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The deep sky

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Astrophotography is a specialized type of photography that involves recording images of celestial bodies and large areas of the night sky. It is a branch of photography that, although it has a strong aesthetic and artistic focus, that often contributes in a valuable way with science.
The images are authored by amateur photographer Duarte Silva, a native of Gaula, who belongs to the Association of Amateurs Astronomers of Madeira, a fan and patient image collector of the celestial space who was already been distinguished by NASA. The "Astrophotography" exhibition is at the House of Culture of Santa Cruz, under the "Earth Hour", with the aim of sensitizing the population to environmental issues and the consequent, sustainability of our planet.

How did your passion for the stars begin?
Duarte Silva: This started many years ago, I bought telescopes to see planets. After looking at both the planets and the constellations, I endlessly desire to record them, for example, if you take a trip to London, you take a camera and capture those moments, right? Astrophotography is exactly that. In this field of astrophotography there are two types of processes, the planetary images that are photographs taken in frames, it is a video of two or three minutes from where they can remove more than a thousand frames and after these images are process into a single photograph, who does this type of work is, in my opinion, one of the greatest astronomers in Portugal Paulo Casquinha, he is fantastic and does a job from out of this world! (laughs).

The deep sky, on the other hand, is another type of image, they are photos of galaxies and nebulae, which require 600 minutes of exposure each, if I intend to make 18 images you can imagine the several hours I have to spend to make these photos. The problems for this type of prolonged exposure only arise when, due to the rotation of the earth, satellites appear, space trash, or the rains of shooting stars, when this happens of the 40 images that are made 20 are to throw away.
Let's then address this issue to capture these images in the space what kind of equipment does it require?
DS: These images of the deep sky are outside our solar system, millions of light years away.
But do you know how many light years away?
DS: I can only tell you that Andromeda is 2.5 light years from Earth and is the closest galaxy to our planet.
Then explain to me how you prepare the equipment to capture these images? Do you need to check the weather?

What is the specificity of the equipment?
DS: It is more in the summer that this type of images is made, it must be a very transparent night, that is, if it is not very polluted, if it does not have many dust. From there we set up the telescopes, we make the so-called drift alignment that consists of the assembly of a camera on a telescope that has a motorized equatorial montage, that is, it is a precise and millimetric alignment of the rotation of the earth with the space and the periodic errors of our planet are corrected by the engine. I use special cameras that are only for this type of astrophotography, which is also used in astronomy observatories, one of the equipment makes the alignment with the stars, any millimeter in which the star moves to either the right or the left, taking into account the rotation of the earth, the machine corrects the errors of this trajectory and stays the whole night pointed towards the object that I want to photograph.

Does this mean that if the objective is to photograph the galaxy of Andromeda, for example, the camera always keeps that trajectory all night?
DS: Yes, but there is a detail to take this type of images there are two types of machines, there are DSLR cameras that are Canon and Nikon and others of the sort and then we have the CCD machines dedicated to astronomy that has a problem, are monochromatic, what does this mean? That the images are as black and white as the Hubble telescope does, but to get the actual color in these images we used between 3 to 5 types of filters, which in this case we called RGB for red, green and blue. Thus, we make between 10 and 20 images with the red filter, the same for blue and green, between each of the filters the image is black and white, and the result of this mixture is the actual image we see in the photographs.

You live on an island, so how you get your cameras?
DS: I have friends astronomers on the mainland and friends astrophotographers from whom I learn some techniques and acquiring some material. I know the CCD I use is a professional machine that is seen in the observatories and since in Portugal this type of equipment does not exist for sale we had to send it from abroad, we ordered 10 and it was one for each one of us and they only serve for this purpose, to photograph the deep sky. The material for astronomy is expensive and one of these equipment’s can cost approximately 3, 000 euros.

This is a passion that you only nourish in your free time?
DS: Yes, yes.
You have a profession?
DS: Yes, I only do this when I have time and the weather helps.

Is there an image you would like to capture, but has been difficult?
DS: I'm doing a job now called a mosaic system, what's this? For example, I have a photo of the deep sky with about 200 galaxies, which are the various points that are visualized in the image, if I want to make a mosaic I need six pieces, each image corresponds to 5 to 6 hours of exposure, are several days of work, then the mosaic is embedded and I get a unique brutal image with 2,000 or 3,000 galaxies. For an observatory it is easy to do, they program, and the equipment does everything, now, I do everything myself, whenever there is good weather I have to mount and then disassemble the telescope and it is complicated, because here in Madeira we do not have an observatory.

Is it difficult to get this kind of pictures on the island due to its location or not at all?
DS: No, we here in Madeira and the Canary Islands have an excellent location for this purpose and there is scientific study that proves this. These two outermost regions are the best in Europe in terms of astronomy, so much so that the European Space Agency has one of its observatories set up in the Canaries. In Madeira, two years ago we had renown astronomers making several measurements in Pico do Areeiro and were astounded by the quality of the sky that we have here, in this region there are no factories, that is no great light pollution, except in the more urban areas, such as the Funchal. It is a pity that we cannot take advantage of this aspect, we have the resources and we do not develop them, which is incredible. In Portugal, the general rule is to provide financing to foreigners, and we do not use the resources available in our country. This is a scientific work and in our case is private, the amateurs, develop this type of projects.

But your work has already been recognized by NASA.
DS: Yes, the image of the Rosette nebula was the last work I did, time helped together with the techniques I develop. NASA has asked for my permission to publish this image in an astrophotography magazine, for them it is important to show this kind of photos, from all over the globe, because although this American agency has between 2,000 and 3,000 telescopes, there are billions of galaxies left to photograph. The Rosette nebula was photographed with special filters through the so-called Hubble process, which only let pass a sequence of light. What is a nebula? It is the result of the explosion of a star millions of years ago and it spreads its own gases through space and creates this effect and if I make this same image from 50, 100 or 200 years from now it will be practically the same, there may be one or another star that has exploded, however, but the nebula in general will be identical.

Another image shows the nebula of the horse's head, which was baptized by the detail of what appears to be the head of this animal at the top.

What is the period of summer when you make these images?
DS: It is a period of roughly six months, which begins in May and ends in mid-October. For example, the Orion nebula, which sits on the Orion sword, where the three Marias can be seen, we can see it in Madeira, it is there, the problem is the weather.

And where do you usually photograph?
DS: I photographed all these images at Achada de Gaula, in Santa Cruz, which stands 600 meters high. At the moment we are working in Pico do Areeiro which is about 1,800 meters of high, as part of the Association of Astronomers Amateurs of Madeira we have had some support from the City Council to mount some of our equipment in this place because it is higher and the sky it is cleaner, while in my house in Gaula, which, though it is a high place, to shut the image of the Rosette Nebula I had to do it in two days, one with the red and green filter and the next day the blue and the illuminance, but the joy is there when after all the images are processed and you see the result, you think Epa!

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