List WCS Keywords

The List WCS Keywords command finds all the World Coordinate System ("WCS") related keywords in an image header and lists them into a Text window. If the Image window contains an image set, the current image or the image set may be listed according to the status of the Process Image Set flag, or button. If no WCS or WCS keywords are found, this result is listed in the window (see below).

Note that specific combinations of WCS keywords are required for the image to have a valid WCS calibration, and even one missing keyword may prevent the image from having a WCS calibration. This command may also be used to determine if the image has a WCS calibration.

This command is available in two menus: the Image Window > Edit FITS Keyword Types menu and the Image Window > Coordinates menu.

The example below lists WCS keywords from a fully calibrated image header. Note that the ".txt" extension is automatically appended to the window title after the contents were saved to a file.

WCS Projection Types

The mathematical relationship between pixel location and World Coordinates is known as the world coordinate projection. The projection type is represented in the FITS header using the CTYPEn keyword, where n refers to the axis dimension. Equatorial calibration usually employs the "Tangent Plane (gnomonic)" projection with CTYPEn Code = TAN. In the FITS header, this equatorial projection for right ascension (axis 1) and declination (axis 2) appears as CTYPE1 = 'RA---TAN' and CTYPE2 = 'DEC--TAN'.

Mira supports the types of WCS projection listed in the table below. The projection type may be obtained using the class method CImage:GetWcsType() in the Mira Pro x64 Script language. In the table below, nWcsProj is returned by CImage:GetWcsType().The CTYPEn Code is listed in FITS header as the string value of the CTYPEn keyword. The Description is reported in the output from the List WCS Keywords command.

nWcsProj	CTYPEn Code	Description
-1		Pixel WCS (default, no WCS)
0	LIN	Linear projection
1	AZP	Zenithal / Azimuthal Perspective
2	TAN	Tangent Plane (gnomonic)
3	SIN	Orthographic / synthesis
4	STG	Stereographic
5	ARC	Zenithal / azimuthal equidistant
6	ZPN	Zenithal / azimuthal Polymomial
7	ZEA	Zenithal / azimuthal Equal Area
8	AIR	Airy
9	CYP	Cylindrical Perspective
10	CAR	Cartesian
11	MER	Mercator
12	CEA	Cylindrical Equal Area
13	COP	Conic Perspective(COP)
14	COD	Conic equidistant
15	COE	Conic Equal Area
16	COO	Conic Orthomorphic
17	BON	Bonne
18	PCO	Polyconic
19	GLS	Sanson - Flamsteed(Global Sinusoidal)
20	PAR	Parabolic
21	AIT	Hammer - Aitoff
22	MOL	Mollweide
23	CSC	COBE quadrilateralized Spherical Cube
24	QSC	Quadrilateralized Spherical Cube
25	TSC	Tangential Spherical Cube
26	NCP	Special case of Orthographic / synthesis
27	DSS	Digitized Sky Survey plate solution
28	PLT	Plate fit polynomials(SAO)
29	TNX	Tangent Plane (gnomonic, NOAO with corrections)

WCS Projection Types

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