I have not generally been posting astronomical images on flickr since almost all of them are widely available on other websites. However, I have decided now to post a few which have some special interest or connection with other things that I do.
Number one has to be the Tarantula nebula photographed with the Wide Field Imager on the ESO/MPG 2.2m telescope on La Silla in Chile. The reason I choose this is that it is a spectacular image that took a lot of effort to create. It is also the first astronomical image that I processed using ‘tonemapping’ as applied to multi-exposure High Dynamic Range terrestrial images. The work was done in collaboration with Joao Alves, Benoit Vandame and Yuri Beletski with Benoit doing a great deal of hard work preparing the original filter images in this 2×2 field mosaic (which would encompass 2×2 full Moons) ready for me to combine into a 4-colour image. This combination resulted in an enormous image which, at the time it was done, stretched the capabilities of desktop computers – and took about a week to do!
The image contains a huge range of brightness that needed HDR techniques in order to enable display on a print or a computer screen. This extends from the centre of the stellar cluster in 30 Doradus to the wreaths of dark dust obscuration surrounding the individual nebulae.
Although there are many images of this region taken with different telescopes, including Hubble, this image has somehow become iconic. It has been featured by Apple in the "Inside the Image" series:
and the full-resolution data can be obtained from ESO at:
This region in the Large Magellanic Cloud (about 170,000 light years away) is a huge stellar nursery containing infants (bright green nebulae) to mature teenagers (blue stellar clusters). It also contains the remnant of supernova 1987a – the brightest supernova in several centuries (which I was lucky enough to see with the naked eye when observing on La Silla). This is a real challenge to find and is best seen on the full-resolution image from ESO – although it can be seen on the ‘original’ image here on flickr.
The four filters used to capture the colour information were the usual broad-band B (blue) and V (visible/green) as well as narrow band filters that isolated the green light of glowing oxygen (minus 2 electrons; we call it O^2+ or the [OIII] nebular lines at 496 and 501nm) gas and the red light of hydrogen (Hydrogen-alpha or the first line in the Balmer series: level 3 to 2). The nebulae that are green generally contain hotter, younger stars than the red nebulae.
If I were to choose one other image of this region to look at, it would have to be the wonderful UV-NIR image taken with the new Wide Field Camera 3 (WFC3) on Hubble:
which shows the central R136 cluster in exquisite detail.
Posted by The^Bob on 2012-08-01 07:11:05
Tagged: , astronomy , image , eso , mpg , 2.2m , wfi , b , v , ha , oiii , vandame , alves , beletski , hdr , tonemapped , mosaic , sn1987a , honeycomb , star-clusters , stars , nursery