Assembling the Mosaic
The first step after acquiring your images for a mosaic is to assemble them in PhotoShop in their initial configuration. I generally open all the images at the same time and do an initial arrangement to make sure everything is going to fit correctly and nothing is missing. The image below shows 3 frames of a Moon image I have taken as they have been initially dropped onto the canvas for processing. This is the image we will work thru in this tutorial.

As can be seen, there are three layers in the image that have been added to the canvas and roughly aligned. It is obvious from this image that they cannot simply be flattened and turned into the final image as there are differences in brightness, hard edges, etc, that must all be taken care of.

The first step is to properly align the images. So long as there is no rotation between the images this is a fairly simple task. But as there often happens to be some rotation, I will step thru how to handle that as well. Thankfully, PhotoShop provides all the tools we need to accomplish these tasks and they are all very simple to use after a bit of practice.

The first thing to do in aligning your images is to select the anchor image, that layer which will be the base for which all other images are aligned. Since I happen to have three images here, I am using the center image as the anchor image for this demonstration. This layer doesn’t necessarily have to be the layer with the brightness you are going to finally have, we will get to that later, just the position for which all other layers will be aligned. Later we will select a base brightness layer for that part of the exercise

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