This outline of how to delve into the Sloan Digital Sky Survey (SDSS) database is based on my experiences of October - November 2000 at Princeton. It is an evolving and no doubt incomplete document. See the glossary at the end for definitions of capitalized Words. See also Brian Lee's Fermilab SDSS page. Pat Hall -- pathall[at]astro.princeton.edu
OVERVIEW (1) Get a Fermilab computer account. This will be needed to get the latest data from Fermilab, although at Princeton copies of such data are generally maintained by the data gurus. See Brian Lee's guide to getting a Fermilab account for instructions and a guide to SDSS use of Fermilab computers. First, ask jen_a[at]fnal.gov Jennifer Adelman (or another authorized contact at Fermilab) to request a Fermilab ID Number for you. Then you can request an account here, but if you do not have any preexisting Fermilab account, you must also read, sign, and return the Fermilab Policy on Computing. You will be issued two accounts at Fermilab: one for the mail server and one for the UNIX cluster, which is the one you'll be using. (2) Get an SX account (SX is the Science eXtractor interactive database at JHU). Mail jen_a[at]fnal.gov Jennifer Adelman at Fermilab to get one. Once your account is issued, you will ssh to sdssdp4.fnal.gov to set it up, as per the instructions you'll be given; you will not need an account of your own on sdssdp4 to do this. Robert Lupton may allow you to use his sx account until yours is set up; see the SX entry under CATALOG DATA below. (3) Get the SDSS account name and password for access to SDSS-only websites from non-SDSS computers (e.g. from home, or when you're observing). Ask Jill Knapp or Zeljko Ivezic for this information. (4) Subscribe yourself to the sdss-general mailing list at least, plus any other mailing lists of interest, at this website. (5) The Princeton SDSS web page is http://www.astro.princeton.edu:81/ From here you can read the SDSS Project Book for a basic introduction, and link to the main SDSS site (where you might want to read about SDSS Rights and Responsibilities), SDSS sites at other institutions, and many other websites of interest. (6) The Princeton SDSS data web page is http://www.astro.princeton.edu:81/documents/PeytonSDSS.html This provides links to several of the documents discussed below. NOTE that the "Jump Starting Photo" section of Vogeley's Photo Primer is out of data; to start photo, do one of the following. --on tanuki or moonshine at Peyton Hall: source /u/products/etc/sdssfue.csh setup photo -r ~ivezic/photo photo global data_root set data_root /u/dss/data set_display 1 --on fsgi03 (and possibly sdssdp2/3) at FNAL, Edit your .cshrc to include the following two lines: setenv UPS_EXTRA_DIR /afs/fnal.gov/files/code/sdss/p/upsdb source /afs/fnal.gov/files/code/sdss/p/sdss.cshrc plus the following, if it's not already in there: source "/afs/fnal.gov/ups/etc/setups.csh" then type: setup photo #latest version: setup photo -r ~ivezic/photo photo global data_root set data_root /usr/sdss/data01/imaging set_display 1 (You can also do "setup sm", "setup idl", "setup spectro".) --for Linux machines at Peyton Hall (unverified): setup photo -r ~ivezic/photoLinux "although there are some occasional NaNs not yet understood." Note that currently fsgi03 has the most complete collection of runs. (7) Zeljko Ivezic's SDSS page has useful introductions to Photo and the GNATS bug reporting system. Use "sdss" as username and password for GNATS. (8) If you start playing around with data in Peyton, you'll rapidly run up against your disk space quota. Use the scratch disks instead: /peyton/scr/[machinename][scratchdisk#] e.g. /peyton/scr/hecate4 These disks can be accessed from any machine, not just hecate (e.g.). (FYI this is found on page 5 of "Guide for Living (in Peyton Hall) I: Computing") Other Peyton Hall computing info can be found here.
CATALOG DATA (1) The SX database at JHU will be the "end product" of, and interface to, SDSS. Click on Documentation, where you can select the online SX Query Tool and Language Manual (including sample queries), a discussion of SX classes, and a discussion of SX flags. See the SX database webpage at Fermilab for the contents of the SX databases at Fermilab. See the Princeton SDSS data web page for how to run SX at Princeton. Use /u/rhl/sxQueries/loaded.sxql to find out what data is currently loaded into SX. (2) See the Princeton SDSS data web page for how to read Photo outputs using SM (currently this is found in Rita Kim's introduction to SDSS data at Peyton). (3) Read Michael Vogeley's Photo Primer via the Princeton SDSS data web page for how to look at the catalog data using photo. At Princeton, SDSS data (TsObj files) can be found in /u/dss/data/ and the main SDSS computer to use is coma, not fsgi03.fnal.gov as listed in this primer. (4) See also Brian Lee's Fermilab SDSS page.
SPECTRA (1) See Dave Schlegel's guide to looking at spectra: http://spectro.princeton.edu/ At Princeton idl2dspec-format data is in /u/dss/data/2d_v4_7/ and spectro1d-format data is in /peyton/scr/ginka0/vijay/sdss_spectra/ Until the SM link on the above page is up, you should read /u/strauss/spectro_sm/README to see how to use SM to look at spectra. (2) You can also access plots of some spectra, if you know the plate, MJD, and fiber number you want, at http://sdsslnx.fnal.gov:8015/specindex.html From each spectrum plot page you can access the image of that object as described in point (1) under IMAGES below; the field in which it is found will be plotted, with the object circled in yellow. The link to the object's Photo parameters does not yet work. (3) Eventually SX will include spectra (V2.1, 2000?) (4) See also Dan Vanden Berk's how to display SDSS spectra page. (5) See also Brian Lee's Fermilab SDSS page. (6) At Fermilab, spectra are stored in /usr/sdss/data05/spectro/1d_10/plate/1d/ where 1d_10 is the version number, subject to change, and plate is the plate number of interest.
IMAGES (1) You can access images by Run, Stripe, and Field at http://sdsslnx.fnal.gov:8015/ In any field plot, you can click on any position to get its RA and DEC. You can then search NED, MAST (Multimission Archive at Space Telescope), FIRST or SIMBAD at that position. There is also a "fetch Photo params" link, presumably for the object nearest the position of the cursor, but it does not yet work. (2) There is an atlas image server. For details, see sdss-obpd message 144. (3) See also Brian Lee's Fermilab SDSS page. (4) See Zeljko Ivezic's Photo toolbox page for how to produce postage stamps or finding charts from within Photo. (5) At Fermilab imaging data is stored in /usr/sdss/data01/imaging/
MISC (1) To set up your own website in the password-protected SDSS website area, ask the computer gurus to create you a directory under "/u/dss/". You can then access the files in /u/dss/pathall/ (for example) as http://www.astro.princeton.edu:81/pathall/ Please don't use your /u/dss/ directory to store data, but e.g. drafts of SDSS papers which shouldn't go on a public site are OK.
GLOSSARY Field Each camera column (scanline) in a Strip is broken down into a number of roughly square, slightly overlapping Fields on which Photo is then run. Photo The atlas image creation, object detection, and photometry pipeline. Plate A plug-plate of 640 fibers. Each spectrum is uniquely identified by its Plate number, the MJD (Modified Julian Date) of the observation, and the Fiber number. Run Each time the imaging camera is powered up is a different Run. Strip 6 scanlines of imaging data separated by about one scanline width each (a scanline is the track of one camera column across the sky). Stripe Two Strips are merged into a filled Stripe about 2.5 degrees wide. SX Science eXtractor interactive SDSS database at JHU. TsObj FITS table containing all Photo info on all objects in a given Field.