Visit image#
Individual processed and calibrated sky images.
Citation: NSF-DOE Vera C. Rubin Observatory (2025); Legacy Survey of Space and Time Data Preview 2: visit_image dataset type 
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Access#
The visit images are accessible via the Butler, SIA, and TAP services.
Butler#
Dataset type: (‘visit_image’, {band, instrument, day_obs, detector, physical_filter, visit}, VisitImage)
Format: FITS
Number of Butler datasets:
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SIA and TAP#
Schema: ObsCore table
IVOA calibration level: 2
Dataproduct subtype: lsst.visit_image
Description#
Raw images from the camera undergo processing that includes instrument signature removal (ISR), image calibration (photometric and astrometric), and PSF estimation. The result is a fully calibrated visit image.
Each individual visit image contains data from one of the camera’s detectors.
Visit images are rotated, and are not aligned north-up east-left, such that RA, Dec do not correspond to x, y.
Processing#
The visit images are the result of Image calibration.
Pixel data#
The visit 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 Visit and difference image mask planes.
Metadata#
The metadata for visit images retrieved from the Butler include the derived PSF and the WCS.
Pixel scale#
The pixel scale in a visit image varies with position.
To use the pixel scale it is recommended to extract it using the “getPixelScale” method associated with the visit images’ WCS.
This function should always be given an argument with x, y coordinates, so that a typical call (for an x, y position of 1000, 1400) may look like: wcs.getPixelScale(lsst.geom.Point2D(1000, 1400)).asArcseconds() (where “wcs” is the WCS associated with a visit image, the “Point2D” function comes from the “lsst.geom” package, and the final portion converts the result to arcseconds).
Tutorials#
See the 200-level catalog Tutorials for a notebook on visit images.