AviStack by Michael Theusner is yet another great freeware program for processing planetary images. It was originally designed for lunar images, but works with solar and planetary as well.

AviStack 2

AviStack is available in 32-bit and 64-bit Windows versions, as well as for Unix and Mac operating systems.

The great thing for beginners is that AviStack will automatically process a video or series of still images. Adjustment of the automatic parameters and manual processing is also available.

AviStack uses hundreds or thousands of reference points to register and align multiple points in an image to compensate for distortions due to seeing.

For lucky image processing, AviStack performs these main functions:

• Automatically analyses and grades frames to pick out the sharpest ones
• Automatic multi-point alignment aligns features in individual frames
• Automatic stacking of multiple frames to improve the signal-to-noise ratio
• Wavelet sharpening

Automatic Image Processing

• After installing and clicking on the AviStack program icon, you will see the IDL screens which run AviStack.

• Click the AviStack 2 button at the bottom left of the first screen (Figure 1).

• Click the Click to Continue button at the bottom right of the second screen (Figure 2).

Figure 1 - AviStack IDL screen 1

Figure 2 - AviStack IDL screen 2

• The three work boxes of AviStack will now open (Figure 3).

  1. AviStack 2 Main GUI (Graphic User Interface) box

  2. Main image display

  3. Parameters and Settings Processing Tree

Figure 3 - AviStack 2's work boxes

• From the pull-down menus, go to File > Load Movie (Figure 4).

Figure 4 - AviStack 2's Open dialog

• In AviStack's Open Movie dialog box, navigate to the folder with your AVI movie file (Figure 5).

• Click on the Thumbnail tab. (Figure 5).

• Double click on the movie file that you want to process, or single click to select it and click the open button. (Figure 5).

Figure 5 - AviStack Open Movie dialog box

Figure 6 - Movie file loaded for processing.

• At first you won't see the movie file displayed in the main image display box, but its name will be listed in the main box (Figure 6, Number 1). The image will be displayed when you start processing it.

• Go to the Settings pull down menu and select Processing > All Automatic (except post-processing).

• Go to the Settings pull down menu and select View > All 100%.

• Go to the Settings pull down menu and select Update Display > All/

• Click the Process button to begin automatic processing (Figure 6, Number 2)

AviStack will now begin to automatically process your movie file images. The first process will be Frame Alignment (Figure 7).

AviStack Automatic Processing

Figure 7 - the Frame Alignment process

In the Parameters and Settings Processing Tree box you will see the process being applied to the image (Figure 7, Number 1).

The image should now be visible in the image display box (Figure 7, Number 2).

A status bar will also display the progress of the process being applied (Figure 7, Number 3).

Two white boxes will show the points that are being used to calculate the movement between frames for alignment (Figure 6, Number 4).

Above the progress bar will be a series of boxes with information displayed:

• Current frame number / total frames
• Time elapsed
• Time to go
• Total estimated time

After Frame Alignment is finished, AviStack will automatically go on to ROI (Region of Interest) Selection and Set Reference Points. These latter two processes may go by very quickly.

The next process is Quality Analysis . Again you will see a progress bar. Polygons will appear in the image display to indicate the areas that are being analyzed (Figure 8).

Figure 8 - Quality Analysis

The next process is Reference Point Alignment (Figure 9).

Figure 9 - Reference Point Alignment

Here you will see a series of red dots with crosses in the image that indicate the reference points that are being aligned. These red dot / crosses will change position for each frame in the video.

The final process is Frame Stacking (Figure 10).

Figure 10 - Frame Stacking

AviStack will now start putting the final stack together. It first starts out placing pieces of the image like a puzzle, and then continues stacking pieces on top of each other for each alignment point (Figure 10).

Frame Stacking can take the longest processing time. For example, with an Intel Core 2 Quad Q9650 processor with 8 gigabytes of Ram running under 64-bit Windows 7, a thousand frame video takes about 15 minutes for frame stacking.

At the end, an image is produced that has the best data from each frame stacked for each alignment point.

Figure 11 - The final aligned and stacked image.

If you had all automatic image processing checked, the stacked image should now be saved. The image will now disappear from the display because AviStack is finished working on it, but it is still loaded in AviStack and should be listed in the Main GUI box (Figure 3, Number 1). If you have multiple video files loaded and set for automatic processing, AviStack will automatically move on to the next video file and process it.

At this point, I usually take the image into either RegiStax or Images Plus, or Astra Image for sharpening with wavelets because I am more familiar with those programs. But the image can also be sharpened with wavelets in AviStack.

Image Processing

After you have stacked and saved the image as described above, you can perform some sharpening and adjustments.

AviStack started out as a basic multi-point image aligning and stacking program like AutoStakkert! that didn't do any further post processing. But Joe Zawodny added a wavelets sharpening module to AviStack.

To apply wavelet sharpening to an image in AviStack:

• Make sure the image is loaded. If it is not, go to the stacked image and open it with File > Load Images (Post Processing) pull-down menu.

• In the Parameters and Settings processing tree click the plus sign next to Post Processing (Figure 12, Number 1) and click the plus sign next to Wavelets (Figure 12, Number 2).

Figure 12 - Manual Processing Wavelet Sharpening

• Now click Process File in the main GUI window (Figure 12, Number 3). The image should now be displayed.

• Adjust the sliders in the Wavelet Sharpening dialog box. This is mostly a process of trial and error. These sliders are very sensitive, so just small adjustments to start (Figure 12, Number 4).

Figure 13 - Hold your mouse cursor over the image to see a comparison of the stacked image before and after wavelet sharpening.

• After you have finished with the wavelets, you can also adjust levels to change the brightness and contrast of the image.

• When you are done with post processing, Click Ok in the Post Processing Workflow box (Figure 12, Number 5).

• A final dialog box will come up for Saved Process Image - Parameters (Figure 14).

Figure 14 - Saved Process Image - Parameters

Within this processing section you will be able to:

• Rotate the image in 90-degree increments (Figure 14, Number 1).

• Flip the image vertically and horizontally. AviStack seems to mirror reverse images from DSLR videos, so you will need to reverse them manually after processing. Select "Vertical" from the Flipping pull-down menu to correct it (Figure 14, Number 2).

• Extract a maximum, minimum or region of interest (ROI) area (Figure 14, Number 3).

• Select the File Type format for the saved image (Figure 14, Number 4).

  • FITS
  • TIFF
  • PNG
  • JPG

  Save your image as uncompressed data. I recommend TIFF. Note that JPEG is a compressed file format!

• Select the Bit Depth of 8 or 16 bits (Figure 14, Number 5).

• Add a Suffixto the file (here I have added "Wavelets" to indicate that this is the wavelet sharpened file.

• Select a Directory to save the file (Figure 14, Number 7).

• Finally, click the Save button to save the processed image file (Figure 14, Number 8).

AviStack is a very powerful image processing program with a lot of features for manual control that we did not have the space to cover here, but Michael Theusner has an excellent manual for AviStack that you can download.

This tutorial was done with AviStack version 2.0.