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MAST Cross Correlation Help

This page explains how to use the MAST cross-correlator.

You can use this page to cross-correlate a list of sky positions with any of the mission data sets archived within MAST. To use the form, you will need a file containing the list of sky positions you want to use as an input catalog. The format of this file is discussed below. Also, select which missions you want to cross correlate this input catalog with. You can optionally specify a search radius for each mission different form the default given in the page.

The MAST cross-correlator will then parse your input catalog and begin polling the selected mission databases to see which missions have observations at your catalog potisions. The results will be presented in a simple tabular form, with links to the MAST search pages for individual missions.

Format of the Input File

The input file should have one entry per row; blank lines and lines beginning with a # character will be ignored. Each row should contain columns delimited by one of the column-delimiting characters shown in the Column Delimiter popup menu in the form. (currently, these are tab, comma, pipe, semicolon, and colon). The RA and Dec can appear in any column. (Currently, the coordinates will be assumed to be equatorial with an equinox of J2000.)

Here are some examples of input-file formats:

  • Comma-delimited file, RA in column 1, Dec in column 2:
  • Pipe-delimited file, RA in column 2, Dec in column 3:
    	HD143275 | 16:00:19 | -22:37:16
    	HD157246 | 17:25:23 | -56:22:38
    	HD28497  | 04:29:06 | -13:02:54
    	HD10144  | 01:37:42 | -57:14:10
  • Tab-delimited file, RA in column 1, Dec in column 2, with a comment line (which will be skipped):
    	# RA    	  Dec
    	16 00 19	-22 37 16
    	17 25 23	-56 22 38
    	04 29 06	-13 02 54
    	01 37 42	-57 14 10
Make sure that each column is separated by only one delimiter.

Once you have your input file, in the cross-correlation form, indicate the name of the file on your system, the character which delimits the columns (see below), and the column numbers of the RA and Dec (see below). Then hit the Submit Query button. Your browser will then send the contents of your input file to our server, which will search the Archive at the positions given in your input file. (Your file will not be saved on the server; it will be deleted as soon as the cross-correlation ends or the CGI script dies.)

Path to Your Local File
The pathname to the catalog file on your disk. Your browser will send the contents of this file to the cross-correlator to use as an input catalog. Depending on your browser and your platform, you may need to give the full path to this file (e.g., /home/kimball/xcorr.lis).

Column Delimiter
This is the character that delimits the columns in your file. The choice is currently limited to tab, comma, pipe (or vertical bar), semicolons, and colons. Let us know if you think something else would be useful here.

The cross-correlator currently cannot handle input lists of fixed-length records. When we work out a reasonable interface for this, however, we'll implement it.

RA Column Number, Dec Column Number
These are the column numbers of the RA and Dec columns within your file. The first column is assumed to be column #1.

Sometimes a catalog will start with a column-delimiting character. For example, if your catalog looks like this:

	| HD143275 | 16:00:19 | -22:37:16 |
	| HD157246 | 17:25:23 | -56:22:38 |
	| HD28497  | 04:29:06 | -13:02:54 |
	| HD10144  | 01:37:42 | -57:14:10 |
then the cross-correlator will think that column 1 is always empty, so you should start counting columns at column #2. Therefore, in this example, the RA will be in column #3 and the Dec in column #4.

Select one or more missions with which to cross-correlate your input catalog. You can use the Show catalog entries that match any/all of the selected missions selector (see below) to control whether any or all missions have to match and catalog row in order for that row's results to be displayed.

Radius (arcmin)
The radius in arcminutes on which to cross-correlate the mission with the input catalog. Each mission has its own independent radius. For each mission, a default radius has been chosen that is more or less appropriate for that mission. (Later on, we may break HST up into its individual instruments, treating each one like a separate mission. In that case, these fields will have default values appropriate for that instrument.)

Show catalog entries that match any/all of the selected missions
When you select multiple missions, you can use this selector to control how a catalog row's results will be displayed: Set it to any to show results if the catalog entry cross-correlates with at least one of the selected missions, or set it to all to show only those entries that cross-correlate with every selected mission. For example, you might set this selector to all if you are looking for catalog entries that have been observed with both HST and IUE, or to any to find entries observed with either HST or IUE.

Display n rows per mission
Use this selector to determine how many rows from each mission will be displayed. When ALL is selected, every row found for the mission will be displayed. Optionally, you may use this selector to reduce the number of rows from each mission reported, reducing the length of the results page. The total number of rows for each mission will always be reported.