Align Frames

In the image below you can see what you end up with when you left-click on the shadow of one of Jupiter’s moons in the Select Input page. You get a white edge box that surrounds the area that will be used during registration as a reference. Often its good to choose a fine frame with a good amount of details and a section of the image with more than average contrast. Most of the functions of this page are explained by clicking on the active regions (hotspots) in the image below.

Correlation type
Registax can use two different ways to estimate the best shift between the frames, Cross- correlation and Phase -correlation.  Cross is the default and probably the most usable. Phase correlation uses a different approach and can sometimes work better.

FFT-filter/Quality Estimate
One of the important features of this page is the FFT-filter that allows better registration of the images. Its useage is discussed in more detail at a separate page (See FFT-filter).
The Quality estimate is another important part of the tool, using the FFT-information this setting will give you a possibility to estimate and order the images/frames based on quality. Its usage is sensitive so this also has a separate page (See Quality filter)

Tracking
This option was added to allow the processing of frames where the feature we want to align is moving over the images. Track Object will try to follow the object based on its latest position, Predict track will estimate where the object will be in the next frame. The latter option is especially handy in fast moving objects (See Tracking ).

Auto-optimize
This function only works during optimisation after the alignment. The optimising routine uses the information of the alignment and searches for the best possible shift of the images. This is estimated by comparison of the squared differences between the image and the reference-area. When this difference becomes smaller the alignment is assumed better. The auto-optimize sets the boundary for the optimizer. When the average difference between the runs (all images optimized)  is reduced by less then the % set in auto-optimize the optimizer stops.

Align all
This button will start the alignment process. If auto-optimize is on then the optimisation will also be started.

Align one
This is used to align a single image and inspect the settings of the FFT-filter/Quality filter. See FFT-filter/Quality Filter

Optimize
This button is disabled at startup and can be used after aligning the images when auto-optimize is not set. The button optimizes all images in the sequence only once.

Align & Stack
This is the “sit back and watch” command. You press the button and the program starts to align/optimize and stack the images and after this you will end up at the image processing page.