Template coadd#
The combination of processed images with the best seeing, for a patch of sky and for each of the six LSST filters, to be used as a template for difference imaging.
Citation: NSF-DOE Vera C. Rubin Observatory (2025); Legacy Survey of Space and Time Data Preview 2: template_coadd dataset type 
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Access#
The template coadd images are accessible via the Butler, SIA, and TAP services.
Butler#
Dataset type: (‘template_coadd’, {band, skymap, tract, patch}, ExposureF)
Format: FITS
Number of Butler datasets:
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SIA and TAP#
Schema: ObsCore table
IVOA calibration level: 3
Dataproduct subtype: lsst.template_coadd
Description#
The LSST all-sky map is divided into “tracts”. One tract is one square region of LSST’s all-sky tesselation (“skymap”), $~1.66$ deg per side. Tracts are subdivided into 100 overlapping patches, and one template coadd image is created per patch.
Processing#
The template coadd images are the result of Image coaddition, and they are used in Difference image analysis (DIA).
Pixel data#
The template coadd images have three planes of pixel data.
Image: sky pixel data in flux units of nJy.
Variance: uncertainty (noise) in the flux in units of nJy^2.
Mask: an integer bitmask of representative flag values that indicate processing status or issues. See Deep and template coadd mask planes.
Metadata#
The metadata for template coadd images retrieved from the Butler include, e.g., the PSF, the WCS, and a list of input images.
Tutorials#
See the 200-level catalog Tutorials for a notebook on template coadd images.