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:


  • Start CdC and connect to your telescope if required in the normal way
  • Start Aladin - you will need a broadband Internet connection to download the data.
  • In CdC - File - SAMP - Connect to SAMP hub ( you can set this to happen when CdC starts automatically  using File - SAMP- SAMP Setup)
  • The little icon that looks to me a bit like a radio telescope in the bottom right of the Aladin window should be showing some 'radio waves' coming out of it to show it is connected and hovering your mouse over it should show the SAMP connected tooltip.
  • If you wish you can also check in CdC by executing File - SAMP - SAMP Status. This should show connected and also shows the applications that are connected to the SAMP hub. In this case it will only be Aladin but you can have more than one application connected.
  • That's all - if you set the connection to automatic and don't feel the need to check you don't in fact have to do anything just open the applications.


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

  • Move CdC to the required Position using the search or calendar or alternatively you might have it following your telescope.
  • Right click on the object who's position you want to transfer to Aladin.
  • From the menu pick SAMP Send Coordinates - Aladin (You can also transfer them to other applications if you have them connected to the hub either individually or to all)
  • Not a lot will appear to have happened in Aladin if you had nothing open but it should have moved to the co-ordinates
  • If you then open a an image for instance the DSS image in Aladin or the Simbad catalogue it should appear centered on the position sent from CdC. If it is not centered send the position from CdC again.

That's it - easy !


To transfer a position the other way

  • Move Aladin to the required object for instance by typing it in the search box.
  • CdC should move to the same position automatically
  • If you have your telescope connected it should slew to the same position.

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.

  • Aladin does not contain details of the planets - if you want to see the star field round a planet you can send the planet position from CdC to Aladin and it will center on the position - the planet should be where the cursor is.
  • If you want to image or view a quasar or other object that is not in the CdC catalogue. Find the object in Simbad for instance 3C273
  • On the bottom of the page open the Aladin Applet - it may be best to close the original copy of Aladin but it will work with both open.
  • When the Aladin Applet has opened you need to right click on the SAMP indicator and Broadcast Selected Planes CdC ( and your original copy of Aladin if still open) should move to the position of 3C273 as well as your telescope
  • You can download a catalogue from Vizier either full or partial and then transfer it to CdC so the objects appear just like other catalogues. I have found a couple of problems with this however. First Vizier does not seem to want to talk directly to CdC even if you have started an independent SAMP hub. Not sure why this is but if you open TopCat as well which will provide the hub Vizier will broadcast to TopCat Ok. TopCat can then be used to broadcast the table to CdC - this seems to hang at the end but the data still seems to arrive though I have not checked for any corruption or missing data which probably will happen on the last line.


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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