Mira Product Brief

Image Registration is the process of aligning images to make features align accurately. Images are registered for the purpose of combining or comparing them, merging RGB channels, or to increase the Signal to Noise ratio. Registration is also an essential step when searching images for transient features and new objects. Mira gives true sub-pixel registration that is unmatched in the quality of the result and ease of use. Truly exceptional results are remarkably simple to obtain.

Although the name is the same, the quality of image registration is not the same from one piece of software to another. All who use it agree that Mira's image registration package is superior in terms of the quality of result and ease of use. Mira can register any number of images of any size, manually or with some automation, and can handle anything from simple offsets to field rotation, non-square pixels, differing image size and scale, and even non-perpendicular axes. So, if your colleague in Timbuktu sends you images taken with a totally different CCD camera, using a different size telescope, and they're rotated 150 degrees and reversed left/right compared with yours, Mira will handle it. A few minutes of processing in Mira and you will have an image set in perfect alignment that you can blink or animate to compare their quality, search for transients, combine for higher signal to noise ratio, or whatever! This degree of capability combined with ease of use is something you see everywhere in Mira.

Using Image Registration to Beat Urban Light Pollution

Although accurate image registration is critical requirement in many types of imaging applications, an example from astronomy illustrates Mira's capabilities very well. A typical problem in astronomy often arises when a telescope does not track well enough to produce sharp images with round stars on long exposures. Yet a long exposure may be required to show to show faint objects or to increase the precision of a measurement to an acceptable level. A long exposure can be synthesized by stacking many shorter exposures in software. However, the images in separate exposures are usually misaligned because of telescope tracking anomalies.  The solution is to acquire many images, then register them after calibration but before combining to make an equivalent single, long exposure image.

Here we show an example of how many short exposures--each of which is virtually worthless--can be combined to produce a usable result. These images were taken through a telescope that tracked very poorly because it was not well aligned with the celestial pole, thus causing field rotation and smeared images. After some experimentation, it was determined that an exposure as long as 30 seconds could be obtained without showing unacceptably elongated stars. Unfortunately, the Signal to Noise ratio of one 30 second image was very poor, thanks to the bright urban sky. Therefore, an exposure long enough to show faint details in this galaxy simply was not an option if the stars were to appear round. The solution was to acquire a number of short 30 second exposures, then register and combine them. Mira's unique image set architecture, efficient image registration and powerful image combining tools turned this hopeless situation into a result that was simply impossible otherwise.

For the processing shown below, Mr. Ray Gralak acquired a series of 30 images of 30 seconds each. The images were opened as an image set and processed to remove CCD artifacts, then registered and combined in Mira. The result shows something very close to what he might have been achieved in a single exposure, had the telescope been able to track sufficiently well. They have been displayed in negative so that you can see the noise and its improvement by the registration and combining processes.