I have never really tried to do much stitching. Is there any software to create a panorama for a macro pic?
Could very well be a pipe dream, but worth asking!
Technically any software that is capable of stitching regular photos would be capable of stitching macro photos as well.
However, to be able to accurately stitch photos they need to be taken with little or no parallax (movement of the camera's optical centre). This is typically achieved by rotating the camera/lens about it's optical centre using a "VR" tripod head.
With a regular panorama a shift in the camera's optical centre by a few mm wont have any noticable effect on the results as this is a very small amount compared to the shooting distance. In a macro photograph a few mm is a long way and so any tiny imperfection in the camera rotation will introduce a parallax error. Worse it will likely move the plane of focus by enough to prevent stitching the images.
On account of this unless you have an extremely good reason (like you need to print at a very large size, which brings it's own issues, namely diffraction and depth of field) I wouldn't have thought there's much point in attempting a macro panorama. If you just want a wider field of view, use a wider lens, e.g. swap your 100mm macro lens for a 50mm macro lens.
What is the difference between a panorama for macro compare to (for example) a panorama landscape? I think there is no difference. If your pictures are accurate taken so that you can stitch them, than the motive is not relevant. So panorama for macro is possible.
By the way: thanks for a interesting inspiration to create a macro panorama (+1 for that) ;-).
I would suggest giving it a try with hugin - it has lots of options that other panorama stitchers miss and will allow you to stick an array of photographs rather than panning in one direction only. It also allows you to focus stack which is very handy for macro work. The best bit is the price $0.00 so you have only used up some bandwidth downloading it.
To quote the website:
Although Hugin is essentially a panorama stitcher, like other GUI front-ends it has a range of advanced features: Among the Hugin workflow options, it is possible to correct exposure, Vignetting and White balance between photos; generate HDR, exposure fused or focus stacked output from bracketed photos; or use 16bit and HDR input data natively. Photos can be digital or scanned, and taken with any kind of camera. A full range of lenses are supported, from simple cameraphones to obscure fisheye lenses. Hugin supports various output projections including a range of spherical, cartographic, and camera projections. Hugin supports panoramas taken with multiple rows of photos, with or without bracketing. Bracketed photos can be handheld, taken using a DSLR bracketing function, or as consecutive panoramas shot at different EV exposure levels. Hugin can produce successful panoramas shot with cameras that always shoot using auto-exposure and auto-whitebalance. hugin also supports the use of masks which means that you can exclude parts of images you don't want to appear in your panoramas, or include parts of image you specifically want to appear in your panoramas. Hugin also uses a separate (background) panorama stitcher. This means that you can render a panorama in the PTBatcherGUI stich window, while working on the next panorama in hugin.
It is very possible, and you can even avoid parallax by using a macro rail shifting it parallel to the subject. In this manner you dont rotate the lens around a nodal point.