Mosaic of the Winter Constellations of Canis Major, Orion and Taurus.

The constellations of Canis Major (the Big Dog), Orion (the Hunter), and Taurus (the Bull) stretch across the winter sky just before the start of dawn in this three picture mosaic composite.

It may look like just the crop from a wide angle photo, but it is much more than that. It is like three high-resolution photos stitched together.

This panorama was made from three separate images. Each part of the panorama is made of a single 2 minute exposure at ISO 1600 taken with a Canon 20Da DSLR camera. An IDAS LPS filter and a Tiffin Fog filter were used on the lens. The images were shot as JPEG originals in the camera. No dark frames were used.

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Panel 1            Panel 2            Panel 3

Hold your mouse cursor over the text descriptions below the image to see each individual panel of the mosaic. Hold your mouse cursor over the image to see the crop of the final image.

1. The four individual images were run through Russell Croman's GradientXTerminator Photoshop Plug-in in CS1 to remove light-pollution gradients and balance the sky background to neutral. This step is crucial in making the panels of the mosaic blend together seamlessly.

2. The images were then aligned and registered in RegiStar. This can also be done in Images Plus. It can be done manually in Photoshop, but it difficult and tedious.

3. A new image canvas was created in Photoshop that was large enough in the horizontal dimension to hold all three panels of the mosaic when they are composited together.

4. Each individual panel was pasted into Photoshop as a layer.

5. Layer masks were created and a gradient fill was used to blend the seams of the panels.

6. The sky background color was adjusted with levels for each panel so that it matched the others. These were minor tweaks because most of this work was done by GradientXTerminator in the first step.

7. Once the mosaic was composited together, it was saved as a Photoshop .psd file so the layers and masks were preserved.

8. The layers were then flattened.

9. The image was cropped to give the maximum area with no missing parts.

10. Final image color adjustments and enhancements were made, just as with a regular image.

Each individual image was approximately 48 mb in 16-bit RGB color. The 16-bit RGB composite file with layers and masks is almost half of a gigabyte. The full-size panorama is 55mb in 8-bit RGB color and is 8911 x 2148 pixels.

There are other software programs that will help make a panorama that you can try:

• Autostitch - a really remarkable program for creating mosaics that automatically aligns, blends and color corrects individual images into a mosaic. It works with astronomical images, but can leave some artifacts. There is a free demo so it is well worth trying.

• Panorama Tools - powerful, free and open-source software, but difficult to use.

• Photoshop's File > Automate > Photomerge, can work depending on the image. It won't cost you anything extra because it is built into Photoshop, so give it a try.

• RegiStar - excellent software for aligning and registering multiple frames for a mosaic, but expensive for what it does.