Linking from Cartes du Ceil to the Virtual Observatory (and back again)
NEW 12th July 2015
Downloading to CdC from the VO and using VO applications to view and select the data
In my other page on using Cartes du Ciel (CdC) with the Virtual Observatory(VO) I described how you can download a position from a catalogue loaded from the VO to CdC via an application such as TopCat. This allows you to point your telescope at the position of the object in TopCat via CdC but does not draw the objects on the CdC sky chart.
Following a discussion with Michael Poxon on the CdC discussion group (email@example.com) I discovered an alternative way that that enables the catalogue objects to be drawn on the CdC sky chart but also allows the VO to be used to select the particular object and to plot a whole sky chart of the particular catalogue.
In essence this method is the reverse of that on my other page, the high level steps are as follows:
There are a couple of supplementary options:
Loading the Catalogues into CdC from the VO
This function is covered in the CdC documentation here you need to scroll down to the 'VO Catalog' section. The following is based round loading a catalogue of OB associations but there are currently 13,807 to chose from in Vizier the VO web service CdC uses for catalogues.
1. Open CdC
I had a bit of a problem here as I could not get CdC to search for an object even though it appears in the catalogue. As a result I am using the following work around.
Exporting the Catalogue to TopCat from CdC
CdC allows the broadcast of VO catalogues to other applications using SAMP. The following sequence of actions achieve this:
A. Open TopCat
This shows the TopCat main screen with the Catalogue of OB associations loaded as well as another VO catalogue of Supernovae. TopCat can have lots of catalogues open.
A couple of other possible actions
TopCat has an option to plot the table data ( received from CdC) in step F above using the Sky Plotting facility. All you need to do is to select the button and select which fields in the catalogue represent RA & Dec. The table data points will then be shown on the surface of a sphere ( you are looking at the data from outside even if that is outside the Universe !). The sphere can be rotated by click and drag. If you click on one of the data points this will be selected in the TopCat table, broadcast to CdC and the CdC chart should move to the position.
A second option is to broadcast the row to Aladin as well. To do this start Aladin and in option 'I' above select 'All Clients' . NB you need to download Aladin rather than use the browser version.
This image shows the TopCat sky plot with the OB associations plotted. Note this is in galactic co-ordinates and shows how the OB associations are in the plane of our home galaxy The Milky Way. The object selected in the plot is in row 72 of the table and is shown in the image below.
Finally this screenshot from CdC shows that it has moved to row 72 the OB association SCO 2D.
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