Sydney Observatory images attacked by an astrobot – no need to panic


A colour image of the famous Ring Nebula in Lyra created by adding images taken in three different colours. This northern hemisphere object was imaged from Sydney Observatory in October 2002 remotely using a telescope at Etscorn Observatory in New Mexico. Image Sydney Observatory

Today 20 February 2009 (Sydney time) the above image and five others were posted on the image sharing website Flickr here. Within a few minutes astrometry.net found the image and analysed it to provide full details such as the astronomical coordinates of the image centre, its scale, its orientation and marked the main objects visible on the image:

astrometry.net says:
Hello, this is the blind astrometry solver. Your results are:
(RA, Dec) center:(283.400649252, 33.042000387) degrees
(RA, Dec) center (H:M:S, D:M:S):(18:53:36.156, +33:02:31.201)
Orientation:-179.56 deg E of N

Pixel scale:1.43 arcsec/pixel

Parity:Reverse (“Left-handed”)
Field size :12.22 x 8.11 arcminutes
Your field contains:
IC 1296
NGC 6720 / M 57 / Ring nebula in Lyra

This amazing software technology has the wonderfully expressive name Fast Geometric Hashing for Automated Astrometry. Basically, it seems that the program searches through its large database of star positions and builds up another database of star patterns. It then compares these patterns with those on the image to be analysed. The system works brilliantly as can be seen for the image of the Ring Nebula. Note that it accomplishes something that is very difficult to do, since initially nothing is known of the image – in what direction it was taken, in what orientation and whether the image is from a large telescope or an ordinary digital camera pointed at the night sky from a dark location.

The Ring Nebula in Lyra may look like a ring but it seems that we are looking down a tunnel of gas ejected by the central star. The colours indicate the different gases that are excited, as in a fluorescent tube, at different distances from the extremely star in the centre of the nebula. The outer colour is red as at that distance only hydrogen gas is excited.

IC 1296 – identified by astrometry.net on the image – is a distant and faint galaxy that is just visible as a faint smudge.

The amazing astrometry.net software is available to anyone who takes an astronomical image when they post the image to the astrometry group on Flickr. Go ahead take an image – not hard to do with a modern digital camera if you can get to a dark place – and try it out.

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