Astronomical Catalogs Query Pages

How To

• First find the catalog you are interested in. You can browse the official list of catalogs to get a feeling for what we offer.
• Use the query form to select which fields you want to see in your output. Some tables have tens of fields, of which perhaps only a small number are of interest to you personally. You can improve performance and simplify your subsequent use of the data by retrieving only the fields you really want. Use the Print? buttons to select and deselect fields.
• Use the query form to constrain the values of certain fields; for example, if you want to see only objects of magnitude 2 and brighter, and there is a field V which is magnitude, then enter <= 2 in the selection expression ("Match Value") box for field V.
• Press the Search button at the end of the form.
• Wait; response time will depend on how many records you selected, the size of the catalog, and whether you used indexed fields in your query, as well as on network load and demand on the sybase and www servers.
• View your results, which will appear in a results page. The results page tells you how many records you retrieved and also shows you the actual SQL query that was executed. Your results appear as a simple set of data in fixed format, one column for each column that you requested.
• If you like your results, use your Web Client's Save option to save the results page as an HTML file. Your retrieved data will appear as a preformatted block of text in that file. It should be fairly easy for you to import these data into other utilities.

Also, a handful of very basic statistical functions (max, min, avg, sum) are accessible via the Func box for each field. You can, for example, discover the average radial velocity of all objects with [some set of characteristics that you determine]. Remember that when you request a stat function, you will not get multiple records of raw data, but only one record with one value for each column on which you requested a stat function.

• I select the Bright Star Catalog, and I see the Query Page for this catalog. There is a table with one line for each field in the catalog, consisting of the field name, the Print button, the Func option (if the field is numeric) and the Match Value option.
• I can't remember what the fields mean, so I click on the data dictionary information for this catalog, and remind myself what it is I want to look at.
• I decide I want to see the HR number, name, DM number, SAO number, RA hours and minutes, Dec degrees and arcminutes, and magnitude of all the stars that are magnitude 1.5 or brighter.
• I make sure the Print buttons for fields HR, SAO, Name, DM_cat, DM, RAH, RAM, DecSign, DecD, DecM, and V are selected. Now that I have selected the fields of interest, I need to select only the records of interest.
• I enter the expression <= 1.5 in the Match Value box for field V. Now my selection is complete.
• I press the Search button at the end of the form. I wait about 10-15 seconds.
• I get a page labelled "SQL and Results" which shows me a SQL statement (the one which was generated for me) and 37 rows of result data. I'm using Netscape, so I choose Save As... from the File menu and save the output page to a text file.
• I now have a list of extremely bright stars. I wonder what their average radial velocity is?
• I return to the query page and select the Print button for field RadVel. I then enter avg into the Func box for field RadVel.
• I hit the Search button again. After a few seconds I get another Results page, which tells me that the average of RadVel for this set of 37 records is 1.

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