class gammapy.background.ReflectedRegionsFinder(region, center, angle_increment='0.1 rad', min_distance='0 rad', min_distance_input='0.1 rad', max_region_number=10000, exclusion_mask=None, binsz='0.02 deg')[source]

Bases: object

Find reflected regions.

This class is responsible for placing Reflected regions for a given input region and pointing position. It converts to pixel coordinates internally. At the moment it works only for circles. If you want to make a background estimate for an IACT observation using the reflected regions method, see also ReflectedRegionsBackgroundEstimator

region : CircleSkyRegion

Region to rotate

center : SkyCoord

Rotation point

angle_increment : Angle, optional

Rotation angle applied when a region falls in an excluded region.

min_distance : Angle, optional

Minimal distance between to reflected regions

min_distance_input : Angle, optional

Minimal distance from input region

max_region_number : int, optional

Maximum number of regions to use

exclusion_mask : WcsNDMap, optional

Exclusion mask

binsz : Angle

Bin size of the reference map used for region finding. Default : 0.02 deg


>>> from astropy.coordinates import SkyCoord, Angle
>>> from regions import CircleSkyRegion
>>> from gammapy.background import ReflectedRegionsFinder
>>> pointing = SkyCoord(83.2, 22.7, unit='deg', frame='icrs')
>>> target_position = SkyCoord(80.2, 23.5, unit='deg', frame='icrs')
>>> theta = Angle(0.4, 'deg')
>>> on_region = CircleSkyRegion(target_position, theta)
>>> finder = ReflectedRegionsFinder(min_distance_input='1 rad', region=on_region, center=pointing)
>>> print(finder.reflected_regions[0])
Region: CircleSkyRegion
center: <SkyCoord (Galactic): (l, b) in deg
    ( 184.9367087, -8.37920222)>
    radius: 0.400147197682 deg

Methods Summary

find_regions(self) Find reflected regions.
make_reference_map(region, center[, binsz]) Create empty reference map.
plot(self[, fig, ax]) Standard debug plot.
run(self) Run all steps.
setup(self) Compute parameters for reflected regions algorithm.

Methods Documentation


Find reflected regions.

static make_reference_map(region, center, binsz='0.02 deg')[source]

Create empty reference map.

The size of the mask is chosen such that all reflected region are contained on the image.

region : CircleSkyRegion

Region to rotate

center : SkyCoord

Rotation point

binsz : Angle

Reference map bin size. Default : 0.02 deg

plot(self, fig=None, ax=None)[source]

Standard debug plot.

See example here: :ref:’regions_reflected’.


Run all steps.


Compute parameters for reflected regions algorithm.