Have you ever wondered how telescopes collect the light of the stars to be later analyzed by the astronomers? This new AAO video, entitled Rainbow Fingerprints shows how this is done at the Anglo-Australian Telescope (AAT). The video was produced by AAO Astronomer and Outreach Officer Amanda Bauer, and I have collaborated providing not only the sequences of the AAT outside and inside the dome (which were extracted from my timelapse A 2dF night at the AAT) but also providing comments during the production process.
Video “Rainbow Fingerprints” showing how the light of distant galaxies in collected by the Anglo-Australian Telescope and directed to the AAOmega spectrograph using optical fibres. More information in the AAO webpage Rainbow Fingerprints. Credit: AAO, movie produced by Amanda Bauer (AAO).
The light coming from distant galaxies is first collected using the primary mirror of the telescope, which has a diameter of 4 meters, and then it is sent using optical fibres (the 2dF system) to a dark room where the AAOmega spectrograph is located. This spectrograph, which is a series of special optics, separates the light into its rainbow spectrum, in a similar way a prism separates white light into a rainbow. The separated light is later focussed onto the CCD detector. Finally the video reveals the science quality spectra for two different types of galaxies, one spiral (top panel) and one elliptical (bottom panel), using actual data obtained with the AAT and the AAOmega spectrograph. The information codified in the rainbow fingerprint identifies each galaxy unambiguously: distance, star formation history, chemical composition, age, physical properties as the temperature or the density of the diffuse gas, and many more.
On 16th October 1974, His Royal Highness the Prince of Wales formally opened the 3.9m Anglo-Australian Telescope (AAT, Siding Spring Observatory, NSW, Australia) for scientific operations. Hence the AAT (the telescope where I work) turned 40 last Thursday. We actually had some celebrations and events at the Australian Astronomical Observatory that day, including the release of this wonderful 8 min movie: Steve and the Stars,
The star of the show is Head Telescope Operator, Steve Lee, who has worked at the AAT for almost its entire 40 years of operation. Steve guides this video tour of working with the AAT, exploring how observational techniques have changed from the 1970s to today’s digital age, and the AAT’s exciting future pursuing more world-class discoveries. Famous astrophotographer David Malin co-stars the show. Some material taken from my astronomical time-lapses has been also used for this film.
After the public event for the “AAT 40th Anniversary Celebration” I couldn’t help myself and took this photo with all of us:
Photo taken at the end of the public event for the “AAT 40th Anniversary Celebration”, Thursday 16th Oct 2014. From left to right: Warrick Couch (AAO Director), Steve Lee (Head AAT Operators), Amanda Bauer (AAO Outreach Officer), David Malin (AAO famous astrophotographer) and Andrew Hopkins (Head of AAT Astro Science). Ah, yes, it is also me smiling as a little kid. Credit: Á.R.L.-S.
One of the most complex astronomical instruments nowadays available is the Two Degree Field (2dF) system at the Anglo-Australian Telescope (AAT, Siding Spring Observatory, NSW, Australia). The main part of 2dF is a robot gantry which allows to position up to 400 optical fibers in any object anywhere within a “two degree field” of the sky.
The 2dF instrument attached to the primary focus of the AAT. Note that the mirror of the telescope is opened. This image was chosen to be part of the Stories from Siding Spring Observatory Photo Exhibition the AAO organized last year. Credit: Á.R.L-S.
392 optical fibers are fed to the AAOmega spectrograph, which allows to obtain the full optical spectrum of every object targeted by an optical fiber. The remaining 8 optical fibers are actually fibre-bundles and are used to get an accurate tracking of the telescope while astronomers are observing that field, which may last up to 3 hours. 2dF possesses two field plates: one located at the primary focus of the telescope and another at the position of the robot gantry. While a field is being observed in one plate, 2dF configures the next field on the other plate. A tumbling mechanism is used to exchange the plates. 2dF was designed at the AAO in the late 90s and, since then, it has been used by a large number of international astrophysicists. In a clear night, 2dF can obtain high-quality optical spectroscopic data of more than 2,800 objects.
Indeed, this sophisticated instrument has conducted observations for hundreds of astronomical projects, including galaxy surveys such as the 2dF Galaxy Redshift Survey, the WiggleZ Dark Energy Survey, and the Galaxy And Mass Assembly (GAMA), survey which is still on going and in which I actively participate. The optical fibers of 2dF can be also fed the new HERMES spectrograph, which is now starting the ambitious Galactic Archaeology with HERMES (GALAH) survey at the AAT. GALAH aims to observe around 1 million galactic stars to measure elemental abundances and measure stellar kinematics.
Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The 2dF robot gantry moving and positioning the optical fibers. Credit: Á.R.L-S.
How does 2dF move and position the optical fibers? A very nice way of explain it is using the time-lapse technique, that is, taking many images and then adding all to get a movie of the robot while moving and positioning the fibers. That is why in 2012 I decided to create the video, A 2dF night at the AAT, which assembles 14 time-lapse sequences taken at the AAT during September and November 2011 while I was working at the AAT as support astronomer of the 2dF instrument. Actually, this time-lapse video shows not only how 2dF works but also how the AAT and the dome move and the beauty of the Southern Sky in spring and summer. The time-lapse lasts for 2.9 minutes and combines more than 4000 frames obtained using a CANON EOS 600D provided with a 10-20mm wide-angle lens.
Time-lapse video “A 2dF night at the AAT”. I recommend to follow the link to YouTube and watch it at HD and full screen in a dark room. Credit: Á.R.L-S.
The video consists in three kinds of sequences created at 24 frames per second (fps). The first 3 sequences show how the 2dF robot gantry moves the optical fibers over a plate located at the primary focus of the telescope. Although in real life 2dF needs around 40-45 minutes to configure a full field with 400 fibers, the time-lapse technique allows to speed this process. The first 2 sequences have been assembled taking 1 exposure per second, therefore 1 second of the video corresponds to 24 seconds in real life. The third sequence considers an exposure each 3 seconds, and hence it shows the robot moving very quickly. The next four sequences show the movement of the telescope and the dome. All of them were obtained taking 2 images per second (a second in the movie corresponds to 12 seconds in real life). The long black tube located at the primary focus of the telescope is 2dF. The remaining sequences, all obtained during the night, were created taking exposures of 30 seconds, and hence each second in the video corresponds to 12 minutes in real life.
Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The AAT telescope, with 2dF (the long, black tube) attached at its primary focus, is prepared to start observing. Credit: Á.R.L-S.
Astronomical time-lapse videos allow to see the movement of the Moon, planets and stars in a particular position in the Earth, something that conventional videos cannot achieve. In particular, dim stars and faint sky features, such as the Milky Way with its bright and dark clouds and the Magellanic Clouds, can be now easily recorded. As in my first time-lapse video, The Sky over the AAT, I set the camera up at the beginning of the night, let it run, and check on its progress occasionally. I used at focal of f5.6 and an ISO speed of 1600 ISO for the night sequences.
Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The Magellanic Cloud rise while the Milky Way sets over the Anglo-Australian Telescope at Siding Spring Observatory on 3 Nov 2011. Some kangaroos can be seen in the ground. Credit: Á.R.L-S.
However, the procedure that took more time was processing the hundreds of individual photographies included in each sequence. In many cases, I needed more than 12 hours of computer time, including 3 or 4 iterations per sequence, to get a good combination of low noise and details of the sky, plus “cleaning” bad pixels or cosmic rays. In particular, for this video I tried hard to show the colours of the stars, a detail which is usually lost when increasing the contrast to reveal the faintest stars. In the last sequence of the video, Aldebaran and Betelgeuse appear clearly red, while the stars in the Pleiades and Rigel have a blue color.
Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. A dark night at The Anglo-Australian Telescope (23 Sep 2011). Orion constellation is seen over the AAT dome. The red colour of Alderaban and Betelgeuse and blue colours of Pleiades and Rigel are clearly distinguished. Credit: Á.R.L-S.
As I did for my previous time-lapse, here I also included a sequence which shows the trails created by the stars as they move in the sky as a consequence of the rotation of the Earth. This sequence shows the Celestial Equator and stars at the South (top) and North (bottom) Celestial Hemisphere. Note that star trails have indeed many different colours. Other details that appear in this time-lapse video are clouds moving over the AAT, satellites and airplanes crossing the sky, the nebular emission of the Orion and Carina nebulae, the moonlight entering in the AAT dome, and kangaroos “jumping” in the ground.
Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. Startrails over the Anglo-Australian Telescope on 23 Sep 2011. The colours of the stars are clearly seen in this image, which stacks 1h 6min of observing time. Credit: Á.R.L-S.
Finally, I chose an energetic soundtrack which moves with both 2dF and the sky. It is the theme Blue Raider of the group Epic Soul Factory, by the composer Cesc Villà. Actually, all sequences were created to fit the changes in the music, something that also gave me some headaches. But I think the result was worth all the effort.
A dark winter night, with the Milky Way crossing the firmament while its center in located near the zenith, is one of the most astonishing views we can enjoy. This vision is only obtained from the Southern Hemisphere and it is really inspiring. In particular, the Milky Way shines over the Siding Spring Observatory, near Coonabarabran (NSW), where the famous Anglo-Australian Telescope (AAT) is located. With the idea of sharing the beauty of the night sky to everybody, in May 2011 I decided to start taking timelapse photography while I was working as support astronomer at the AAT. This technique consists on taking many images and then adding all to get a movie with a very high resolution. The best shots I obtained by September 2011 were included in the video The Sky over the Anglo-Australian Telescope, which is available both in YouTube and in several MOV/MP4 files (HD, iPad, iPhone) in my personal AAO webpage.
The video, which lasts for 2.7 minutes, is the results of combining around 3800 different frames obtained using a CANON EOS 600D between June and September 2011. Except for those frames used for the sunset in the first scene, all frames have a 30 seconds exposure time, with a ISO speed of 1600. As the videos were created at 24 fps (frames per second), each second in the movie corresponds to 12 minutes in real time. I used several lens to take the images (standard 50 mm, 50mm x 0.65 focal reducer and a 10 mm wide-angle lens). The focal chosen was 5.6 (for the 50 mm lens) or 4.5 (10 mm wide-angle lens). Processing each sequence of the movie took five to six hours of computer time, and usually I had to repeat this at least once for each sequence, to improve the quality. The soundtrack I chose is an extract of the music Echoes from the past, by the french composer Dj Fab, which gives energy to the timelapse.
The Milky Way is setting at Siding Spring Observatory on 21 Sep 2011. Click here to get the full resolution frame. Credit: Á.R. L-S.
As my main job while I’m at the AAT is providing instrumental and scientific support to the astronomers who are observing in this telescope, I always set the camera up at the beginning of the night, let it run, and check on its progress occasionally. Sometimes this was not easy: wind knocked the camera over on a couple of times, often the battery ran out, and even once I had an encounter with some intransigent kangaroos. However, finally I got this material, which does not only show the magnificent Milky Way rising and setting above the dome of the AAT, but also stars circling the South Celestial Pole, the Magellanic Clouds over the AAT, satellites and airplanes crossing the sky, the Moon rising and setting, and the most famous constellations as Orion, Carina and the Southern Cross.
Circumpolar star traces (2.7 hours) over the Anglo-Australian Telescope on 20 Sep 2011. Click here to get the full resolution frame. Credit: Á.R. L-S.
I hope you enjoy the result. More timelapse videos to come soon!
Last week I shared some of the images I obtained during the Total Solar Eclipse on 13 / 14 November 2012. It was observed from the Mulligan Highway, 44 km south of Lakeland, Queensland Australia. After spending a weekend playing with the raw frames, I ended up with this timelapse video, which shows all the sequence of the eclipse.
Timelapse video of the Total Solar Eclipse on 13 / 14 Nov 2012. The direct link to YouTube is here. Credit: Ángel R. López-Sánchez (Australian Astronomical Observatory / Macquarie University, Agrupación Astronómica de Córdoba / Red Andaluza de Astronomía).
The video combines 1203 individual frames obtained while the eclipse was happening. As before, I used my refractor Skywatcher telescope, 80 mm aperture and 600 mm focal, and my digital camera CANON EOS 600D at primary focus. For all partial phases but the totality I used a solar filter which blocks the 99.9997% of the incident light. The approximate field of view of the video is 2ºx1º. I usually took a frame each 6 seconds, but sometimes I triggered many consecutive images to improve the quality of the final photo of that moment. The music is the theme “WorldBuilder” written by Fran Solo and included in Epic Soul Factory Xpansion Edition.
A/Prof. Ángel R. López-Sánchez 