The field size on
http://www.wikisky.org/ varies.
I find that 112' is good for large objects, 56' is suitable for most objects and 28' for small objects.
When you click on snapshot the image is always 800x800 pixels.
I just started with M86 and looked at all the Messier galaxies in Virgo with wikisky.
It's a great way to spend a cloudy night or moonlit night.
wikisky and sky-map are the same thing.