Fill is the length of the galaxy compared with the long side of the frame. Sizes are rounded catalogue values for the visible disk, so a photo usually shows a little less than this. Only galaxies with a known size are listed. Photos: DSS2 via CDS (internet required). Best months are calculated for the Netherlands (52.2°N, 5.3°E).
All photos are shown at the same scale, so you can compare sizes directly.