FAQ

Short answers to the questions people ask most, with links to the full explanation.

API 3.1 · stars release 55c97bc0c218a6c5 · SS release ef7caf53a399bc1f

Stars#

Why does a non-detection have a magnitude?: For a non-detection, mag holds the 5σ limiting magnitude and mag_err is 99.999. Select rows with detected == 1, never by testing the magnitude. See magnitudes and upper limits.
My V2 star id does not work.: V2 and V3 ids are unrelated numbers and there is no cross-match yet. Search V3 by name, coordinates or AV3 name.
Why does my star have several curves?: ASAS-SN fields overlap, so a star can be measured in two or three fields, each with its own calibration, in g and in V. Each (field, band, aperture) is a separate curve; the field and band columns tell them apart. See curves and apertures.
The website says some points are hidden. Why?: The website hides points with quality bits 0x17 (bad or saturated pixels, image not marked good, negative pixel) and tells you how many. Open the Flags menu and choose All to see them. The API hides nothing unless you ask. See quality flags.
Why did the flags of an old epoch change?: Bits 8–12 mark the worst 10% of a star's own epochs, so they shift when a release adds epochs. Bits 0–7 do not change. Cite the release you used.
My bright star scatters more than its error bars.: Star errors are statistical only. Add a floor of about 0.014 mag in quadrature for epoch-to-epoch work. See uncertainties.
Can I look up a star by its Gaia id?: Yes. Every V3 star was matched to Gaia DR3 and DR2: use /v3/stars/gaia/dr3/{source_id} (or dr2), POST up to 3 anonymous or 100 authenticated ids at once, or type the id into the search box. A Gaia source fainter than the catalog limit has no V3 star; search around its position instead. See Gaia identifiers.
Why can't the API find a star by its common name?: The server resolves only its own identifiers. The website sends names to Sesame from your browser; in a script, resolve the name first (for example with astropy's SkyCoord.from_name) and run a cone search.

Asteroids and comets#

Should I use reduced or difference-image photometry?: Leave product=auto: it uses reduced images for objects brighter than about 13.5 mag and difference images for fainter ones. Reduced-image measurements of faint objects are often blends with stars. See products.
Is jd corrected for light travel time?: No. jd is the observed UTC time of mid-exposure. Add djd_emission to get the emission time in TDB. See time columns.
My comet is fainter than the MPC magnitudes.: Sky Patrol measures the coma inside a fixed aperture (2 pixels, 16″, by default), not the total magnitude. Larger apertures give brighter magnitudes. See comets.
Every row has moving_quality 2 and 1024 set. Is the data bad?: No. These bits are set on every SS-1 row because the release has no orbit-uncertainty information. See moving_quality.
Why does encke return 300?: The name matches more than one object. The response lists the candidates; use the slug, such as 2P.

Access#

How many requests can I make?: 30 science requests per minute anonymously, 60 for registered users and 120 for users approved by the ASAS-SN team, plus daily source/byte and shared-IP limits. If you get 429 or 503, wait Retry-After seconds and retry. See rate limits.
Can I download light curves for a million stars?: Bounded batches are available: up to 3 sources anonymously or 100 with an API token, subject to daily quotas. Large asynchronous jobs are unavailable. Use the Python batch client.
The star section says it is loading.: During the beta a dataset can be offline while its data are loaded and verified. Its endpoints return 503 dataset_unavailable until it is ready; the other dataset keeps working.
How do I make sure I get the same numbers next year?: Record the release_id and serve_id of your data, and fetch through /v3/r/{serve_id}/ URLs, which always return the same bytes. See versioned URLs.
What should I cite?: See Citing Sky Patrol.