The best, absolutely best stitching/ mosaic software available is AutoPanoGiga. TThis is the link.
http://www.kolor.com/image-stitching...pano-giga.html
I have created panoramas and mosaics using up to 90 overlaping images and there is nothing that i have seen that compares. Photoshop cannot do anywhere near as good a job as this software. Autopano-giga is a dedicated panorama creating program.
Autopano-giga locates matching pixel patters on each individual overlapping image. You do not have to even number the sequence of images it looks for matching overlapping information.
The software will build a multi row panorama from your images automatically. All you need to do is set a few parameters and locate your images and let the software do the rest of the job ( go and have a glass of wine it is memory intensive). It will even colour balance each image and adjust images so that the final mosaic has an even colour balance accross the entire image. The software even has a stacking function for astro images
This software is not cheap and is industry standard. Check it out.
Regards
carl