Combine bands into output channels¶

Cutana handles sources with several FITS files, one per band, and mixes them into output channels with configurable weights.

1. List the bands in the catalogue¶

Give each source every band file in fits_file_paths:

SourceID,RA,Dec,diameter_pixel,fits_file_paths
TILE_123_456,45.1,12.4,128,"['/path/to/vis.fits', '/path/to/nir_h.fits', '/path/to/nir_j.fits']"

Cutana identifies each file's band from its name, so vis.fits is VIS, nir_h.fits is NIR-H, and nir_j.fits is NIR-J.

2. Select the bands to load¶

selected_extensions decides which files of each set are loaded:

config.selected_extensions = [
    {"name": "VIS", "ext": "PrimaryHDU"},
    {"name": "NIR-H", "ext": "PrimaryHDU"},
    {"name": "NIR-J", "ext": "PrimaryHDU"},
]

3. Map bands to output channels¶

channel_weights has one key per selected band. Each value lists that band's weight in each output channel, so three-element lists produce three channels, for example RGB:

config.channel_weights = {
    "VIS": [1.0, 0.0, 0.5],
    "NIR-H": [0.0, 1.0, 0.3],
    "NIR-J": [0.0, 0.0, 0.8],
}

The keys are matched by band name, so dictionary order does not matter. Weights are not normalised.

To pick a band subset from a larger set, select only those bands and give channel_weights one entry per selected band. For the matching rules, what happens when a selection matches nothing, and how the UI discovers bands, see band selection and channel mapping.