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.

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)

Related Topics

Working with FITS Format

FITS Header Editor

FITS Header Pane

World Coordinate System

World Coordinate System Keywords

List COMMENT Keywords

List HISTORY Keywords

List Statistics Keywords

Add Metadata


Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All Rights Reserved.