How do I...
Get a random 1% (or x%) subset of the SDSS data?
The SDSS catalog database is about a terabyte (1,000,000 MB) - far too big for you to download and work with it all at once. But
you can get a random subset of the data using an SQL Search
(link opens in a new window). To learn more about SQL, see SkyServer's SQL Tutorial
and guide to Using SQL with SkyServer.
- Go to the SQL Search page (link opens in new
window). From the astronomers' main page, look under Search Tools. From the public main page, look
under SkyServer Tools, then Search.
- In the large textbox, type the following SQL query:
SELECT u, g, r, i, z |
FROM Galaxy |
WHERE htmid*37 & 0x000000000000FFFF < (650 * 1) |
- The query will return a 1% subset of the data. To return a different percentage subset of the data,
change the final 1 to a different number (for example, for a random 0.5% subset of the data, change it to 0.5).
- The query will return the magnitudes of a 1% subset of the data. You can also return other data, such as
positions and object IDs.
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