Category Archives: Profesional

Astrophotography from Sydney

Article originally written for the AAO’s Newsletter published on 29th June 2021.

During the last year I’ve been setting up my telescope in the backyard to do astrophotography as an amateur astronomer. This has been possible thanks to getting a good mount (Skywatcher AZ-EQ6-Pro) that allows me to do auto-guiding, and using a little but very clever device (it’s a modified Raspberri Pi manufactured by ZWO called “ASIAir”) that allows me to connect mount and cameras (the main camera for astrophotography and the auxiliary camera for auto-guiding) together, being everything controlled using my son’s iPad (who, with only 8 years, has been also helping me with all of this). In the last months I’ve been able to get a process so smooth that I only need 10 minutes for setup (checking polar alignment, guiding, focus) and then the telescope is observing all the night (it will automatically move to a parked position at the end of the run).

My amateur telescope equipment in April 2021
My amateur telescope equipment in the backyard (15 km from Sydney’s centre) ready for astrophotography in April 2021. The telescope is my Skywatcher Black Diamond 80, f=600mm (f/7.5) that I bought for the Transit of Venus 2012. The x0.8 Orion focal reducer is included here. I use the ZWO ASIAir to control the main camera, the mount (Skywatcher AZ-EQ6 Pro) and the guiding system (ASI120MM + Orion 50mm finderscope). The ZWO Filter Wheel has 7 positions with 2” filters (ZWO LBGR filters, Baader 3.5nn H-alpha, Antlia 3nm [O III], and a hand-made dark filter). The main camera is a ZWO 1600MM-Pro, usually set at -20C.

I must confess this has been a lot of fun for me, also for keeping extra busy and awake during the many meetings / workshops in the middle of the night we all are having lately. I’m getting some nice photos, particularly of nebulae, as I’m using some ultra-narrow (3.5nm thickness) H-alpha and [O III] filters. One of my favourite images is the Cat’s Paw nebula, who would have told me just some few years ago I will be able to get such an image with all these details using a 80mm refractor telescope in Sydney!

Fire in the Cat's Paw Nebula
Deep H-alpha image of the Cat’s Paw Nebula (NGC 6334) in Scorpius obtained from my backyard, 15 km from Sydney’s city centre. All the information in my Flickr. Credit: Ángel R. López-Sánchez (AAO-MQ).

Hence, when last May, I was starting to use TAIPAN and observing with this new instrument, I couldn’t help myself…

While Tayyaba and Anthony helped me to get trained for TAIPAN observing, I decided to check if the instrument could be used for observing HII regions in the outskirts of the nearby spiral galaxy M 83, as well as observing the dwarf galaxies in the neighbourhood. Unfortunately this has been hard for the 1.2m UKST because of the faintness of the targets, but at least I got some test data from the central parts of M83 and some dwarf galaxies, including beautiful starburst NGC 5253. 

However, I was thrilled to be using TAIPAN to observe M83 while, at the same time, in my backyard, my small telescope was also observing M 83 to get a new color-image of this galaxy. It was quite exciting and rewarding!

Colour image of M83  and surroundings combining data in B, G, R and Luminosity filters (8 hours in total combining 2 minute exposures). Data taken on 16 and 17 May 2021 while observing with TAIPAN remotely from my home office. This is still work in progress. Credit: Ángel R. López-Sánchez (AAO-MQ).

This image is still work in process, because we need to take usually hundreds of frames in each filter to get a good astronomical image to mitigate the light pollution plus reducing the background noise as much as we can. And, of course, dealing later with the processing of the data (it’s not that hard as it sounds, there is actually some software already available for amateur astronomers that does this very quickly in a very efficient way, even considering darks, flats, offsets and median stacking with different options). Also, I still need to add the H-alpha data in this image to emphasise the star-forming regions in the spiral disk of M 83. Unfortunately, the weather over Sydney during the last weeks has not being very good for astrophotography, but I hope to get the rest of the data soon.

Additionally, on Wednesday 26th May we enjoyed a total lunar eclipse. I took almost 2000 images of the event while I was participating in an online live event with many schools in Spain (8000+ views during the day). The telescope setup in this case was different, as I used my CANON 5D Mark III DSLR as main camera attached to my telescope. But, even though the totality of this lunar eclipse was short (only around 15 minutes), I got a very nice image of the eclipsed moon. For this image I combined the same data independently for getting the stars and the moon, and merged them together later.

Total Lunar Eclipse - 26 May 2021
Total Lunar Eclipse on 26th May 2021. This image combines 50 x 1″ exposures, ISO 800, obtained with my CANON 5D Mark III attached at primary focus of my Skywatcher Black Diamond 80mm f600mm (F/7.5) during the Total Lunar Eclipse on Wednesday 26 May 2021, between 9:00pm and 9:04pm, Sydney local time. Full description and high resolution image here. Credit: Ángel R. López-Sánchez (AAO-MQ).

Video: Understanding the colours of nebulae

Today I’ve released in my YouTube Channel the very first video of a series that seeks to connect professional astrophysics with amateur astronomy and outreach. This video, is entitled “Understanding the colours of the nebulae“, or why square brackets are important when naming metallic transitions in nebulae.

Do you know how profesional astrophysicists and amateur astronomers get vibrant colour images of nebulae? In this video I provide insights of the Physics behind these images. I emphasise why the ionic transitions of metallic elements (i.e., any element that is not hydrogen or helium) in nebulae must be written with brackets, as they are not recombination lines but collisional excited lines, that is, a kind of forbidden lines that only appear in extreme low-density gases because of the collision of ions with free electrons in the gas.

The video includes my subtitles in both English and Spanish.

An extended article about the video will be added here soon.

I hope you like it! And remember:

The threat of Starlink

This is the English adaptation of the article I published in the Spanish science communication website yesterday, Tuesday 4th June 2019, which was an extended version of the article I wrote for my weekly section “Zoco de Astronomía” in Diario Córdoba last Sunday, 2nd June 2019.

If the light reflected by satellites is not limited, the new “satellite constellations” such as Starlink may not only be a problem for the scientific observations of professional astrophysicists and amateur astronomers but they will also induce a loss for our society, as we could have more satellites than stars visible to the naked eye anywhere in the world during several hours during the night.

For generations and generations we human beings have looked to the heavens and left in them our illusions, hopes, aspirations, goals, even searched for our own origins. The contemplation of a completely starry sky awakens all kinds of feelings in the human being, has defined us as people, as cultures and as societies. Being under a sky full of stars on a moonless night is really one of nature’s greatest spectacles we can enjoy. An unique show that, little by little, we are losing.

First it was the light pollution. As cities grew and technology was able to produce electricity cheaply, we began to shine irresponsibly. It is incredible how little aware we are of the problem of light pollution: billions of euros are lost every year around the world illuminating the sky, something that has as ominous consequences the impact on the environment and human health, in addition to erasing at a stroke until 95% of all the stars we could see in the sky. This generation, the one that is growing now, is the first one in all history that has not been able to enjoy a dark starry sky. Sadly, in many large cities of the civilized world children believe that the true color of the night is orange (or blue, after the introduction of the terrible lighting using LEDs).

These days we are starting to be aware of a new threat to enjoy the starry sky. This thread is global, and not local as the light pollution is. After all one “can  escape” from the light pollution, even for a few days, taking refuge in dark places in the middle of the countryside, on the tops of mountains, in the middle of the ocean, on deserted islands or in the middle of the desert. But we could not escape this new threat if it materializes.

On Thursday, May 23, 2019, the US private space company SpaceX , led by the famous Elon Musk , launched a group of 60 satellites in low Earth orbit . This group of satellites is the first of a super satellite complex (also referred to as a “constellation“) known as Starlink . In the next few years, SpaceX has planned many more launches of these individual satellites, perhaps even surpassing 12,000 units in a decade. The goal of Starlink is to get internet service to everyone at a low cost. But these satellites, which have solar panels and metal surfaces, are visible to the naked eye. Since the launch of these 60 Starlink satellites have been seen by hundreds of thousands of people. These sightings have unleashed the controversy: the satellites are much brighter than expected.

(a) Coverage of the Starlink constellation. (b) Starlink satellites. (c) Starlink satellites prior to being released by the second stage of Falcon 9. (d) Image of the group of galaxies NGC 5353 with the diagonal traces of the Starlink satellite group crossing the field of view, as observed on Saturday 25 of May. Credits: (a) Mark Handley, (b, c) Space X (d) Victoria Girgis, Lowell Observatory.

How bright? It depends on the specific moment, but on some occasions they can equal the brightness of the brightest stars, with flashes that exceed the brightness of Sirius, the brightest star in the night sky. There are internet pages and apps that let you know what artificial satellites can be seen from a particular place on a particular night. Searching for the passage of the International Space Station (ISS) is quite common, for example, and usually like everyone. But the problem here is that there would be 12,000 satellites up there: although the space around the Earth is large, it is not so large, and there will always be tens or hundreds of satellites visible at a particular moment of the night. So much that the worst estimations indicate that there might be more satellites moving through the sky than fixed stars that we can see with the naked eye in urban areas.

Some astronomers have tried to make calculations to account for the problem. For example, the Dutch astrophysicist Cees Bassa accounted for only 1,600 satellites (the first phase of the Starlink constellation), estimating that in places with latitudes equal to that of London (52 degrees north) there would always be 84 satellites visible at any time, of which 15 would be easily visible, especially in the summer months when the sun does not fall much over the horizon. The visibility of satellites is worse in the hours close to sunset or sunrise. With 12 thousand satellites he estimated that between 70 and 100 satellites would be visible from any point of the sky for much of the night. Of course, the exact brightness of these satellites once they are in their final orbit is still unknown, but right now it is feared that many of them can be really as bright as the stars that are seen from places with high light pollution.

Graph showing the number of Starlink satellites visible in latitudes of 52º (London). It assumes 7500 satellites at 340 km altitude, with 75 orbital planes, each with 100 satellites. Only satellites that have a height greater than 30º above the horizon are included. The horizontal axis collects the time of day and the vertical axis the day of the year. The green and red stripes show the sunrise and sunset, respectively. The color yellow corresponds to 40 satellites, the color black to 0 satellites. Following this figure there would be an average of 40 satellites illuminated at any time in the hours around twilight, and all night in the months near the summer solstice (June and July). Credit: Cees Bassa.

Amateur astronomers are screaming blue murder. And many professional astrophysicists too. Some have had curious interactions with Elon Musk, who in this case does not seem to be setting a good example because he has helped spread bad information. For example, in a tweet he said that “the ISS looks very bright because they turn on the lights“, something that is completely false because it simply reflects the light of the Sun, just as Starlink’s satellites do.

In addition to the loss of the starry sky to the general public, the large increase in artificial satellites in low Earth orbit is a huge problem no longer to amateur astronomers (they are used to occasionally have “traces” of artificial satellites in their photos, but this is corrected by obtaining many photos and averaging when stacking) but to professional astrophysicists. Astrophysical images are often “deep ” (exposures of many minutes, sometimes an hour) but few (2 – 5 images per target), so the “clean” data would be much more complicated. And to this we have to add that the many calibration images (for example, “flatfields“), that are fundamental for the correct scientific use of the data, would also be affected, and it is necessary to invest more time than is currently used in these shots. calibration to make sure they are valid.

In the coming years new telescopic installations will be inaugurated. Some of them are costing a lot of money and are thought to take images in very large fields of the sky. For example, the Large Synoptic Survey Telescope (LSST) will be capable of mapping the entire sky in only 3 nights. Nonetheless, this early morning LSST has issued a statement notifying that, after a preliminary study, the impact of the satellites of the Starlink constellation would be very small for LSST. That is because the algorithm that combines individual frames (3 of them) into a final scientific image should be able to eliminate the satellite traces.

But it is not only the large telescopes: there are dozens of “modest” professional telescopes (say, between half a meter and 4 meters in size) that perform fundamental scientific work, for example, the hunting of asteroids and comets or the search for supernovas. All these scientific observations would also be affected by satellite traces.

Another problem added: the radio-interference that the satellites would cause in radio telescopes . This is something well known by professionals and difficult to quantify until the satellites are actually there. One of the most ambitious international projects is precisely the SKASquare Kilometer Array“, a network with thousands of radio telescopes that will be installed between South Africa and Australia. If constellations of satellites like Starlink are not careful in limiting the frequencies in which they emit and receive they could greatly limit the huge investment in technical and human capital that is being used in SKA. Several professional radio astronomy organizations, including the NRAO ( National Radio Astronomy Observatory, USA ), have issued statements insisting that SpaceX has been in contact with them to minimize the impact of radio interference on scientific observation, delimiting “exclusion zones“. These are frequency ranges that should not be used in satellites, to minimize the impact on astrophysical tasks from the ground. But this does not have to be the case in constellations of satellites launched by other companies or other countries.

Here we also have to insist on something else: we do not need to go into space for doing astronomy (as indeed Elon Musk himself suggested): many of these installations (telescopes of class 30 meters and radio interferometers such as the SKA) are only possible on Earth, at least with the current means and budgets. In addition, satellites in low orbit also interfere with the work of space telescopes such as the HST ( Hubble Space Telescope )! It is not common yet, but it is detected in some shots of the HST the passage of artificial satellites as “defocused strokes” .

Early this week, the International Astronomical Union (IAU) issued a statement precisely warning of this problem, notifying that “we still do not understand well the impact of thousands of these satellites visible throughout the night sky and, despite their good intentions, these constellations of satellites can threaten [astronomical observations in optical and radio] In the same statement, the IAU asks all the companies involved and legislators to work together with the astronomical community to understand the real impact that satellite constellations may have and thus eliminate or at least mitigate their impact on scientific work and exploration. space.

Indeed, many of us do not expect to suspend these space projects, but we hope that satellite companies take this problem into account, in order to minimize the reflectivity of the satellites and the frequencies in which they operate, and to legislate correctly so that this actually happens. It is no longer just SpaceX: several international companies want to launch their own satellite constellations in the near future, reaching more than 50,000 in just a couple of decades.

In 20 years or so, the children of our world will might see the sky as an orange glow where hundreds of bright spots are continuously moving, losing forever the real beauty of the night sky. And they will not be able to escape from this pollution: it does not matter where you are on Earth, far or near cities, if you’re lost in a desert, in the middle of the ocean or in an astronomical observatory:  there could be dozens or hundreds of satellites moving through the sky almost at any moment. Goodbye to the romanticism of Astronomy and identifying the constellations in the sky. Goodbye to a society and young people marveling at the beauty of a dark sky full of stars. They might get the best internet connection, but they will be losing what once it made us dream with the stars.


My contribution to 2018 #StargazingABC

How can I say it in just few words? It was both very exciting and exhausting, with a little bit of bitter too. But, overall, last week at Siding Spring Observatory was one of the best experiences I have had in a long time working at the telescope, combining science research, amateur astronomy, outreach and science communication during the Stargazing ABC Live shows.

The AAT is ready for #StargazingABC. Hosts Julia Zemiro and Prof Brian Cox are sit in the piano, while Brian still rehearsing. Credit: Ángel R. López-Sánchez.

When I’m writing this, at 6:44pm 30th May 2018, I’m still observing at the Anglo-Australian Telescope. I’m doing it remotely from Sydney. It is my last night in a very long run (18 nights in May) for my own research project, which I will detail here eventually. I’m exhausted and need a good break, body and mind can’t survive this crazy rhythm, sleeping an average of 4-5 hours per day, and without any break during the weekends.

But let me at least quickly mention here my contribution to the 2018 Stargazing Live shows:

1. I provided A LOT OF information about Astronomy and the Anglo-Australian Telescope to the ABC and BBC crews. This is something that I’ve been doing during the last months, and might be considered as part of my role of “AAO Science Communicator Officer”.

2. I provided plenty of astrophotography and video-timelapse material, which was used during the shows. The most important of these is the new timelapse video “Stargazing at Siding Spring Observatory“, that you can enjoy here:

3. I spent some of my scheduled time at the Anglo-Australian Telescope to prepare a nice, new image of a beautiful astronomy object, that was later discussed during the show. It was the planetary nebula NGC 5189, for which I provided extra information in the previous post.

4. But the most important contribution for the show was actually observing with the AAT two transients reported by the citizen scientists who participated in a program to search for type Ia supernova in other galaxies. After confirming that the transient was there, we got spectroscopic information using KOALA+AAOmega, reduced the data, analysed the data, confirmed that both transients were type Ia supernova in distant galaxies, and wrote a science report with the discovery!

This was something I originally didn’t plan to do, but, as I said, it was my own research program that scheduled at the AAT during the StargazingABC, so I decided to do it and it got a reward, as this also allowed us to submit two science reports with the discoveries!

These two nights were really exciting! I really want to thank my friends and colleagues Lluís Galbany and Yago Ascasibar, as well as the AAT Night Assistant Kristin Fiegert (AAO), for their wonderful help in all of this.

The discovery of the transients and the confirmation that they were type Ia supernova in distant galaxies has appeared in many media news these days, including in ABC Science News, and also here: “Citizen scientists find two supernovae and (slightly) revise the age of the cosmos“.

It was also a privilege talking with Prof Brian Cox, who is absolutely great, and even recorded a short video with me for my son. Thank you a lot, Brian!

Prof Brian Cox and me are ready for #StargazingABC.

Where is the “bitter” I mentioned in the first paragraph? Well it is when the credit is not given. And not credit was given to me during the shows. I was still hoping at least having my name in the screen, in an ideal world even participating in person during the shows. But with my name (Ángel) and my strong English accent… well… perhaps in another life… I know what I did and I know how important my contribution was, and as I said I really enjoyed a lot all the time.

I hope I’ll be back if #StargazingABC returns in 2019!

PS: If you are in Australia, you can watch anytime the 3 episodes of 2018 #StargazingABC following this link to the ABC webpages.

Planetary nebula NGC 5189 around WR-like star with the AAT for #StargazingABC

This is the object we observed at the Anglo-Australian Telescope as part of the “Stargazing Live” events at Siding Spring Observatory (NSW, Australia).

We used the APOGEE camera at the AAT Cassegrain focus and took some short exposures in several broad-band filters (B, V, R and I).

The planetary nebular NGC 5189 is located in the constellation of Musca (“The Fly”), near the South Celestial Pole.

The distance to NGC 5189 is around 1780 light-years from Earth, as measured in 2008.

It shows one of the more remarkable complex morphologies among all the known planetary nebulae, with many structures at different scales, indicating that the progenitor star experienced multiple outbursts.

Each outburst had different velocities, inducing shock-waves in the surrounding gas.

The central star is classified as Wolf-Rayet-type [WR] because it is very hot, it shows intense features of helium, carbon and oxygen, and it has very high stellar winds.

The most massive stars undergo the Wolf-Rayet (WR) phase before exploding as supernova, but the central stars of ~10% of planetary nebula also show Wolf-Rayet-type features.

The Wolf-Rayet-type stars in planetary nebulae are much older objects than the “standard” WR stars, as they descend from evolved low-mass stars and not from high-mass stars.

That is why Wolf-Rayet-type stars in planetary nebula are named [WR].

Wolf-Rayet-type stars are closely related to white dwarf stars.

The central Wolf-Rayet-type star in NGC 5189 is a very rare, low-mass (about the mass of the Sun) WO (oxygen-rich) star. Its temperature is 165 000 K and its stellar wind moves at 2500 km/s.

The Wolf-Rayet-type star in NGC 5189 has a companion star of around 0.8 times the mass of our Sun. It needs 4 days to complete an orbit around the [WR] star, as discovered in 2015.

The complex morphology in NGC 5189 seems to be consequence of the interaction between the progenitor of the Wolf-Rayet-type star and its companion star.

In the AAT image, the green color is coming from glowing nitrogen and hydrogen, the blue color from glowing oxygen. The red color is coming from the stellar emission