Got Tricolor Astrophotos on Hypered Techpan? Got a Mac? Maybe you need FilmStar!

What Is It?

After taking some tricolor photos on Techpan film, I could not find an image alignment program for the Mac that could handle them, so I wrote one. This program allows you to see your three monochrome images, pick alignment stars, align, and save the resulting full color image.

The Challenge

Astrophotos taken on Techpan film can be huge, mine are 84 MBytes per channel, and I have not yet made really high res scans. In my experience, these large files choke the image alignment programs designed for CCD images. Typically, the scanned images from film need to be rotated, scaled, and translated to line up with each other. Mac OS X Tiger includes a great image processing library called Core Image that can apply affine transforms to images with great speed and precision. Then a custom Core Image filter is used to combine the three monochrome images into a single full-color 16 bit-per-channel image that can be touched up in Photoshop.


First, scan your Techpan images as 16-bit TIF files. Open them in FilmStar. They will be shown in three panels across the top of the window. Pick three stars. Click on those three stars in each of the three monochrome panels. When you click on a star, the panel zooms in the star allowing you to click precisely in the center of the star. Then hit the Align Images button which will compute the affine transforms to align the green and blue images to the red one, and display the combined full-color image in its own panel. If you like the result, hit Save Combined Image, and a TIF file will be created with the full-color image at the full precision of the originals.


I'm making this program available as shareware. Write me at and I'll send you the latest. I'm very interested in your feedback.

Try Before You Try

Here's the user manual so you can take a look at what the program does and how it does it, to see if it meets your needs.

FilmStar User Manual

Copyright © 2007 by Rick Thurmond

Made on a Macintosh