In article ,
David Knisely wrote:



I think that you probably did see the sprial structure, as I have seen it in
my own 8 inch Newtonian on a number of occasions (from a dark sky site of
course). It isn't quite as obvious as the structure is in my 10 inch (where
I
can see some of the individual arm segments or the larger star clouds), but
you can easily see it as more than just mottling. One night at my dark-sky
site, I stopped my 10 inch down to 94mm (3.7 inches) to see how M51's
appearance changed. M51 did not show clear spiral structure at that
aperture,
but it did show sort of a diffuse irregular ring-like structure around the
brighter core which was distinct enough from the nuclear region to be quite
noticable. At 80mm, the galaxy looked like a circular fuzzy spot with maybe
just a hint of mottling, a small brighter core, and the companion galaxy next
to it. Below 80mm, all hints of mottling vanished. Last night, I had the
NexStar 9.25GPS on M51, and it was one of the finest views of the galaxy I
have ever had with such an aperture. The arms were dim but quite obvious,
and
the galaxy took even 297x well, although it was better at 168x. The night
was
good enough that I could even glimse the faint connection between M51 and its
companion, along with one of the tidal plumes. Clear skies to you.


One three nights in February 1993, while at Winter Star Party in the
Florida Keys, I could detect both the spiral structure and the bridge
separating M51 and NGC 5195. In all three cases, I was observing by
myself in the early morning hours, when M51 was at altitudes of 60-70
degrees.

Seeing and transparency at the time were excellent, and I spent at least
an hour on only M51. The bridge was a certainty whenever I would let
the companion drift into view first, before the light of M51 could
interfere.

The scope employed was my 6" f/9 AP Starfire, with magnifications of
160X and 190X providing the best views. I have not repeated the
observation with that scope since, although I have also not considered
it a priority. My 18" f/4.5 usually shows the spiral structure quite
easily in a decent sky.

Starry Skies,
Rich