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PostPosted: Mon Feb 11, 2019 9:45 pm 
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Joined: Fri Dec 10, 2004 10:34 pm
Posts: 356
Location: Surrey
The database that operates the CDS Astronomical Server and is the powerhouse behind aplications such as Aladin that I have mentioned in other posts have acheived a new record in the amount of data they store.

In terms of image data they have 5.21E14 bytes of image data - 521 TeraBytes - in the form on Healpix images.

In addition they have 18 billion rows of catalogue data !

This includes the Gaia DR2 but they have not yet integrated the PanSTARRS DR2 data and images.

The database delivers around 750k HealPix images a day.

If you are interested in what a HealPix image is have a look at https://healpix.jpl.nasa.gov/ which seems to give a better explanation than the Wikipedia page. The encoding allows an appropriate level of data to be shown for the level of magnification depending on the zoom setting in your application. Thus if you look at an all sky view of the Gaia DR2 data you will only be shown the brightest objects. As you zoom in you will see a smaller area of the sky but you will also see dimmer objects so the number of objects displayed essentially remains constant at least till you reach the magnitude limit of the particular survey you have selected.

John Murrell

John Murrell

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