Animation processing: how to turn your astronomy photos into animations

Turn your astro images into animations like this one of Jupiter

Image credit: Steve Marsh

Some bodies in the Solar System change their appearance over very short time-scales. Mars, Jupiter and Saturn fall into this category: their fast rotations drag features on their visible surfaces around their globes at a frenetic pace. The Sun viewed in the hydrogen-alpha wavelength of light is another good example, as here features can change appearance in timescales of minutes or even seconds.

Capturing these changes in a sequence of still images and presenting them in a strip or grid display can show the changes well. However, the images really come to life when they are put together in the form of an animation. This can produce results that far exceed expectations.

There are many ways to produce animated sequences, and many different ways to store them. A popular technique is to produce what’s known as an animated GIF file, GIF being a web-friendly image file format that supports animation.

A movie file is another popular way to bring together still files to show motion. The freeware application Registax will create AVI movie files from processed still images for you. The benefit of using a program like Registax is that it can remove a lot of the hard work you’d otherwise need to do to create a smooth-flowing sequence of aligned frames.

A successful animated sequence starts at the point of capture. Here, you must decide on how many captures you’re aiming for, how frequently you’re going to take them and how long each one is going to be. The answers to these questions are also affected by external factors such as the amount of free space on your hard disk, the highest uncompressed frame rate your camera can achieve, the image scale used (how much the target looks magnified) and the nature of the object or event you’re trying to capture.

A sequence of 30s captures taken at one-minute intervals and covering an hour of rotation on Jupiter will show about a tenth of the planet’s rotation and generate 60 capture files, each 30s long. Processing these files isn’t a job for the faint-hearted, although batch-processing can help – something that the freeware program AVIStack 2 is particularly good at.

Arduous though the task of processing many AVI captures may be, once you have your still frames to hand, the exciting part of creating an animation from them can begin. There are lots of different programs that can be used here, such as AnimateGIF (freeware), Registax itself and various commercial applications. Adobe’s ImageReady package, which used to ship with Photoshop, was particularly good at the task, allowing you to load each frame into a single file as a separate layer. ImageReady was discontinued with Photoshop CS3, but its functionality lives on in later versions as detailed opposite.

Although our basic step-by-step process is based around later versions of Photoshop, the preparation and alignment routines described can be used with any animation program that supports flick-book style animation.
 


STEP BY STEP

How to create a GIF animation from a sequence of planetary captures

STEP 1

Examine each still image in the sequence using a graphics editor, looking for variations in brightness. If necessary, alter overly bright or dim frames so they all show more or less the same general tone.
 
 

STEP 2

Load each frame into a separate layer in the order they were taken, putting the earliest frame at the bottom (layer 1). If there are many frames, name the layers so you can keep track of them all.
 
 

STEP 3

Hide all of the layers apart from 1 and 2. Nudge layer 2 so that common, non-moving features line up. Toggle the visibility of 2 off and on to check the alignment.
 
 

STEP 4

Repeat step 3 for each of the layers above layer 1, using layer 1 as the reference. Finally, crop the image to remove any gaps revealed by the layer alignments.
 
 

STEP 5

Hide all layers except 1. From the main menu, select Window, then
Animation. In animation control, select frame 1 and duplicate using the button shown above. Create the same number of frames as layers.
 
 

STEP 6

Select frame 2 and make layer 2 visible. Repeat for the other frames and layers. Select all frames then set the frame delay as required. Then select File, then Save for Web & Devices, and save as a GIF file.
 

This article is an extract from Part 2 of our series of in-depth guides to image processing techniques. To read the rest of the article, see the February 2012 issue of Sky at Night Magazine

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