Cartes du Ceil and the Virtual Observatory
Revised 29th May 2018
or the Virtual Observatory meets the real world !
Cartes du Ciel (CdC) is a Planetarium Program available as freeware which can be downloaded from the Internet. This is a very powerful programme that has a large feature set. In common with most similar programmes in addition to the planetarium functions it allows you to control a telescope using the ASCOM drivers. It can also follow the position of your telescope using the same connection.
Amongst the other features you would expect to find in a planetarium programme CdC can send and receive positions from Virtual Observatory applications using the SAMP (Simple Application Messaging Protocol) hub and protocol. This open up a number of possibilities which include downloading Astronomical Catalogues into an application such as TopCat and then sending the individual objects to CdC. If you have CdC connected to your telescope this can be instructed to slew to the object. Another option is to transmit positions from CdC to Aladin - this way you can get a more detailed image of the sky than is possible in CdC and also allow for various catalogues to be overlaid on the Aladin Image. This includes overlays such as Simbad that contains over 8 million stars and galaxies though not all are observable with an optical telescope.
A number of Virtual Observatory Applications use SAMP to allow information to be passed from one application to another. In this case we are constrained to position information but this still allows you to achieve lot of interoperability.
The simplest option to start with is to connect CdC to the VO programme Aladin. The operation is quite simple - it is easier to use if you have a large screen or two or more screens so you can see both windows at once. The steps are as follows:
Having connected the applications with SAMP you can now use the interoperability. A couple of examples follow. A tip to remember is that Aladin does not contain details of the planets nor the Sun.
To transfer a position from CdC to Aladin
That's it - easy !
To transfer a position the other way
That's it - even easier
Just be aware that the orientation of the two displays may not be the same and the view through your telescope may be different again.
Also CdC as no concept of the horizon or daylight so it is quite possible to select objects below the horizon or select an object near the Sun in daylight
A couple of suggestions of things that you can use this for.
One thing to be aware of - CdC can be set to check for a SAMP hub at startup (Setup - General - SAMP) however if you start the application with the SAMP hub after CdC you need to manually connect using ( View - SAMP - Connect to SAMP hub)
With TopCat you need to set the appropriate activation action (Views - Activation Actions - then tick the box for 'Send Sky Co-ordinates' as shown below)
© John Murrell 2018
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