VLTI School Notes (republished)

After major reorganisation of my home page I managed to delete many unwanted posts but there are the ones which might prove to be useful not only for me but for some others.

With this post I republish my notes from the “Observation and Data Reduction with the Very Large Telescope Interferometer” held in Goutelas Castle, France in 4th of June 2006. I’ve participated on that school with a great pleasure (not only for French wine and cheese).


I’m already at the VLTI School as it was planned, and everything seams to be quite smooth. The organising of the School is quite nice and I do get that feeling of being a student, learning from scratch. Yesterday we traveled quite a long distance and finally in the evening reached to Goutelas. Place is pleasant with a nice nature view.

Lectures during this morning were especially interesting and I learned quite a bit of theory behind the Interferometric concepts. I started to realise that all that experiments back in University Physics lab where actually on purpose and today I could rise my hand and say I also did that experiment during my studies.

First lecture was about The theory of interferometry given by Chris Haniff from Cambridge(UK). From the title one could assume that it must be quite hard to understand, but surprisingly it was quite comprehensive and it was made to grasp the subject! I liked the presentation a lot and would go back to lecture file many times. Thanks a lot Dr. Haniff!

The following lectures were again quite well presented and helped us (OK me, actually) to start getting the first taste of Interferometry as a tool to do some kind of observations better.

Following practical session, gave us an idea about what to expect from Interferometric observations and how to understand them by fitting a model. In fact, that bit normally should come first, you do the model of your object and try to represent it in an easy Fourier convertible bits and then prepare for observations and what you are expecting from them by using already transformed picture. Cool!

Then there was a talk by Paulo Garcia about presentational skills and what to do and what not to do during the presentation. I really liked that talk and I’m going to get hold of his PPT file soon.

Today’s session ended by the talk P. Kervella about star Achernar observed by VINCI Interferometric system. Now that, was really interesting since we got all the basics before in the practical session and that clear representation of the techniques was quite comprehensible. The talk contained very interesting results about Achernar especially they seams to observe the wind coming out from the pols of the star – Really interesting and promising!

So, the day was a success, let’s see what brings tomorrow.


Well, I made a point for myself to post here about every day at the VLTI School on Interferometry. This way I can keep track of things myself and try to summarize the particular day.

Today we had pretty much similar experience started with magnificent talk given by Chris Haniff about The Interferometry in Practice. I must admit that things are quite interesting but relatively hard to grasp. The second talk was by Ségransan about the Observability and UV coverage of Sources followed by afternoon Practical Learning time where we tried our best to do some UV coverage play using different VLTI telescope configurations. It was quite interesting and useful to understand how is the planning for interferometric observations really done … and I though that I do a lot of preparations for NIR observations in one telescope case.

During the evening lecture session Paulo Garcia gave another very useful talk on Scientific Writing Skills which pretty much put all the things in the right order in my mind.

Then we had a nice dinner and drank a lot of French wine during a very tantalizing conversation about astronomical meanings in the calendars of Maya and Armenians. It seams there are quite a few similarities …

OK, till tomorrow.


Today we had quite an interesting day as well – full of new knowledge. In the beginning we had regular lecture but this time by John Monnier who explained us the importance of Phases in Interferometry. Every time when I hear something new during this Summer School is like discovering a treasure and this lecture was particularly like that. It seams that even though your amplitude information can be poor but the phase coverage can give you pretty much everything about your object. During the second lecture by John Monnier we learned how to extract the information from the Phases.

After the lunch we had again Practicals Session on how to Prepare your observations using the ASPRO and ESO soft. Was quite an interesting process full of personal discoveries and learning.

Then Pulo Garcia gave another of his lecture series dedicated on Preparing an ESO/VLTI proposal for observing. The talk was based on the ESO proposal, but it addressed quite a broad range of questions and gave some directions on how to prepare the observing proposals. Very useful talk full of examples and comments from audience members.

The last talk of the day was actually very illuminating for me. It was about the detection of the winds from Herbig Ae/Be type stars with an instrument on VLTI called AMBER. The results were interesting not only from scientific point of view, but also from the instrumental/capability point of view. There will be an improvement on that instrument in the future, which could enable me to use it for study of my faint YSOs – let’s see…

The dinner was funny … we had an artichoke (whole), which I was piling to find the central “source”. Then there was a celebration party of one of the School participant from Belgium and we had a chance to sample some of the types of the Belgian beer.
So far, so good …


Things are getting better and better by every day of the School. We learn a lot of new exiting details about VLTI.

Today we’ve started with the lecture given by Fabien Malbet on Adverse effects, which can totally destroy your observations and one should have pretty good idea about them in order to succeed in getting out the science data. It seams that a very little vibration of the telescope caused by cooling systems can cause the fringes to blare in the best case. He also showed us the example on how sound waves can cause vibrations of the mirrors of the telescope – they actually switched on the music and recorded the vibrations of the mirror and you could listen pretty clear what composition was that. These adverse effects are quite crucial, but ESO team works very hard to get that fixed.

Then, during the second lecture we learned about the calibrator stars, their importance and the ways how to find the. The problem appears to be quite serious when you try to observe quite bright star (say magnitude of 0.5), since your calibrator star should be almost the same magnitude or somewhere in the same magnitude range. There are only very few of them known at the moment, so to observe a calibrator you tend to move away from your objects by several degrees. But when your target is fainter then the situation becomes better, since there are far more stars available for observing in that magnitude range.

After lunch we continued our quest in finding a calibrator star for Achernar star in the Practice Session. This time we used the web-based interface in contrast to previous days where we were using the local software (ASPRO) installed on Linux Laptops with a French keyboard layout.

Then we had another very useful lecture by Paulo Garcia on Professional ethics issues, which gradually passed to open discussion. Everybody spoke and we also got quite useful input from more senior scientists.

This all was followed by poster session where everybody was given 1 minute to present his/her poster to audience and I also did my best in explain my bit.

Getting there, getting there …


I left my blogging during this two days due to this influenza … but I’m not the only one here. We are sitting in the closed room and if someone had in the beginning then it took just one session for the virus to spread. Any way things are improving already, I feel better enough for the forthcoming week of the Summer School.

Now, let’s get on with the real science. I left my blogging on Friday the 8th and that day we were given Personal Project to work on. Every one was to choose an object which he/she would think makes sense to observe with the VLTI and we would then proceed with the real preparations of the proposal and we would check the feasibility of it.

I started the project of YSO in RhoOph to be observed with AMBER or MIDI, but very quick I realised that it’s impossible due to the apparent fact that there are no visible sources around to which the adaptive optics could lock on. Moreover the object itself was quite week for the current configuration of AMBER, but it would actually be good for MIDI. There were other constrains as well which prevented me in choosing any of my favourite objects. So in the end I was left with nothing and the prospect of joining some group was not the best thing, since the people already started the work. But all this was nothing compared to my health, which was quite bad that time. Any way, I joined to some group and tried my best to help somehow, but in the end we dropped all our attempts since there were huge uncertainties on the model predictions.

Next day (9th of June) in the afternoon people started to present their work of preparation. It was quite informative and interesting and I learned many nice ideas, though I couldn’t listen to every single presentation.
Today (10th of June) we went to the nearest castle the name of which I can’t recall. In the beginning it was nice and we walked about 15km on quite a steep roads, but then in the end it was sort of tiring probably because I’m not used to do that kind of walking any more – what a pity circumstance 😉

So, at the moment I’m relaxed and anxious for the next week’s presentations!


Whole Monday was dedicated to MIDI instrument. It’s quite remarkable how complex can instrumentation become and yet you end up with an information which you should interpret with a model fit.

In the morning we had a lecture in basics of Interferometric data reduction by Guy Perrin, where we learned about all the necessary tricks to go through in order to obtain a result applicable for scientific interpretation. Luckily all that steps are done by using already workable pipelines!

Then all the consecutive lectures and practice sessions were presented by Olivier Chesneau. We first learned how MIDI data reductions should be done and what are the pitfalls there to be aware of. Then after the lunch we had practice Session on real data reduction from MIDI on AB Auriga star observations. I must admit that the whole process was quite well presented and prepared. By the end of the day we could proceed through all the steps using MIA package written in IDL and specially prepared to reduce the data from MIDI.

It’s remarkable how this all is starting to make sense. Last week we learned a lot of theory on Interferometry and now we start to get our hands “dirty” with the actual interferometric data. Well done organisers!


Let’s look back now when the school has finished and most of us are back to our daily work schedule. It was very well organised and I learned tons and tons of new things. It’s still an open question if I can really use learned techniques in my current research, but one thing is clear VLTI capabilities are improving and in several years we can be as comfortable as with the single dish telescopes … well, almost 🙂

Last days in the school were full of different useful lectures and practice sessions which helped us to understand the current problems and advancements in the Optical, NIR and Mid-Infrared Interferometry:

Day 8 was full of examples on how the MIDI and AMBER are used to probe AGNs and Eta Carina star. Then we spent whole afternoon in learning the data reduction for the results obtained with AMBER instrument.

Day 9 started with the lecture dedicated to Systematic Biases in interferometric measurements presented by Guy Perrin followed by the lecture in Model Fitting. The whole afternoon we tried our hands on model fitting with the software called Yorik (interesting choice of name though).

Day 10 was dedicated to personal projects. The idea was to split into groups and do the whole data reduction and interpretation on the real interferometric data. It was quite useful experience, since when you learn and do some practice sessions on an interferometric data you just follow what lecturers prescribe to do. But in the case of individual projects you start to use the knowledge accumulated during the school on a real data.

Day 11 started with the presentations on the results of individual projects till 11am, when our taxi arrived to take us back to Boen train station for a long trip back home.


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