hello there...
i took sunspot images with my webcam today first time, and decided to make a sun mosaic. u can see it in my latest thread (i only have 5 posts so far at this forum). if u are proficient with gimp or photoshop all you need is single pictures, make a huge canvas like 3333x3333pixel. then add all your single images as separate layers.then create a ring mask and paint out the ringmask with the brush or pen tool about 10pixel thick. now you can align all your images in a ringlike fashion. u will quickly get a catch of it. in the end zoom in 300x and snugly fit all edges to one another. DONE. dont forget to save as TIFF. compression free data !!