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 Post subject: Aladin Sky Atlas
PostPosted: Mon Jan 28, 2019 8:46 pm 
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Joined: Fri Dec 10, 2004 10:34 pm
Posts: 356
Location: Surrey
There are a number of free and paid for Sky Atlases available both in software and even in paper. In general the paper atlases are aimed at showing the location of objects in the sky. The software versions cover a wide range but commonly simulate what you might see in the night sky at a specified time & location, typically these will include the position of the planets and also the Sun and may include Comets and Asteroids.
One Sky Atlas that takes a different approach is Aladin from CDS in France. This atlas shows areas of the sky from the whole sky to very small areas as might be expected but its strength is the ability to show vast amounts of information on the objects in the current view. This includes multiple images (including raw & processed Hubble Images), catalogue information and also spectra. At present there are over twenty two thousands of these though some only cover very small areas of the sky.
The big strength of Aladin is the way that all the resources are hyperlinked. Selecting a group of objects in an image will show these with the most important data in a separate table and these have Hyperlinks that take you to more detailed information in the particular catalogue selected.
Previous versions had a very steep learning curve but the latest version V10 has significant improvements in usability particularly for new users but still has very powerful tools available in the background.
The best way to start is download Aladin Desktop to your computer following the instructions on the page at https://aladin.u-strasbg.fr/.

If you run the programme you will be presented with the basic interface with nothing loaded (The image of M31 is only as a frontpiece not a usable image).

Loading your first image is as simple as typing the name of the object or the coordinates in the command box. A coloured DSS image of the object or location you entered should then be displayed. You might need to zoom out or in using the zoom slider depending on the size of the object you entered.

At this stage the display will only show the image with a cross indicating the centre of the object. The next step to getting useful information is to overlay some catalogue data. The quick way to do this is to use one of the 'bookmarks' shown with orange stars above the image. I would suggest that you start with the Simbad button as some of the others may contain objects not shown on the visible image or catalogues such as the Gaia Catalogue that will probably overwhelm you with the number of objects.

Having clicked the Simbad button symbols should appear over most of the objects in the image. To find more information on an object(s) ensure the Select button is clicked to the right of the display and then use your mouse to click and drag a (rectangular) selection around the objects you are interested in.

The selected objects symbols will change colour and a table shoudl appear below the main image with summary details.

The table and the symbols in the display are linked so moving your mouse pointer over one of the selected objects will highlight the relevant row in the table and moving the mouse pointer over a row in the table will cause the appropriate symbol to flash.

Finally if you click on the blue hyperlink in the 'main_id' column will open a page of detailed information in your browser ( from Simbad).

There is much more that is possible but this is a very brief introduction.

Try this software and let us know how you get on.

John Murrell

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Engineer @ Work - Astronomer @ Play


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