Free Software for Stacking Star Trail Photos without Gaps

In order to facilitate making gapless star trail photographs as composites from consecutive frames, as discussed in my
free tutorial, I have developed a simple Photoshop script that you can download from this link:

Download star trail stacking script (free!)
Version 0.21 - updated 3/29/2012 - see below for details

Instructions for use:
     1. Unzip the file, it contains a photoshop script (star_trail_stacker_by_floris_v0.X.jsx), instructions, and license
         Note: there are two versions of the script, one preserves the layers, the other outputs a flattened image
     2. Make a directory containing TIF, TIFF, JPG, or JPEG files of all the frames you wish to merge
         They must be named in consecutive order.
         For preparing images follow the instructions in my tutorial for best results, repeated in brief below:
          a. Do a linear conversion of all your raw files: set all of the following values to zero in your raw converter: 
               recovery, fill light, blacks, brightness, contrast, clarity, and set the tone curve to "linear"
          b. Save all your raw files as TIF's in a new directory
     3. Run script star_trail_stacker_by_floris.jsx on your directory using one of these methods:
          a. Double click the file star_trail_stacker_by_floris.jsx (say YES to the dialogue box that opens)
               -- OR --
          b. From Photoshop, click File > Scripts > Browse... and navigate to the file star_trail_stacker_by_floris.jsx
               -- OR --
          c. Copy the directory 'Star_Trail_Stacker_by_Floris' to the Presets/Scripts directory for Photoshop,
              restart Photoshop, and you can run the script from the File menu > Scripts.
     4. Select your directory of TIF files in the dialogue that pops up
     5. Save your merged file!

If you have trouble running the program, please check that you followed the instructions exactly.
If you still have trouble, contact me.

If you have suggestions upon improving the code, please contact me.

Update Log:

3/29/2012: v0.21
     - Fixed bug in comments section

: v0.2
     - Added support for TIFF, JPG, JPEG extensions
     - Added a script that preserves layers
     - Improved instructions