Data access & format
Find out whether a position has been observed, obtain the data, and know what arrives when you do.
Is this position observed?
Enter a position to see whether a survey tile covers it and what the observation record holds — how many nights and frames, roughly how much open-shutter time, which medium bands were taken and over what date range. The search runs against the same database that drives the pipeline, so a tile reported as observed has calibrated images behind it.
Try , , . Right ascension is read as hours when written with colons or spaces, and as degrees when written as a single number.
Enter a position to see whether it has been observed and what exists for it.
A position is matched to a tile when it falls within that tile's 1.34° × 0.90° field. Frame counts and filters are exact. Exposure time is an estimate — the frame count times the survey mean of 80 seconds per frame — and is marked ≈ for that reason.
Where 7DS has observed
The same record, drawn as a map. The projection is Mollweide and equal-area: a given area of the map corresponds to the same area of sky wherever it falls, so coverage near the pole is not exaggerated as it would be on a rectangular plot. Longitude increases to the left. Switch between equatorial and galactic coordinates, and point anywhere to read what exists at that position.
Generated Aug 4, 2026. Only tiles with at least one science exposure are shown. Target-of-opportunity pointings at arbitrary coordinates are not on the tiling and do not appear.
The broad wash across the southern sky is the Reference Imaging Survey; the heavily repeated cluster near the south ecliptic pole is the Intensive Monitoring Survey, which is why the visit scale is logarithmic. Isolated tiles elsewhere are target-of-opportunity follow-ups that fell on the tiling.
Obtaining data
There is no public archive interface yet. A complete record of every image type and source catalog is held internally, with the provenance of any product traceable back to the raw frames it was built from, and requests are handled by the project directly until a public release is made.
A request is quickest to fill if it states the tile identifier — or the coordinates — the filters, the epoch range, and which product is wanted: single exposures, coadds, difference images or catalogs. Terms of use and acknowledgment are set out under how to use the data.
Include the tile identifier or position, the bands, the epoch range and the product type.
Contact the projectWhat the pipeline produces
The basic data product of the survey is a 300-second coadd of three 100-second exposures, with a source catalog attached to every processed single, coadd and difference image. Coadds are flux-scaled to a zero point of 23.9 AB magnitudes, which puts each pixel directly in units of microjansky - a convenient convention for the pixel-based, IFU-like analysis that medium-band data invite. Quality-assurance metrics including seeing, ellipticity, 5-sigma depth and astrometric precision are written to FITS headers and ingested into the database for every image produced.
- single
A calibrated individual exposure, 100 s, with WCS and a source catalog
- coadd
Three singles combined to a 300 s frame — the basic survey product
- difference
A coadd minus its reference image, for transient detection
- catalog
A flux-calibrated source list attached to every image above
- master frame
Bias, dark and flat, generated nightly and matched by group key
| Photometric system | AB magnitudes |
|---|---|
| Coadd zero point | 23.9 AB — pixel values in µJy |
| Astrometric reference | Gaia DR3 |
| Flux calibration | Synthetic photometry from Gaia XP spectra |
| Tiling | HEALPix-derived, T00000 – T28519 |
| File format | FITS, with QA metrics in the header |
Header and catalog information
Quality-assurance metrics are written into the FITS header of every product and ingested into the operations database, so the state of an image can be inspected without opening it. Each catalog is a flux-calibrated source list matched to its parent image, carrying positions on the Gaia DR3 frame and AB magnitudes in the band of the image it was extracted from. For a coadd this means one row per detected source per band; combining bands for a given source gives the medium-band spectral energy distribution that the survey exists to produce.
| SANITY | Boolean; false means the image should not be used for science |
|---|---|
| REJ_PROC | The processing stage at which SANITY was set false |
| SEEING | Measured PSF FWHM |
| UL5_5 | 5σ limiting magnitude |
| ELLIP | Point-source elongation |
| PPFLAG | Bitmask recording compromises in master-frame selection |
How a night is reduced
Images are grouped by their properties — unit, filter, observing mode, night — into configurations, and each group runs through the same sequence. Established astronomical software does the numerical work behind Python interfaces rather than being reimplemented, so the behavior of each stage is that of the underlying tool.
- 01
Preprocess
Bias, dark and flat correction against master frames matched to the science data by camera, gain, binning, unit, night and filter. Raw frames sharing a master set are loaded as a cube and processed by array broadcasting, reducing per-image time to about one second under optimal conditions, and to 3.3 ± 2.0 s in routine operation; GPU preprocessing through CuPy is available as an option, though the throughput gain in this deployment is minimal. Master-frame selection quality is recorded as a bitmask in the FITS header so that a compromise is always visible downstream.
- 02
Astrometry
World coordinate solutions against Gaia DR3, pre-cut to RIS tiles and to HEALPix cells for arbitrary pointings. SCAMP is the default engine, with Astrometry.net as a fallback for blind solves. This is also the first stage that extracts sources, so it generates the image-quality metrics: astrometric separation statistics, field vertices and position angle, PSF size and elongation in radial bins, and source counts against a magnitude-limited reference.
- 03
Photometry
Flux-calibrated source catalogs from SExtractor, in fixed apertures and in the AUTO aperture. Zero points come from synthetic photometry integrated from Gaia XP spectra over each 7DT bandpass — an unusual advantage for an instrument with an unusual filter set. The module runs on single, coadd and difference images alike.
- 04
ImCoadd
Background subtraction, zero-point scaling, weight maps, bad-pixel interpolation, PSF homogenization, reprojection and combination via SWarp with a LANCZOS3 kernel. Flux scaling is defined to put the coadd at a zero point of 23.9 AB, so that pixel values carry units of microjansky.
- 05
ImSubtract
Difference image analysis with HOTPANTS against a reference of the same field. Because of the unusual filter set, 7DT uses homogeneous references from RIS taken with the same instrument; Pan-STARRS templates are available as an option for the broad bands. Difference imaging is skipped where no reference exists yet.
| SExtractor | Source extraction and photometry |
|---|---|
| SCAMP | Astrometric and photometric solution |
| SWarp | Reprojection and coaddition |
| HOTPANTS | Difference image analysis |
| Astrometry.net | Blind astrometric fallback |
| CuPy | GPU-accelerated preprocessing |
| Gaia DR3 / XP | Astrometric and spectrophotometric reference |
Planned public release
A public release of survey products is being prepared alongside the completion of the Reference Imaging Survey, whose first full cycle is anticipated by the end of 2027. The release is intended to include a query interface over images and catalogs; this page will carry it when it exists.