Astrophotography

Many people love pictures

This is a philosophical problem: epistemology refers to this – in my opinion, exaggeratedly [note SMH 2005] – as the ‘pictorial turn’. Basically, however, communicating with pictures has been common practice for centuries all over the world and is not at all an innovation of postmodernism (as some philosophers believe – let’s leave them to it, maybe they had bad teachers 🙁 ).

People also like to depict the starry sky. You can either stage it romantically – which can be done with fairly simple means – or use all the tools of digital photography to depict it so objectively that scientific insights can be gained from it.

1. We explain how to evaluate images scientifically correctly on a subpage.
2. Simple telescope photos of bright celestial bodies such as planets, which can be easily taken with school and amateur equipment, are already possible with a webcam. We also show and sketch this on a subpage.

Mood photos can be taken in almost any weather and even during a full moon. During a holiday trip through Spain, for example, I simply placed my digital camera on the roof of my rental car during a night-time break and exposed the constellation Sagittarius for 30 seconds. The rising full moon illuminated the rock (with sunlight, which is why it looks like daytime) and the passing clouds hardly interfere, but rather enliven the image in a more natural way: These images have not been edited and therefore show the original colours.

How does a Camera work?

Film was more complicated, but digital cameras work very simply: a chip is a matrix (table) of light-sensitive cells. Each cell reacts to photons as soon as the camera shutter is opened by the shutter release. [Note: If you don’t know how this works in detail, find out more about the photoelectric effect.

Electronics then read how much light has reached each cell. This produces a black-and-white image. If you want colour images, some of the cells are covered with red filters, some with blue filters and some with green filters. Since the cells (pixels) are very small, they still work even if a few neighbouring cells are combined to form a single image point (pixel binning). This is why you can take true-colour images with black-and-white-sensitive photocells that have been fitted with filters.

Photography literally means ‘drawing with light,’ an art form with only about 150 years of tradition. Modern cameras are based on the CCD technology described above, making them ‘charge-coupled devices’ (electronic devices).

Some very creative teacher training students conducted an experiment to demonstrate this:

Resolution

They filled two fields with photocells at different densities. The field was evenly illuminated with different light sources (daylight, LED torch, halogen lamp). The incident light also triggers electrons (charge carriers) in a photocell n (as enlarged pixels). The more light that shines in, the more charge carriers are triggered.

A First Practical Training

When you record a film with a webcam, it consists of numerous individual images (stills). You can now add all these individual images together and even discard the poor ones (e.g. those blurred by the wind). This gives you a single image from a film (motion pictures) that is significantly better – i.e. sharper and richer in contrast – than the poor individual images in the film.

Some Documentary Images