Dr. Ángel R. López-Sánchez

Postdoc at Australian Astronomical Observatory / Macquarie University

Astronomy & Astrophysics
using multiwavelength data



Rainbow over the Anglo-Australian Telescope in Siding Spring Observatory, NSW, Australia © Á.R.L-S.

Timelapses

A 2dF night at the Anglo-Australian Telescope


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. 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 I decided to create the video, A 2dF night at the AAT, which assembles 14 new time-lapse sequences taken at the AAT. Actually, this new 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. All sequences were taken during September and November 2011 while I was working as support astronomer of the 2dF instrument.


HD (1280 x 720) resolution, MOV format, 208 Mb


Large (960 x 540) resolution, M4V format, 79 Mb (recommended for iPad or similar tablets)


Small (480 x 272) resolution, M4V format, 19 Mb (recommended for iPhone or similar phones)


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.

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 previous 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.

However, the procedure that has taken more time is processing the hundreds of individual photographies included in each sequence. In many cases, I have 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 have 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. As I also did for the previous time-lapse, here I have 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 the new 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. 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 is worth all the effort.


Some still frames from this timelapse


Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

The 2dF robot gantry moving the optical fibers. Click here to get the full resolution frame. © Á.R.L-S.


Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

The AAT telescope, with 2dF (the long, black tube) attached at its primary focus, is prepared to start observing.
Click here to get the full resolution frame. © Á.R.L-S.



Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

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. Click here to get the full resolution frame. © Á.R.L-S.



Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

The Anglo-Australian Telescope observing at night on 5 Nov 2011. Some moonlight is shining into the dome.
Click here to get the full resolution frame. © Á.R.L-S.



Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

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. Click here to get the full resolution frame. © Á.R.L-S.



Timelapse: A 2dF night at the Anglo-Australian Telescope, by Ángel R. López-Sánchez (AAO/MQ)

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.
Click here to get the full resolution frame. © Á.R.L-S.



| Updated: 25.07.2012 | Released: 12.03.2012 |


The Sky over the Anglo-Australian Telescope


All the information concerning my first timelapse video, The sky over the Anglo-Australian Telescope, can be found in this webpage.

| Updated: 25.12.2011 | Released: 29.09.2011 |