I'm trying to merge raster tiles that all have the same, but unequal cell size (X: 2,8, Y: 2,9). When I use the Mosaic To New Raster tool, I can enter ONE cell size which either results in a raster shifted in X or Y-direction or a black line going through the resulting raster when I don't specify anything. Is there any way to get around this?
If you don't have to work in an ESRI workflow you can try the gdal merge tool from the GDAL toolset (http://www.gdal.org/gdal_merge.html). I'm pretty sure this will allow you to use floating point numbers for your resolution. I've had trouble with this tool if you are using very large rasters but if they aren't too large it can work well.