Doing mosaics is hard work but worth the effort, this one took some time to put together. If your thinking of giving it a try the following will save you a lot of grief.
I used EQMOSAIC part of the EQASCOM free open source software that controls the telescope mount to take the main frames, 6 where needed for the image below.
Each set to make one of the 6 frames was made up of only 5 main shots at an ISO of 1600 and each was 50 seconds long.
These where stacked and deep sky stacker with a set of master darks flats and bias shots to give me 6 final .tiff files to make up the whole image later on.
Next I used Microsoft's ICE image compositor software to put the 6 images together and saved them as a Photoshop file.
That completed, and I must say I was very impressed with how ICE handled the stitching together of the .tiff files, joined the image up very accurately indeed.
Now we move over to Photoshop where the layers palette showed all the single layers of each frame lined up. I then carefully adjusted each frame using levels curves and brighten and contrast until they where as best matched as possible.
Now it was time to use photo shops auto blend tool and selecting 2 layers linked them together and then used auto-blend on them which does an amazing job.
Continue to link and blend together 2 more layers and again until all have been done and then select all the layers together and do one final auto-blend.
The rest is just normal Photoshop processing methods.
So here is the final result of the North American Nebula Mosaic.