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
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