As any astrophotographer will tell you, the cold nights that are spent out capturing data - whether for a simple DSLR camera nightscape or a multihour deep-sky masterpiece - are only the opening stages of a long journey to produce a final image. An enormous amount of work goes into the processing of even quite a simple data set. We may think of stacking and calibration software programs – like DeepSkyStacker or Nebulosity - when we hear the phrase 'astro-image processing, but often much of this work is done in Photoshop or GIMP too - certainly more than a few final tweaks.
These programs allow you adjust different aspects of an image (like the brightness, contrast and colour balance), but they're also important in another respect, as they are what's known as “layers-based' editors. This means that multiple images, or sets of image data, can be brought into these programs as separate layers.
You can think of regular image-editing programs as being similar to the process of painting, where each daub of new paint is added to the canvas, changing the overall image. But a layers-based editor allows multiple, individual layers to simultaneously combine to make the image on screen. Each of these also can be tweaked, adjusted, masked, aligned or blended in myriad ways while processing.
Because each image layer can be switched on or off, and has different treatments or processing techniques applied to it in isolation, it's easy to vary its contribution to the overall picture, or even delete its effect completely. In the painting analogy this is akin to having the ability to remove, tweak or even change the hue of paint strokes that have already been applied to the canvas.
In a non layers-based editor, to go back and tweak an adjustment to part of the image, like a brightness boost or a curves enhancement, you will often need to restart the editing process, if such alterations are possible in the first place.
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Denne historien er fra May 2022-utgaven av BBC Sky at Night Magazine.
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Could We Find Aliens by Looking for Their Solar Panels?- Designed to reflect ultraviolet and infrared, the panels have a unique fingerprint
Researchers searching for life beyond Earth spend a lot of time thinking about what telltale signs might be detectable astronomically. Forms of unambiguous evidence for the presence of life on another world are known as biosignatures. By extension, techno signatures are indicators of activity by intelligent, civilisation-building life.
Antimatter- In our continuing series, Govert Schilling looks at antimatter, the strange counterpart to most of the matter filling our Universe
Particles and corresponding antiparticles are very much alike, except they have opposite electrical charges. For instance, the antiparticle of the electron - known as the positron - has the same tiny mass, but while electrons carry a negative electrical charge, positrons are positively charged.
Where Have All The Milky Way's Early Stars Gone?- Our Galaxy has a curious lack of pristine stars
The Big Bang produced a Universe filled almost exclusively with hydrogen and helium; all other elements - what astronomers call metals - were produced by stars, supernovae and everything that happens later. So if you can pick out a pristine star with no metals polluting it from among the billions in the Milky Way, then you are likely to have a star dating from our Galaxy's earliest days.
Inside The Sky At Night - Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST
Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST. In July's Sky at Night, we discovered what she's learned since then.
How to stack DSLR data in Siril
Easily combine multiple frames to boost detailin your astro photos
Lunar occultation of Saturn
You'll need to strike a balance on 21 August to capture the Moon covering the ringed planet
How to plot a variable star light curve
A rewarding project to chart stars that change brightness
Smartphone photography with a telescope
Mary Mcintyre explains how to get impressive night-sky images using your phone
Once-a-century solar storm is overdue
If a Carrington Event struck today it would be catastrophic, says Minna Palmroth
The new era of human spaceflight
There's been a step-change in crewed space missions since the dawn of the 21st century. Ben Evans charts its course and looks ahead to future horizons
