Region Descriptions
Region Properties
Region File Format
Composite Region
Template Region
External Region Files
Source/Background
The Source/Background properties flag the region for use with other analysis applications. The default is source
Example: circle(100,100,20) # source
circle(200,200,10) # background
Fixed in Size
size arguments
[num]
# context-dependent (see below)
[num]"
# arc sec
[num]'
# arc min
[num]d
# degrees
[num]r
# radians
[num]p
# physical pixels
[num]i
# image pixels
When a "pure number" (i.e. one without a format directive such as 'd'
for 'degrees') is specified, its interpretation depends on the context
defined by the 'coordsys' keyword. In general, the rule is:
All pure numbers have implied units corresponding to the current coordinate system.
If no such system is explicitly specified, the default system is implicitly assumed to be PHYSICAL. In practice this means that for IMAGE and PHYSICAL systems, pure numbers are pixels. Otherwise, for all systems other than linear, pure numbers are degrees. For LINEAR systems, pure numbers are in the units of the linear system. This rule covers both positions and sizes. The input values to each shape can be specified in several coordinate systems including:
FK4,
B1950
# sky coordinate systems
FK5, J2000
GALACTIC
ECLIPTIC
ICRS
PHYSICAL
# pixel coords of original file using LTM/LTV
AMPLIFIER
# mosaic coords of original file using ATM/ATV
DETECTOR
# mosaic coords of original file using DTM/DTV
WCS,WCSA-WCSZ #
specify which WCS system to be used for
# linear and
sky coordinate systems
If no coordinate system is specified, PHYSICAL is assumed. PHYSICAL
or a World Coordinate System such as J2000 is preferred and
most general. The coordinate system specifier should appear
at the beginning of the region description, on a separate line (in a
file),
or followed by a new-line or semicolon; e.g.,
The use of celestial input units automatically implies WORLD
coordinates of the reference image. Thus, if the world coordinate
system of the reference image is J2000, then
is equivalent to:
Note that by using units as described above, you may mix
coordinate
systems within a region specifier; e.g.,
Composite Region
A Composite Region is a region which is a collection of other regions, which share common properties. A composite region is composed of a center point and a rotation angle, of which all its members are rendered in reference to. A composite region is defined by the # composite x y angle declaration followed by a number of regions who are or'd together. A composite region is manipulated as a single region within ds9. A composite region maybe created from the current selection of regions by selecting the Create Composite Region menu option. Likewise, a composite region can be desolved by selecting the Desolve Composite Region menu option.Template Region
A Template Region is a special form of a region which is saved in a special wcs coordinate system WCS0. WCS0 indicates that the ra and dec values are relative to the current WCS location, not absolute. A template region can be loaded at any location into any fits image which contains a valid wcs. For example, a user may create a series of regions, which represent an instrument template. Then, by selecting the Save As Template menu option, a template region saved. The user may now load this templated into any other fits image which contains a valid WCS.