Orestis,
I was most impressed with the detail of your observations of NGC 253.
It would not surprise me if you were actually seeing dust lanes in this high surface brightness (by galaxy standards) object. (On perfect nights, I was sometimes able to glimpse the major dust lanes in M31)
I am not certain if the knots and "HII regions" you reported seeing are actually nebulae.
It does seem much more likely to me that, at the very limited angular resolution of the eye's "Rod" detectors (which is what
causes the "fuzzy" appearance of galaxies in the eyepiece), the smallest features that we can visually detect in NGC 253 are likely to be:
- spiral arm segments
- star clouds
- and , perhaps, complexes which contain several giant nebulae together with their embedded clusters and stellar associations.
However, I am prepared to "eat my words", if necessary, as your retina seems to be inordinately sensitive, and perhaps the detectors in your retina that you use for night vision are more closely spaced than they are in other people!!
cheers, bad galaxy man
My impression, from photographs, is that the HII regions evident in NGC 253 are actually small;
hence my comment that they may be beyond the ability of the dark-adapted eye's resolution.
Perhaps it is best to compare our visual observations with a fairly modest photo of this galaxy:
You see what I mean about seeing spiral arm segments and star clouds instead of individual objects within NGC 253?