A Bear Hunt

Alexander Avtanski wrote:
Hey, last Saturday I was convinced that I'm seeing spiral
structure in M51 in my 8". And that was under much less
than ideal conditions - not very good transparency and some
light pollution.

So, now I have to ask myself: Do I have really good eyes or
really good imagination? :-)

Dunno. It depends on what you mean by "hints of spiral structure." I
think I've seen the spiral structure in my 5-inch SCT, but that may just
mean I set myself a lower bar at the time for "hints" than other people
would. For what it's worth, I would not submit that one as a reliable
observation.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
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Brian Tung says:

I think I've seen the spiral structure in my 5-inch SCT, but that may just
mean I set myself a lower bar at the time for "hints" than other people
would. For what it's worth, I would not submit that one as a reliable
observation.

Haven't I heard somewhere that perception is reality or something to that
effect? I would say that if you think you've seen something that by its
nature is elusive in even a somewhat larger instrument then that is a
positive sighting. . .at least for the observer involved.


--
Martin

Martin R. Howell wrote:
Haven't I heard somewhere that perception is reality or something to that
effect? I would say that if you think you've seen something that by its
nature is elusive in even a somewhat larger instrument then that is a
positive sighting. . .at least for the observer involved.

Do you believe everything you've heard?

More seriously, I'm not sure what you mean by "positive," and I'm also
not sure whether you're supporting my observation or casting doubt on it,
but I myself would not consider what I saw a reliable observation. In
other words, there is a significant chance that I was mistaken. (I'm
sure at the time I didn't think so, but in retrospect, there has to be
that chance.)

The reason I *did* think I had seen it, however, was that my immediate
impression was, "Hey, something is wrong; I'm seeing the wrong thing,
because the spiral is going the wrong way." Only just afterward did it
occur to me that I was observing through an SCT with a star diagonal,
and in such an arrangement, the spiral *should* go "the wrong way."

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

"Brian Tung" wrote in message
...
Martin R. Howell wrote:
Haven't I heard somewhere that perception is reality or something to
that
effect? I would say that if you think you've seen something that by its
nature is elusive in even a somewhat larger instrument then that is a
positive sighting. . .at least for the observer involved.

Do you believe everything you've heard?

More seriously, I'm not sure what you mean by "positive," and I'm also
not sure whether you're supporting my observation or casting doubt on it,
but I myself would not consider what I saw a reliable observation. In
other words, there is a significant chance that I was mistaken. (I'm
sure at the time I didn't think so, but in retrospect, there has to be
that chance.)

The reason I *did* think I had seen it, however, was that my immediate
impression was, "Hey, something is wrong; I'm seeing the wrong thing,
because the spiral is going the wrong way." Only just afterward did it
occur to me that I was observing through an SCT with a star diagonal,
and in such an arrangement, the spiral *should* go "the wrong way."


I certainly was not casting doubt on your observation. . .I was affirming
that to you it may have been undifferentiable from an undeniable sighting
when using such a small scope -- insofar as to what detail is revealed to
the YOUR eye.

But. . .what is satisfying for one is not necessarily satisfying for all.
Believe me, I found this out the hard way when I submitted an observation
report to s.a.a. which included some nebula in which I claimed to have seen
a rather straight and pronounced edge. This was maybe 18 months or so ago.
I think it was Tom Trusock who replied that he could not see what I was
referring to. (I know, a preposition is a hell of a thing to end a sentence
WITH). ;o) I checked the image of it on LEDAS and the "straight edge"
was not there either, yet, at the time, I was so sure of what my eyes saw
and brain perceived that I would have bet a hundred bucks that the straight
edge was real. I'll have to take another look at it if I can locate its NGC
number in my log.

As for M51, with my 12.5 inch dob and a 6th magnitude location, the best I
can do on the arms is to get a core surrounded by a halo which appears to be
*slightly* more congested in a pattern of regularity which suggests an armed
structure.

--
Martin