Tag Archives: observing

Outreach photos with the MAIA CCD camera at the Mercator Telescope

When we go to work at the Mercator Telescope, 20% of the total observing time can be used for our own purposes. In the past this helped me to get additional spectra for my Kepler stars, but it also made it possible for me to help out my collaborators when they needed some extra observations. During my last observing run though, I spent a large portion of this time on making “pretty pictures” with the MAIA camera, resulting in a nice collection of outreach-ready images that the Institute of Astronomy can use in the future for PR. This post is a small how-to guide for making similar images.

1. Planning the observations

To be able to select a suitable target, you need to be familiar with the specifications of the instrument. MAIA is a simultaneous 3 channel frame-transfer CCD camera, meaning that as long as the exposure time is 44 seconds (it takes this long to read out one full frame without using windowing) or longer, it can take exposures continuously and simultaneously in three different channels. It has a chip size of 2k × 3k pixels, and a field of view of 9.4′ × 14.1′, which translates into a resolution of 0.275″/pixel. The three channels are r+i, g, and u (which can be though of as red, green, and blue, and they are labelled as R, G, and U in the system).

To select a target you also need to know the sky. You can use free software like Stellarium to see what objects are visible at a given time and position, just do not forget to actually set your location to the Roque de los Muchachos Observatory (and maybe install my Mercator panorama to really see what you would when standing in front of the observatory building on La Palma). If you want to search in a database, then the one of the Saguaro Astronomy Club is a good resource. You will want a target that is between 3′ and 9′ in size (or larger if you do not want to have the whole object in the field of view). 99% of targets this size will be perfectly suitable for MAIA, so you do not need to worry about their brightness.

You need to avoid bright stars in the field, because using an exposure time of 45 seconds stars that are brighter than 10-11 magnitudes (depending on the seeing conditions) will saturate the CCD and will cause vertical stripes on the final image. You can either use Stellarium, or the desktop client of Aladin to prepare the framing of your image, then record the central coordinate very precisely and use it later on for the pointing of the telescope. The pointing model of MAIA is spot in, so if your coordinate is precise, your target will be in the middle of the frame.

2. Imaging with MAIA

At the beginning of the night you need to take a set of calibration frames for MAIA too, most importantly sky flats. These are standard series, you can pick them from the Scheduler GUI, just pick the month, the time of the day (evening), and leave the default series of 10 U, and 10 R as they are fine like that. Start the sequence when the GUI says that there is ~40 minutes left until the start of the night, then the sky will be dark enough already for the U frames. Do not forget to stop the tracking of the telescope after pointing, this way stars will move across the field and their trails will be thrown out upon calculation a median flat field. You can take bias and dark frames too, or use the prescan area of the CCD to calculate these values (I do this, and for the pretty images, this is definitely satisfactory).

Do these kind of outreach observations preferably when there is a gap in available targets for the actual science programs, so you are not wasting valuable science time. For the object frames set frame transfer on (this puts a lower limit on the exposure time and thus on the brightness of the brightest unsaturated stars as already mentioned earlier, but saves a large amount of time). Focus the telescope. For pretty pictures a good focus is much more important than for time-series photometry! In the Focusing GIU start from thermal focus position minus 0.05 mm, do 3 measurements on both sides with a step of 0.02 mm (larger if seeing is worse), and keep an eye on the images in the ds9 window (use log scaling for better clarity) while the focus sequence is being done. Sometimes the fitted parabola in the GUI is not very precise (especially in U), but during the process you can easily see by eye when the sharpest – most circular – stars were achieved. Set that position in the focus GUI, then unselect the “thermal focus after each pointing” in the Scheduler GUI.

When setting up the exposures, use a series of 4-1-1 for U, G, and R. This means that by setting an exposure time of 45 seconds, you will get one U exposure of 4 × 45 (180) seconds, and four 45 second exposures of G and R each in one exposure repetition. There are some bad columns on the CCD especially in R, so to make life easier I suggest to use dithering, meaning that after a few exposure repetitions you need to move the telescope 3-5″ (or ~1 second) in RA (since the bad columns are along equal RA meridians), and you need to do this at least 2 times for one target. As a result later on when we sync up the frames based on the stars’ positions, the bad columns will not always fall on the same part of the sky, so calculating a median will get rid of them very easily. You do not need to have the guiding on during these observations, as tracking alone is perfectly good enough when the exposure times are so short.

My suggested setup is: 3 exposure groups (dithering of 3-5″ between these) of 5 repetitions each (3 × 5 × 1 U, and 3 × 5 × 4 G, and R frames), which adds up to a total exposure time of 2700 seconds per channel (in 20 and 60 subs of 180 and 45 seconds per channel, respectively). You can use the field rotator for better framing, but do not forget that if you set it to 90 degrees, then dithering needs to be in the declination direction instead of right ascension.

3. Data reduction

When the observations are done, we can start with the data reduction. Just like when working with science data, we first need to calibrate the object frames (to remove artefacts coming from the spatially non constant sensitivity of the CCD chip and dust in front of the detectors). You can do it with your own software/script, or you can simply use a python script I made to automate this step. The only thing you need to remember is that calibration needs to be done channel-by-channel, and that the MAIA fits files always contain three channels, but not always all three are useful. For example during sky flats some files will only contain U channel data, others only G and R. Similarly, object frames will most often only have data in the R and G channels, as only every fourth exposure will contain all three channels (since we set up the exposures this way).

If you want to use my script, just copy all *_FFS.fits and *_OBJ.fits files in the same folder where the reduceMAIA_PR.py file is, and run it in terminal simply by typing “python reduceMAIA_PR.py”. This will create a master flat frame for each channel, and three processed fits files for each OBJ file (one per channel). The script calculates the bias and dark currents from each object file’s prescan area, so it does not need *_BIAS.fits and *_DARK.fits calibration frames. Important note: do not use this script for science data reduction as it is, but use line 164 instead of line 163! I am “cheating” during the flat-fielding of the U channel, long story short, I had to do this to fully remove the remnants of the strong background pattern even at the very low signal level. I have ideas why the proper flat-fielding does not produce fully satisfactory results in the U channel without this “cheat”, but I don’t have time to test it out, and it already works fine enough for the purpose of making pretty images.

Here is a comparison of a raw OBJ frame, the master flat fields, and the calibrated exposures.

4. Image processing

So how do we get to a single colour image from these monochrome frames? The main purpose of taking 60 subs and not a single 2700 second exposure photo was a) lowering the noise, and b) avoiding saturation of the (brighter) stars. We need to integrate these subs (60 or 20, depending on the channel) together, then use the three master channels to create the colour composite. The main difficulty: the optical path to the three CCDs is different, so the stars in the three different channels are at slightly different positions, and it is not a linear transformation to go from one frame to another.

I use AstroPixelProcessor (APP) for the following steps, and since there is a 30 day fully-functional trial version, you can always download it when at the telescope to experiment with it during your observing run. It is a very self-explanatory software package with a good amount of on-line and in-software documentation/help available, so I am only going to summarise the steps of my workflow, instead of going into extensive detail.

Work plan per channel: find star positions (in APP: “Analyse Stars”; for U you should set the sigma to lower if it does not find enough stars), shift and transform images to a common frame (this is to correct for the dithering jumps and guiding shifts, in APP: “Register”; might have to set pattern recognition to triangles if there are too few stars in the frame), integrate separate frames together (in APP: “Integrate”; median for R to get rid of the bad columns, average with simple sigma clipping as outlier rejection for G, and U), save integrated image to a fits file.

Here is the comparison of a single raw image and the integrated image for the R channel.

Work plan with integrated channels: find stars, shift and transform images together (in APP now unselect “same camera and optics”, and possibly select “use dynamic distortion correction”, plus if the number of stars in U is not very high, select the U channel to be the reference frame), save aligned channels one-by-one as fits files.

As an illustration, here are the two other integrated channels too (G and U).

Work plan with fully aligned integrated channels: in APP under “Tools” use the “Combine RGB” button to load in the three files that you saved in the previous step, set the R, G, and U channels to R, G, and B colours, and process to taste. You can play around with the curves, saturation and other settings later in other image processing applications too (e.g., Adobe Lightroom), for this, save the colour image from APP as a 16 bit TIFF file. If you used my python script for the reduction, flip your image vertically to get a true-to-sky orientation.

The rest of the photos I made with the MAIA camera can be seen after the click below (to save bandwidth), or towards the bottom of my flickr album. Continue reading →

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DSLR astrophotography from La Palma

I was lucky enough to get one last observing run at the Mercator Telescope on La Palma, so I spent another eleven nights at the telescope last month, bringing up my totals to 139 nights there (and to 232 overall at international observatories). Since my contract at the Institute of Astronomy ended on the 30th of September, this number will not change anymore :(

Anyway, to make the most out of my last payed trip to the Canaries, I decided that it was time to bring my heavy duty photography equipment with me again, but instead of shooting more time lapse movies, I wanted to do some more serious astrophotography, so I also bought (and then brought along) a compact sized motorised equatorial mount (a Sky-Watcher Sky Adventurer). I mounted the tracking mount on my good old Manfrotto tripod, and used an extra Manfrotto ball head to support and enable easy pointing of my Canon EOS 6D. You can also see the Canon TC-80N3 timer I was using to automate the image acquisition sequence so I did not have to press the shutter release button every two minutes. (Small note: I enabled mirror lock-up and used the 2 second self-timer setting in the camera, so when the TC-80N3 timer gave the signal, the mirror locked up, and 2 seconds later the actual exposure started, eliminating any unwanted vibration from the movement of the mirror. This meant setting an exposure time of 122 seconds on the TC-80N3 timer when I wanted an actual exposure time of 120 seconds.)

While I have done some very basic astrophotography before (and of course time lapse videos), I never had a tracking mount, so I was always limited in terms of exposure time by the Earth’s rotation. Also back then my DSLR was a Canon EOS 7D, that had worse noise levels than my current Canon EOS 6D, which meant that I could not really go above ISO 1600… But now with a better camera, a tracking mount, and a good amount of research before my trip, I was ready to step up my game.

My first few nights were lit by the bright Moon (I arrived just the day after Full Moon), so I spent the short amount of dark time before moonrise to experiment with the mount, my two lenses, and the camera settings. It took me four nights (of very little dark time) to figure everything out, but starting with my 5th night, my camera was outside from the beginning of the astronomical twilight until moonrise (which happened later and later as the days went by). I found out that I prefer taking more zoomed-in photos, so instead of using the Canon 16-35mm f/4 L IS USM lens, I went for the Canon 50mm f/1.4 USM lens. None of these lenses are really made for astrophotography, meaning that wide open they have a pretty bad coma towards the corners of the image on a full frame sensor, therefore I had to stop the lens down to f/4 to get a result that I was happy with. I used ISO 3200 (after reading a lot about ISO levels for astrophotography here), and an exposure time of 120 seconds (to expose the images to a good overall brightness). As a comparison, in 5 to 10 seconds the stars would already move away enough (thanks to Earth’s rotation) that they would appear as short lines instead of circles on the photo without a tracking mount, (see, e.g., my attempt from a few years ago here). After a good polar alignment (which was pretty uncomfortable with such a low mount, but I managed), I had zero issues with the tracking. Even after one hour, there was basically no shift in the stars’ positions, so I was very happy with the whole setup.

To make one picture, I took 30 to 50 120 second exposures of the same spot of the sky (accounting for a total exposure time between 3600 and 6000 seconds), and also ~30 dark and bias frames for proper calibration (no flats since I have no dirt on my sensor, the vignetting at f/4 is negligible, and taking properly illuminated flats with a DSLR is a mess anyway). Then I processed these in AstroPixelProcessor (really great and pretty much self-explanatory software, with a 30 day trial version!), and at the end I saved an average (or median) image to improve the signal to noise ratio of the images. Finally, I used Adobe Lightroom to do some final adjustments mostly on the curves and colour of the photographs. To show how much this process means for the results, here is a comparison of a selected region from a final processed image, and the same area from a single 120 second unprocessed RAW exposure out of the 30 that were used to create it.

It is a quite impressive improvement. I liked doing this so much that I would definitely get more into astrophotography if I did not live under one of the most light polluted skies of the world here in Belgium… :D :( Anyway, below is a selection of the images I made on La Palma, and you can find more on my Flickr (at even higher resolution). Since even these 8 resized to ~50% weight in at ~40 MB, you will have to click after the first one for the rest.

1) The centre of the Milky Way, looking towards Scorpius, Sagittarius, and Ophiuchus, with Saturn in the very centre of the image, and many bright and dark nebulae visible around the field of view. A sum of 30 exposures of 120 seconds each.

Continue reading →

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The past months

It is again the usual situation: I have not written anything here during the past months, but as always, this does not mean that I was not busy with various things basically all the time. So let’s have a short summary – in chronological order.

During November and December I played Uncharted 4 on the PS4, which looked very pretty, but progressed a bit slow for my liking, and the puzzles got quite repetitive after some time. For Christmas I got myself a new helmet (Giro Synthe MIPS) as a present, since my old one was getting way too old. Looks great, feels good. Then we spent two days between the holidays in Holland, visiting ‘s-Hertogenbosch and Nijmegen.

The first day we had sunny weather and Den Bosch was a nice city to walk around, while the next day Nijmegen was grey and cold, but at least we met up with Steven for dinner (and for lunch we also found a great place with delicious healthy sandwiches and drinks). On the next morning I also got the scrape-all-the-ice-off-your-windshield experience for the first time… Although we celebrated New Year’s Eve at home, the night before we went to the Spaans Dak for a fancy dinner, which was nice.

January was even colder than December. After cycling through the freezing fog in -5°C on the last day of the year (my coldest ride ever), I also biked through snow and freezing rain with my MTB during the first days of 2017 (this ride covered me in a layer of ice, and cost me a bit of skin around my left knee), and this kind of weather stayed for the following weeks too. This made January my coldest month on the bike (so far?) with an average ride temperature of 0.6°C (over 875 km in 34.5 hours).

I also got new glasses (my eyes did not get much worse, but my old lenses were so scratched from the years of cleaning that I really needed new ones), so now I have a slightly different look. Being a good citizen, I even went for a Belgian brand (Louis) for the frame. After all these expenses, I decided it was time to save some money, so instead of buying energy bars, I decided to make them myself. I used more or less the recipe from the Global Cycling Network, with some extra ingredients (and twice the amount to fill my baking tin), and the result was delicious. Since then I made a batch (almost 1.5 kg) every month. I also got a brighter front light (Lezyne Power Drive 1100XL) to be able to bike in the dark, therefore I had a few rides well past sunset for the first time ever. At the end of January I sold my MTB because I barely used it, especially since I got the cross bike. So now I have only two bikes again…

I started February with a small meeting in Bern at the International Space Science Institute, discussing the challenges in modelling massive stars. Unluckily around the same time I caught a quite bad cold, and I only recovered a week after coming home from Switzerland. (I felt so weak that I had to turn back from a group ride after 5 kilometres, which was pretty depressing after already not being on the bike for quite some time…). A week later (almost fully recovered by then) I went to the velodrome in Ghent with Willem (and the Belgian Rapha Cycling Club), which was a really fun two hours on the track with 40+ km/h. (Photo: Bert Van Lent – and I am on the far right.)

I wish there was a velodrome in Leuven, it would make my winter cycling training so much easier (and more fun). I had to buy a pair of new wheels for my road bike, because the originals were getting dangerously worn (partly due to the rainy and foggy descents in the Pyrenees last summer where we probably eroded a half millimetre from our rims in two days), and this time I did not go for the usual Mavic choice (although I am mostly happy with those wheels too), but I ordered a wheel-set from a smaller British company: HUNT. I choose their Race Aero wheels (1420g, 28 mm deep, and 22 mm wide rims, £379), and I am fully satisfied with them so far. They are hand built, light, aero, and HUNT offers a 60 day ride and return period, so I can only recommend giving them a try. Should I need a new pair of wheels, I find it likely that I would buy from HUNT again. Thanks to the wider rim, I also switched to a slightly wider tire (moving from 23 mm to 25 mm), and I can definitely feel the difference in ride quality (smoothness) and while cornering. The first ride with the new wheels took me to the French-Belgian border to do a reconnaissance of one of the routes that I had previously prepared for the Squadra Tornado training weekend. That week was great in terms of cycling overall (425 km in 15.5 hours), I even managed one ride in shorts (with knee and arm warmers, but still). Just before the end of the month I also completed the first century of the year too.

In March I started a big project that I always wanted to do; making my own sky atlas. The final push came when I was redoing a few figures about all the observations that had been made with the Mercator telescope since its inauguration (some of which I also compiled into a video), because I realised that I was already using a lot of the tools that would be needed to create a star atlas. Since this is a huge topic I want to write a separate blog entry about it (in the near future), but let me just say that I lost plenty of sleep time since the beginning of March to this project (but it has been always fun and I learned a lot while doing so). I was also a member of a PhD jury for the first time in my life, and I got to wear a fancy gown on the public defence of the candidate. I really liked that :)

For the second half of the month we finally got a spell of nice spring weather, so I returned to the South for the second reconnaissance ride, which was the nicest ride of the season so far (in Belgium). Unluckily the weather for the Tornado outing itself turned out to be pretty rainy, and I also had to drive to Antwerp in the middle of the weekend for an evening, therefore I only made it to the ride on Friday, so at the end I was really happy that I did the recon rides of the two other days earlier. On the PS4 I started playing Horizon Zero Dawn, which seems fun for now (although slightly repetitive). Towards the end of the month I bought a new cycling GPS, the Wahoo ELEMNT Bolt, which is much better than all the Garmins I had before, so I am very happy with the switch.

Unluckily it turns out that my unit has some kind of a hardware issue that only appears around an altitude of 2000 metres (and manifests in huge spikes or a complete loss in elevation data), so when I did my first bike ride from the Observatory on La Palma I had to face some nasty surprises. Of course – being a data scientist nerd – I was not happy about that, but luckily the Wahoo support was very helpful (maybe partly because I provided a detailed, ~5000 character-long description of the issue), and a replacement unit is already on its way as we speak (and as long as I am not crossing the ~2000 metre line I have no issues, so I don’t have to go back to one of my Garmin units in the meantime). Speaking of La Palma: I had an observing run at the Mercator telescope starting on the 4th of April (and lasting 9 nights, bringing my totals there up to 128 nights), then I took a week of holidays on the island just to bike around. The last time I travelled with my bike was in 2013, and most likely this is the last year that I have the opportunity to go to the Canary Islands for work, so I though I had to do it once again. During the nights I spent most of my time working on the sky atlas (drawing the outlines of ~300 dark and bright nebulae by hand) in the control room, and I did a 1.5-2 hour ride from the Observatory before every night (except for a very cold Monday). I have never biked this much up on the mountain. The previous years during the observing runs I only rode the bike between the telescope and the place where we stay during the day, which only added up to 10.5 km (when I rode up to the telescope twice) a day. Now I have a licence so I always drove the car to the telescope which saved a lot of time and energy, therefore I could go for longer rides between starting the instrument calibrations (right after getting out of bed on the afternoon) and having dinner (right before the beginning of the worknight). The weather was also quite nice at 2000 metres. It was almost always sunny, and during the first days it was even so hot that I could just bike in shorts, but a week into my stay I made good use of all the knee/arm warmers and the wind jacket I had with me too…

Normally I would take a taxi down to the hotel in Santa Cruz, but this time I made some arrangements so that I could just bike down, and a taxi would follow me with my bags :) That was quite cool (except for the part where a dog almost jumped at me while I was going down with 60 km/h), and I got an extremely helpful driver (via some local connections) who helped me with my bags a lot. I had six full days to bike, and I managed to bike on each day (which was a first again), although I had to cut a ride much shorter than planned, because I could not sleep anything the night before (thanks to my messed up internal clock). All in all I am happy with what I managed, especially the three longer rides. On the first day I biked around the Southern tip of the island before doing two 2nd category climbs, then after two days of fighting with insomnia I rode around the whole island (a really epic ride of 155 km with 3385 m of elevation gain), while on the last day of my holidays I biked up to the top of the island for the fifth time in my life, but for the first time without stopping.

This climb – leading up to the highest paved point (the Roque de los Muchachos at 2426 metres ASL) of the Canary Islands – is a monster. It is 41.5 km long, it starts at a few metres above sea level and climbs at an average gradient of 6%, but since there is a short downhill/flat section after reaching 2300 metres for the first time, the actual average gradient for the uphill parts is 7% (both for the first ~33 km and the last 3.5 km). Long story short, simply going up and down involves 2750 metres of elevation gain… This specific ride will stay in my memory not only because I finally managed to get up there without stopping, but also because the temperature went from 23°C at sea level to 10°C in the cloud layer (staying between 800 and 1800 metres, but while climbing that was not too cold, even though I was wearing only in shorts), then back up to comfortable (quite warm) levels thanks to the strong sunshine above the clouds.

This was all good until I had to go downhill though the cloud layer, because by that time the clouds became even thicker, so the visibility dropped to ~25 metres, and the temperature to 8°C. This means that I had to descend for a half hour through this layer (and due to the low visibility I had to go relatively slow, so it took me much longer than usual to get down), and I only had an extra gilet with me against the wind, but no jacket or arm warmers against the cold (since although I checked out what the weather situation was at the telescopes before leaving, I did not think about the possibility of having colder temperatures in the cloud layer at lower altitudes – quite stupid of me now that I think of it). With windchill values between 6°C and 2°C that was not a pleasant half hour, and I was shaking slightly by the time I emerged from the cloud layer, but I survived, so it is OK :D In total I biked 783 km in 34.5 hours on La Palma (with an elevation gain of 18140 metres, which explains the horrible average speed).

That afternoon (after warming up in the shower) I even managed to walk down to the new beach which finally opened after years of political games over permits and who knows what else, but now it is open, and it is a great addition to the city (providing not only access to the sea, but also a nice, new view over the colourful houses of the historical seafront with the mountains in the background). Speaking of things other than biking, just after cycling down from the observatory after my observing run, I got to watch two easter processions across the city, and they were both quite an interesting sight. My favourite italian place is luckily still open, so I ate there basically every night (except for one evening when I was so tired/lazy that I just stayed in my room and made spaghetti while watching Netflix). Although I am not a frequent coffee-drinker, I had to check out a place that I had read about in the Guardian a few months ago (El Cafe de Don Manuel). It turnes out that the article was not lying, it is a cosy, calm spot inside a beautiful renovated courtyard with only a few tables, and besides the good coffee, they serve delicious cakes too (one afternoon I simply could not resist taking a second piece, it was so good).

Flying home I got to sit on Business Class for the first time in my life (since for some reason when I booked my tickets to La Palma, this was the cheapest combination for these dates). It was a nice change to have legspace (and incredible amounts of it, especially from Madrid to Brussels) and proper meals, so I did not have to live on sandwiches and chocolates all day long. Of course if you think about it the price difference between business and economy tickets is basically more than what a (three) Michelin starred dinner costs (for two), so I would rather go for that and sit 5 hours without food and legspace if it was about my own hard-earned money. Ridiculous… (And then we are still not talking about First Class tickets on overseas trips.)

It was a bit of a shock to come back to the 7°C and rain, but hopefully from May the weather will finally turn a bit warmer. Besides work, I am also trying to put together a nice non-scientific CV for the corporate world, since soon I will start looking for a new job outside of academia, which will definitely bring some changes into my life.

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Four planets and the Moon over the Mercator telescope

I am back on La Palma (again), supervising our Master students at the telescope (again). Although I did not bring the ‘big guns’ from my photo gear this time, I still have my small camera with me. The first night of this observing run was my 100th night at the Mercator telescope :) To celebrate this, here is a picture I took of the beautiful planetary conjunction before Sunrise on the morning of the 11th with my FUJIFILM X100S camera (with an equivalent focal length of 35 mm) set at f/2.8, at ISO 800, and using an exposure time of 10 seconds.

Although the Moon looks full, it is just a thin crescent (which is better visible after clicking on the image), but the dark side is quite strongly lit by light reflected back from the Earth. This is called earthshine. (At the same moment, Earth looks almost full from the surface of the Moon, so there is a lot of Earthlight even on the dark parts.)

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Summer observing run on La Palma

I am sitting at the airport of La Palma waiting for my hopefully not very delayed flight to Madrid (a bit of delay is ok, but I still want to make it home today), so I have a bit of time to post. I spent the previous almost two weeks (officially 10 nights) working at our Mercator Telescope, and as this time I did not come without my photography equipment, I also took a few nice pictures in my spare time. It has been so long since I took proper pictures here, that I finally had some new ideas and it did not feel like a burden to take photos. So please enjoy the following selection, and should these be not enough, head over to the full gallery on flickr.

Flying to La Palma, if it’s not on a day when charters fly, you will most likely catch a connecting flight in Madrid. I like the colours of this airport a lot. then after landing on La Palma, it’s a one hour taxi ride up from sea level to 2145 meters to the Observatory. The amount of curves along the way is just crazy, so you should keep your eyes on the road…

At the observatory astronomers stay at the residencia. It is basically a small hotel with cozy rooms that can be made totally dark even during daytime (which is pretty much the most important thing when you need to sleep during the day).

This is the first time that I came here at the beginning of the summer, so I finally got to see the sea of yellow flowers on the mountain. Especially in very clear days (so, basically every day here), they are really beautiful against the deep blue backdrop of the sky.

I made an improved version of my famous transparent dome photo, which took a lot of preparations, and running between the control room an the camera. You can read more about the process in my blog post for the old picture.

I was lucky because Venus and Jupiter came unusually close to each other on the evening sky during my stay, so I had something special to put in the background of the telescope (or the building). Note our new simultaneous three channel (hence the three colours on its sides) photometer (MAIA) on the side of the telescope.

I also got to see the laser of the WHT in action. This was actually already the second time that I saw it, but last October I had no camera with me to take pictures. Also, now I could put the Milky Way in the background :)

When I said Venus and Jupiter had a pretty close conjunction, I meant they had an apparent distance less than the diameter of the Moon! It was an amazing visual sight.

Then of course there is the famous caldera of the island, which is usually filled with a sea of clouds, but there are also a few rare days, when you can see down all the way to the bottom.

On one of the last nights I had some fun with light-painting, writing the telescope’s name with a flashlight on a long-exposure image. BTW the rest of the scenery is lit by moonlight.