AstroStack is a small, easy to use, yet powerful program to enhance pictures made by CCD digital photography or videocapturing.  It's main purpose is to combine a number of pictures (like a stack of cards, hence the name) made from the same object around the same time.
AstroStack 3 introduces a new concept. It has a fixed nr of categories in which so called plugins can be combined. You will be surprised by the possibilities. See more in Tips & Tricks.

AstroStack 3 is completely rewritten and has a different mode of working than Astrostack 2. So please take some time to get to know the program. Read the Main and How it works sections to get an idea of how the program works. Then start trying it out. Later you can come back here to read more about specific plugins. The working example will lead you through a series of steps to successfully load, stack and save a series of Jupiter images.
For running AstroStack with more memory see installation notes.

A PDF version of this manual, with full size graphics, can be downloaded at the products page.

Hardware/software requirements:

Hardware (minimum requirements)
Processor: Intel Pentium (or compatible) 1GHz; Mac G4 1GHz.
RAM: 256 Mbytes
Windows, Linux or Mac.
To process large images a powerfull computer (>2GHz; Mac G5) with 512Mb memory or more is needed.
AstroStack 3 is written in Java.
You will need to have Java installed (the runtime environment JRE).
Most Linux distributions come with Java included. Mac OSX has Java included, but may yet need to be installed.
The newest version of Java (JRE 1.4.2) can be downloaded from Sun at or from Apple.
AstroStack was tested with different Java versions under Windows, Linux and Mac. It should run from Java 1.3 onwards and on all version of Windows, Linux and Mac OSX (and probably OS9).
To install and run: see here

Main program

AstroStack main window

AstroStack 3 program
Actually there are three floating windows, which can be moved and resized independently.

How it works

AstroStack is divided into categories which in turn are divided into plugins.



menu file  menu project  menu window



With AstroStack you can work on multiple projects (with AstroStack LE (the free version) only one project at the time).


project organize

Here you decide which plugins are to be contained in the project and where. The left window shows the plugins that where found on your computer. Selecting a plugin will show a description, including the categories this plugin can belong to.
The right window shows the plugins in the current project.
Add : To add a plugin: point to the plugin to be added in the left window, then point to the category in the right window where it should be added. When they match (the selected plugin belongs of the same category), then you can press the add button.
Remove : select a plugin in the right window and press remove to remove it from the project.
Up/down : select a plugin in the right window and press up / down to change its order within the category.**
** the order of plugins is very important: for example putting stack before align does not make sense, even though it is possible.
NOTE : there is no Cancel button, so all changes are permanent!


Each category contains one or more plugins.


The acquire pane contains all plugins needed to load, capture images.

Pre Process

The preprocess pane is usefull to process raw images before they are to be combined.


The align&stack pane is where the main processing takes place: combining a range of images to one.

Post process

The postprocess pane the combined image is processed before it is being saved.


The store pane is where you will save the endresult(s) to a file.


Every project contains the same general pane. this is where you will see program options, logfile, info, help and a handy project overview (in full version only).

Plugins (standard)

Plugins are dedicated to a specific task. A plugin can be added to one or more categories. Each plugin has an input and an output. They are connected together from 'left to right'. For example the last (most right) plugin of the Acquire category is connected to the first (most left) plugin in PreProcess etcetera.

FileList (category Acquire)

File list plugin

In this plugin you will assemble a list of files that you want to process. It will send the list to subsequent load plugins where the files will actually be loaded and sent towards PreProcess.

Load JPG, GIF, PNG (category Acquire)

Load plugin

Loads image files of type JPG, GIF or PNG (Portable Network Graphics). One image at the time. When this plugin is preceded by a file list plugin it can take filienames frrom the list, load the files and send them to the next plugin.

Brightness Contrast (category PreProcess, PostProcess)

BrightnessContrast plugin

Adjust Brightness and/or Contrast of an image. As you see it can also be put into the postprocess category to change the endresult image.

DarkFrame, FlatField correction (category PreProcess)

Flatfield plugin

Correct incoming image by using Flatfield and Darkframe images. This plugin is not in the standard project, but you can add it by organizing your project (see Projects).
NOTE: In the img/ directory/map are some images to show the effect of this plugin: Load example00.jpg and example01.jpg in the filelist plugin. Use DarkField.jpg and FlatField.jpg with this plugin.

Align (category Align&Stack)

Align plugin

Align the incoming image with another image. This does only the analyzing, the incoming image will not be changed (see Stack). It uses the ROI to calculate the alignment parameters, so setting the ROI can make a difference (see also tips&tricks).

Stack (category Align&Stack)

Stack plugin

Stack the incoming image. Now the image will be changed (moved, rotated) according to the result calculated by the align stage.

New in 3.1 is the possiblity to let image quality determine which images go to the next phase (stack, combine, etc):

  1. Set (enable) quality in the Align plugin
  2. Press Reset in this plugin
  3. Perform an align (start in Align plugin or Filelist plugin)
  4. Go back to this plugin, note how many images where stacked and set the slider e.g. halfway
  5. Perform an align again
  6. Compare the number of stacked images with the last time.
  7. Set the slider to the left for more images to pass (including more lower quality ones), to the right for higher quality images only.

Combine (category Align&Stack)

Combine plugin

Combine the incoming images into one single image. This plugin will just add them up making the result the average of all incoming images.

Unsharp masking (category PreProcess, PostProcess)

UMA plugin

This is one method of sharpening the end result. It improves local contrast around a pixel or area of pixels.
This plugin can also be added to the preprocess stage.

Filename generator (category Store)

Filename plugin

Construct a filename to be used in subsequent save plugins.

Save JPG (category Store)

Save plugin

Save the incoming image as JPG. If there is a filename generator preceding this plugin the selected filename will be replaced by the name constructed in that plugin.

Saving in AstroStack 3 works a bit different than in most programs.

Some AstroStack plugins are passive untill they receive an image from a connected plugin to process. The Save plugin is such a passive plugin.
When it is enabled and a directory and filename is selected, it just waits (for an image to pass by). Now when (a series of) images are loaded or the align plugin is activated, then the processed endresult will be saved.
This may seem an odd way of working, but it actually has a lot of advantages. For example:
- disable the combine plugin and save a series of aligned and stacked images.
- automatic conversion of image formats.
- save the endresult in different formats at the same time.

Working example

How to succesfully stack a series of images.

  1. Load a series of example images (located in /img directory)
    Make sure the Align plugin is disabled for now ('Enable' is unchecked).
    Load images with 'Build filelist'. Use shift or ctrl keys to select multiple images. For now only choose jpg format images.

    File list plugin

  2. Draw a ROI (Region Of Interest) around the subject
    Click with the mouse on the object to create a fixed size ROI (like below). Or press the (left) mouse button while moving the mouse over the object (dragging).
    Monitor 1

  3. Align settings
    Select an image from the same series that you used to build the filelist. This image will be used to align all the others against.
    Align plugin

  4. Align (or Stack) is disabled
    Make sure the Align plugin is disabled ('Enable' is unchecked). Next press the 'Load whole list' button in the File List plugin. All images in the list will be pushed through the plugin chain. If the Align or stack plugin are disabled the images will just be combined into a smeared result.
    Monitor 2

  5. Align and Stack are enabled
    Make sure the Align plugin is enabled ('Enable' is checked). Again press the 'Load whole list' button in the File List plugin. Now the endimage will be sharp.
    Monitor 2

  6. Play around with sharpness settings
    You can play with the settings in Unsharp Mask. When preview is on (checked) then only the ROI area will be affected. UMA plugin

  7. Notes