The Aldebaran – Chronicles of the Stars Pilgrim

Conundrum of Astronomy, particularly in South East Asia

Photometry, The Art of Astronomy

Like many subject of sciences, study on astronomy depend on measurement. But, unlike any other branch of science, measurement on astronomy is quiet intricate, since in astronomy, measurement is dealing with the light, per se. In astronomy, object under investigation is the heaven bodies, such as variable stars, minor planets, extra-galaxies, supernovae, or extrasolar planets, as the name for fews contemporary objects in astronomy.

If the objects under investigation is within our grasp, we can measure the length, the weight, the heat, etc. But objects of astronomy are far far beyond our reach, so the question is how do we measure the objects? How far is the object of investigation from us? How old, how hot, how large, how do we know what is that?

Principle technique on measuring the light is coined as the term “photometry”. So, what is photometry anyway? Since the observation of astronomy is merely gathering the information of electromagnetic radiation (light, radio transmission, infra red, x-ray, etc.) from the heaven bodies, so in simplest term, observation of astronomy is gathering the amount of informations, and from the informations we want to derive the well known physical quantities, like size, distance, temperature, structures, etc.

In principle, photometry is straightforward; in practice, there are many subtleties and intricacies that can make headache. But if we want to learn about it, we will find that photometry is an art.

So, how do we do photometry? The term ‘gathering the information of electromagnetic radiation’ means that we have to consider the wavelength dependency. The methods used to perform photometry depend on the wavelength regime under study. Recall the physic on high-school, that we can break the white light into the colors: red, orange, green, blue, etc.

Photometry is dealing with this color separations, called as photometric system. In practice, this system is implemented using set of well-defined passbands, with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard calibrator is provided.

So, we have the ‘colors’, then, we will do the art. As in working of art, an artist always need the tools, such as a painter need the canvas, paints, paint-brush and of course the important thing is the inspiration. So does in astronomy, there is a need for tools and inspiration.

Basically, the equipment in observation of astronomy consists of three major components, that is: collector, analysator and detector. Don’t put these too difficult.

Collector is merely a tool to obtain the data, the simplest form is the telescope. Is not observation of astronomy always dealing with telescope?

Analysator? That is the heart of the art, remember that we are dealing with color? So the analysator can consist of filters to break up the light (if you are working on optical astronomy). There are many kind of method to analysing the informations, but let us make things simple, the choice of analysator is about how do we play with color(s).

Detector? That is the place we put our works, just like the painter need the canvas. For present time, astronomy from amateur level to profesional use CCD as the primary tool, but there are many others option to acquire the data; from Digital SLR to Photomultiplier Photometer. That is depend on technical consideration.

So if the whole component have been set, what next? Just going outside and observe? Well … technically, the answer can be a yes, but, from the art considerations, that is where the inspiration play the role.

Like artist needs inspiration to do the magic, so does the work on astronomy; ask ten astronomers about photometry, then you will have ten answers or even more. But the difference between inspiration of art and astronomy is the approach. Approach of astronomy is based on scientific consideration. There is a need on understanding, what will you do? What is your goal? What is the object you want to observe? After you have your data, what next?

The heaven is so vast with so many bodies to observe and to tinker about, so many options; so one have to start with clear inspirational goal. Name a few objects as inspirational goal, like extrasolar planets,minor-bodies, novae, variable stars – even there are many kind of variable stars to pursue, from day to day variation to years to random variations. The sky is awe and inspiring, and the photometry is an artistic way (with technical difficulties) to describe it. So if you want to pursue the work of photometry, starts with one inspirational object and follow your ‘scientific intuition’ as guidance to decide the observational project you can realistically undertake.

November 14, 2007 - Posted by | Astronomy

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