices
- You do not need to repeat the first vertex - Gator will close the polygon.
Example: Define a search area which is a box in the sky with length of 1 degree in Equatorial J2000. In the provided input text area, on the query page beside Polygon Search, input:
20.5 21.5, 20.5 20.5, 21.5 20.5, 21.5 21.5
Then Gator will perform a polygon search with this spatial constraint.
