Kodak Astro Zoom AZ651 has a 21.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Nikon S8000 has a 14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Expeed C2 processor.
Kodak Astro Zoom AZ651's sensor provides 7MP more than Nikon S8000's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the Astro Zoom AZ651 and S8000 sensor size comparison.
Kodak Astro Zoom AZ651 and Nikon S8000 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Nikon S8000 has 44% larger pixel area (2.01µm2 vs 1.39µm2) compared to Kodak Astro Zoom AZ651, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.