I have the following problem:
The edge of the imagemosaic is not fit well, Im using geoserver imagemosaic tool to serving orthophotos through wms server. Is it a CRS, Bounding Box problem?
Does the data get reprojected? Typically when I reproject raster to a different coordinate system I get black edges like that, because the raster file itself is rectangular, but the area covered by the reprojected data isn't. The black parts are areas of 'nodata'. If it's an issue of the look of the thing, perhaps you can make nodata transparent or white?