scientific-skills/database-lookup/references/sdss.md
https://skyserver.sdss.org/dr18/SkyServerWS
Replace dr18 with the desired data release (e.g., dr17, dr16).
No API key required. All endpoints are public.
GET /SearchTools/SqlSearch
| Parameter | Type | Description |
|---|---|---|
cmd | string | Required. SQL query against SDSS CasJobs schema. |
format | string | json, xml, csv, html, votable. Default: html. |
Example — query 10 galaxies:
https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/SqlSearch?cmd=SELECT TOP 10 objid,ra,dec,u,g,r,i,z FROM PhotoObj WHERE type=3&format=json
Type codes: 3 = galaxy, 6 = star.
Response (JSON):
[
{"Rows": [
{"objid": 1237645941825863680, "ra": 195.123, "dec": 2.456, "u": 22.1, "g": 20.8, "r": 19.5, "i": 19.1, "z": 18.9}
]}
]
GET /SearchTools/RadialSearch
| Parameter | Type | Description |
|---|---|---|
ra | float | Required. Right ascension (degrees). |
dec | float | Required. Declination (degrees). |
radius | float | Search radius in arcminutes. Default: 1. |
format | string | json, xml, csv. |
limit | int | Max results. |
objtype | string | Filter: star, galaxy, or blank for all. |
Example — objects within 2 arcmin of RA=180, Dec=+0.5:
https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/RadialSearch?ra=180&dec=0.5&radius=2&format=json&limit=10
GET /SearchTools/RectangularSearch
| Parameter | Type | Description |
|---|---|---|
min_ra | float | Minimum RA (degrees). |
max_ra | float | Maximum RA (degrees). |
min_dec | float | Minimum Dec (degrees). |
max_dec | float | Maximum Dec (degrees). |
format | string | json, xml, csv. |
limit | int | Max results. |
GET /SearchTools/SqlSearch?cmd=SELECT * FROM PhotoObj WHERE objid={objid}&format=json
GET /SearchTools/SqlSearch?cmd=SELECT * FROM SpecObj WHERE plate={plate} AND mjd={mjd} AND fiberid={fiberid}&format=json
GET /ImgCutout/getjpeg
| Parameter | Type | Description |
|---|---|---|
ra | float | Required. RA (degrees). |
dec | float | Required. Dec (degrees). |
scale | float | Arcsec/pixel. Default: 0.396127. |
width | int | Image width in pixels. Default: 512. |
height | int | Image height in pixels. Default: 512. |
Example:
https://skyserver.sdss.org/dr18/SkyServerWS/ImgCutout/getjpeg?ra=180.0&dec=0.5&scale=0.4&width=256&height=256
Returns JPEG image data.
Spectrum FITS files can be retrieved from the Science Archive Server:
https://data.sdss.org/sas/dr18/spectro/sdss/redux/{run2d}/spectra/{plate}/spec-{plate}-{mjd}-{fiberid}.fits
| Table | Description |
|---|---|
PhotoObj | Photometric measurements (positions, magnitudes). |
SpecObj | Spectroscopic measurements (redshifts, classifications). |
Galaxy | View of PhotoObj filtered to galaxies. |
Star | View of PhotoObj filtered to stars. |
No formal documented rate limits. Queries returning very large result sets may time out. Use TOP N in SQL queries to limit results. For bulk data, use CasJobs (https://skyserver.sdss.org/CasJobs/) with a free account.