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By using several flags together, you can limit your searches to return only objects that have clean
photometry, thereby ensuring that you have a good sample. The flags you use differ depending on whether you
are looking at stars or extended objects.
The queries below run slowly. These are test versions that use TOP 10 to return only the first 10
matching objects. To return all matching objects, remove the top 10 and use the CasJobs
batch query system (link opens in a new window), which lets you run queries that take up to 8 hours.
Also, note that lines that start with "--" are comments that are not executed as SQL statements.
For stars, use the following query to return IDs, positions, colors, and flags:
| SELECT TOP 10 objid, ra, dec, u, g, r, i, z, |
| dbo.fPhotoFlagsN(flags) as flags |
|
| FROM star |
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| WHERE ((flags & 0x10000000) != 0) -- detected in BINNED1 |
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| AND ((flags & 0x8100000c00a4) = 0) -- not EDGE, NOPROFILE, PEAKCENTER, |
| -- NOTCHECKED, PSF_FLUX_INTERP, SATURATED, or BAD_COUNTS_ERROR |
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| AND (((flags & 0x400000000000) = 0) or (psfmagerr_g <= 0.2)) |
| -- not DEBLEND_NOPEAK or small PSF error |
| -- (substitute psfmagerr in other band as appropriate) |
|
| AND (((flags & 0x100000000000) = 0) or (flags & 0x1000) = 0) |
For extended objects, use the following query to return IDs, positions, colors, and flags:
| SELECT TOP 10 objid, ra, dec, u, g, r, i, z, |
| dbo.fPhotoFlagsN(flags) as flags |
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| FROM galaxy |
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| WHERE ((flags & 0x10000000) != 0) -- detected in BINNED1 |
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| AND ((flags & 0x8100000c00a0) = 0) -- not NOPROFILE, PEAKCENTER, |
| -- NOTCHECKED, PSF_FLUX_INTERP, SATURATED, or BAD_COUNTS_ERROR |
| -- if you want to accept objects with interpolation problems for PSF mags, |
| -- change this to: AND ((flags & 0x800a0) = 0) |
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| AND (((flags & 0x400000000000) = 0) or (psfmagerr_g <= 0.2)) |
| -- not DEBLEND_NOPEAK or small PSF error |
| -- (substitute psfmagerr in other band as appropriate) |
|
| AND (((flags & 0x100000000000) = 0) or (flags & 0x1000) = 0) |
| -- not INTERP_CENTER or not COSMIC_RAY – omit this AND clause if you |
| -- want to accept objects with interpolation problems for PSF mags. |
The form below will let you practice searching for flags with SQL, using the example queries
on this page. Press Query 1 or Query 2 to load the queries, and Submit to
run the queries.
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