Accessing the Variable Star Plotter Via the Get Method

While for normal situations accessing the Variable Star Plotter (VSP) [1] via the form is the way to go, if a program is being written that will display a chart, or someone wants to embed a specific chart on a web page, a chart can be created by creating a URL with chart parameters embedded in it. This is known on the web as the GET [2] method. This page documents how to do this for VSP.

The URL begins like so:

http://www.aavso.org/cgi-bin/vsp.pl?

Then a string of variables is added to specify the desired chart and its desired appearance. For example, if a 2° chart for Z UMa with a limiting magnitude of 11.5 and a chart title of "Great Bear Variable" was wanted, the URL would look like:

http://www.aavso.org/cgi-bin/vsp.pl?name=Z UMa&charttitle=Great Bear Variable&fov=120&maglimit=11.5

That will give a chart on a blank web page. The following URL will give the same chart, but with the web site's header and footer included:

http://www.aavso.org/vsp/chart?name=Z%20UMa&charttitle=Great%20Bear%20Variable&fov=120&maglimit=11.5

The "?" starts off the variable list, and a "&" separates the specific variables. Strings are not put in quotes.

Here are the variables that can be accessed.

name - The name of the star in question. Z UMa or U Gem are examples.
chartid - This variable can be used if you know the chart ID of a specific chart to regenerate.
ra - If a specific area of the sky is wanted, input its RA in the form HH:MM:SS.SS
dec - If a specific area of the sky is wanted, input its declination in the form +DD:MM:SS.S
ccdtable - Specifying ccdtable=on will generate a Field Photometry for your chart instead of a sky chart.
charttitle - This will be displayed at the top of the chart page. Remember strings don't have quote marks.
chartcomment - These will appear at the bottom of the chart.
dss - Specifying dss=on will load a Digital Sky Survey photograph instead of plotting stars on a white background.
forcelines - Specifying forcelines=on will force lines to be drawn from all magnitude labels to their  corresponding stars.
fov - Field of view, expressed in minutes of arc.
maglimit - This variable will specify the faintest magnitude visible on the chart.
othervars - If gcvs is specified the chart will show all GCVS variables in your chosen field. If all is specified the chart will show all known variables in the field.
printable - You can specify yes or no with this variable. If no (the default) is specified, the chart will have a screen resolution of 75dpi. If yes is specified, it will have a resolution of 150dpi and the header and footer HTML code will not be displayed.
delimited - this will publish a list of the comp star photometry in a tabular forma [3]t.
north - This can be set to up or down. The northern edge of the field will be oriented in that direction.
east - This can be set to right or left. The eastern edge of the field will be oriented in that direction.

Are any of these variables absolutely needed as a minimum? No one specific variable is needed, but at a minimum a chart must have a star name specified, or an RA and Dec, or a chartid. All the other variables listed above are modifiers.