A Night Under the Milky Way

This photo is a mosaic assembled from 19 of 25 frames taken on a single evening on September 11-12, 1999. A September evening was chosen for this mosaic so that the summer Milky Way could be captured in the early evening and as much of the fall and winter portions of the Milky Way could be photographed as well later in the night.

In 1999 the mosaic was originally manually registered and assembled in Photoshop 4. At that time, computers were much less powerful. The half-resolution mosaic was 300 MB in size and took 20 minutes to just open by Photoshop. The result was unsatisfactory, so project was set aside until recently.

This year (2007), the mosaic was re-done with new scans, taking advantage of a better scanner and better software, as well as the advances in computer speed and hard disk capacity. To assemble the mosaic, a stereographic projection of the Milky Way was plotted in galactic coordinates using the (old) DOS program Deep Space to create a reference map. The individual frames were then registered to the reference map using the program Registar, then manually overlaid in Photoshop CS2.

The resulting file, consisting of 19 frames scanned at 2500 DPI and 12-bit resolution, stored in separate layers, is 1.1 GB in size. At the bottom of the mosaic is the tail of Scorpius, buried in the light pollution of distant San Diego to the southwest of the observing site. The top end extends into Cassiopeia.

Despite the better tools, I suspect I will revisit this project again in the future. Registar could not be used to automatically create the merged mosaic file because it runs out of memory due to the limitations of a 32-bit application running under 32-bit Windows. In addition, I really need to have 4 GB of memory available to Photoshop to handle the large file. It still takes about 5 minutes to open, save, or operate on the image. Of course by the time I get back to this, I will have rephotographed the shot using medium format film so the file will be 4 times larger...

Click on the image to see a larger view of the mosaic