Introduction

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.

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

Hardware (minimum requirements)

To process large images a powerfull computer (>2GHz; Mac G5) with 512Mb memory or more is needed.

Software

Main program

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.

• Categories
  Are just a convenient way of grouping plugins into similar groups.
  In AstroStack 3 there five categories or groups:
  
  • Acquire: get images as files, video frames or from a captured stream.
  • PreProcess: perform some processing on these raw images.
  • Align&Stack: the main process of combining many images into one.
  • PostProcess: perform some processing on the combined, improved picture
  • Store: save the result on disk.
• Plugins
  Plugins are independent parts that are connected together. They have an input and an output.
  Images flow from one plugin to another and each plugin performs some operation on the image.
  Normally plugins will just 'sit' and do nothing until an image is ready at their input.
  Then they will do the necessary processing and push the processed image to the next plugin.
  
  

Menu

Menus:

• File
  New Project : make a new project (loads default.apf)
  Open Project : open a project (load *.apf files)
  Save Project : save project as apf file
  Close Project : close project
  
• Project
  Organize : Open dialog to add and remove plugins in this project
  
• Window
  Restore default : Default position and size of monitors and program
  Dock monitors : position the monitors close to the main program window
  Load size/position : Load the last saved size and position
  Save size/position : Save the size and position of monitors and console
  Crossplatform Look&Feel : Same generic look on all platforms (win/lin/mac)
  Motif Look&Feel : Unix look
  System Look&Feel : Mimics the look of the current platform
  1. Project «projectname» List of open projects
  

Projects

Organize

** 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!

Categories

Acquire

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.

Align&Stack

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.

Store

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

General

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)

FileList (category Acquire)

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.

• Build filelist Select files (e.g. from hardisk) you want to process. They will be displayed in the file list. If you have load plugins for different formats, you can put imagefiles with those formats in the list.
• Load selected file When a file in the list is selected, this will send the filename to next Load plugins where it will actually be loaded and processed further.
• Load whole list Send the whole file list (of names) to the next load plugins for loading and processing.

Load JPG, GIF, PNG (category Acquire)

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.

• Load image Load a single image.
• No color Load image as grayscale.

Brightness Contrast (category PreProcess, PostProcess)

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.

• Brightness Set brightness of an image. [0=darkest, 50=neutral(no change) 100=lightest].
• Contrast Set contrast of an image. [0=darkest, 50=neutral(no change) 100=lightest].
• Reset Set brightness and contrast to neutral position (50/50).

DarkFrame, FlatField correction (category PreProcess)

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.

• Load Flatfield Load a flatfield image . Must be equal sized to main image.
• Use Flatfield Use the flatfield image, if loaded.
• Load Darkframe Load a darkframe image . Must be equal sized to main image.
• Use Darkframe Use the darkframe image, if loaded.
• Load Biasframe Load a biasframe image . Must be equal sized to main image. (full edition only)
• Use Biasframe Use the biasframe image, if loaded.(full edition only)

Align (category Align&Stack)

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).

• None, Min, Max, Center, Track&Hold Coarse alignment. PreCalculate difference in images, based on minimum, maximum image values or center gravity point. Especially Center can give good estimates of alignment with objects like planets.
  Track&Hold is very usefull when you have an object moving along the image (like when you have a non-motorized system). You will have to draw a large enough ROI encompassing all positions of the object, in the series of images you align and stack.
• Move, Rotate Precisely align one image against another by moving and/or rotating it. Rotation center is the centerpoint of the ROI (small cross).
• Quality (full edition only)
  Calculates a quality measure for each image after alignment. Can be used at the stacking phase to sort out the best images of a whole list.
• Select image Load an image to which the other images are to be aligned against.
• Autostart (full edition only)
  When you use 'Select image' and autostart is enabled, the alignment process will start automatically. Sometimes this is not desired and you first want to go back to FileList to try out one or two images manually.

Stack (category Align&Stack)

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.

• Quality threshold (full edition only)
  Uses the quality calculated at the align stage, to sort out the best images of the whole list.
  Only images that have a better quality than the current setting will pass the stacking phase. So setting the sliderknob to the utmost left position will pass all images, setting it to the right position will pass images with maximum quality only.
  
• Reset (full edition only)
  Reset and then perform a full align: this will update the quality threshold bar to contain the lowest and highest quality measured among all aligned images..

Combine (category Align&Stack)

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

• Add images (full edition only)
  Add images instead of combining them and taking their mean value. Can be usefull with very dark images (Deep Sky) and in combination with DDP plugin.

Unsharp masking (category PreProcess, PostProcess)

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.

• Size A low setting will sharpen small details. A higher setting will have effect on a larger area around each pixel.
• Strength The higher the setting the stronger the effect. Overdoing this will make images look unnatural.
  Note: 1=neutral (no change), 0=soften the image (higher size setting will give more blurring).

Filename generator (category Store)

Construct a filename to be used in subsequent save plugins.

• FileName A filename you want to use (instead of the original name).
• Original Use original filename and file date and time.
• Date / Time Use date and/or time in the filename. If original is unchecked the current computer date/time will be used.
• AutoNr Use an auto increment number.
• Example This shows the fully constructed name that will be sent to save plugins.

Save JPG (category Store)

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.

• Select filename / directory Select a file and /or directory you want saved files to be placed in.
  - TIP: First set the filename/directory and then perform the processing -
• Quality Set the JPG quality. Lower quality settings will give small filesizes. Setting 'high' is a good compromise between quality and filesize. If you don't care about filesize, set the slider to 'best'.

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.
   
   
   
   
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).
   
   
   
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.
   
   
   
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.
   
   
   
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.
   
   
   
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.
   
   
7. Notes
   
   • Increasing the ROI will also increase processing time.
   • In the Align plugin: when you select another image to align against, you will be able to follow the alignment process when 'show' is selected.
   • You do not have to turn off preview, because each time you press 'Load whole list' in the File List plugin the sharpening will work on the whole image.