Sharing photographic adventures

The posts below intend to share an experience, a technique or an idea regarding photography.

A few days ago, I wrote about going out there in the mountains and taking some astrophotographs using a DSLR camera. Now the time has come to process the resulting files using free software. We are going to use Siril as it offers tools for every step I would have thought of in the procedure. The said procedures involves four main steps: converting the RAW files to bitmap files that we can manipulate, align and average the frames to increase the signal to noise ratio, do linear operations like a slight deconvolution, and finally stretch the histogram and apply arbitrary corrections in darktable to edit the image to our taste.

The Milky Way is the galaxy in which our solar system evolves. It contains around 250 billions of stars, a mesmerizing amount. When it comes to visible objects, more than stars it contains dust clouds and nebulae. A simple human eye cannot resolve the position of each individual star composing this giant structure, thus its cloudy appearance and its name, "Milky Way": a white band spanning accross the night sky. If you live in a civilized area, chances are you were never able to truly observe the details of the Galaxy. Too bad, it is a nice sight! It is worth travelling once to a darker area to be able to observe it.

When taking photographs of a dim-lit scene, you could think that choosing the smallest ISO setting on your camera will help with reducing the overall noise of the picture. What matters for real however, is the total number of counts that the sensor has recorded. You cannot change how much light will reach the sensor for a given exposure time and aperture setting, but you can change the way the sensor will count them. This is done precisely by the ISO setting, and finding the range where the handling of the signal is best is an easy procedure.