Ultra Dark-Adaptation?

Last night I made observations of deep sky objects using hand-held,
20x80 binoculars. My limiting magnitude was 6.5 or better (same as on
a typical 'good' night). A look at M31 and M45 was enough to convince
me that this would be a good night to try for the California Nebula.

So I stood on my porch, leaned my head against the side of the house
for stabilizing purposes, pointed the binoculars toward the California
Nebula and: Bingo! There it was! Seriously, without a filter, the
California Nebula was instantly visible and absolutely unmistakable in
the 20x80 binoculars. I listed it in my notes as "easy" to see --
because it was!

So why was it easy? This is a bit of a mystery to me; but nearly
everything I looked at was "easy" on that night. Could it be possible
that my seeing the almost impossible on that night was a side effect
from staring into a bright, daytime sky near the Sun a couple of days
previously? Might a bit of 'extra' UV radiation to the eyes 36 hours
earlier caused my eyes to become (temporarily) more sensitive to
H-Beta (and perhaps other) radiation? This is a possibility that I am
currently considering. I vaguely recall a similar occurrence, and
similar speculation several years ago.

So, speculation (or facts) anyone? I'm somewhat hesitant to
repeatedly expose my eyes to UV rays 36 hours prior to deep sky
observing in an effort to collect experimental data. I *do* value my
eyesight!

PS: After checking a chart (just now), I looks like I saw Barnard's
Loop on the same night -- without even looking for it! I recall
noticing the Milky Way running beside Orion. Then there was a gap
followed by a narrower arc of "Milky Way" closer to Orion -- or so I
passed it off at the time. I did briefly consider the possibility
that I was seeing Barnard's Loop; but I was so preoccupied (at the
time) with my binocular observations that I didn't bother to take the
time to properly check it out. After all, some years ago I had tried
to see Barnard's Loop with the unaided eye -- without success.

PPS: At one point about a half dozen stealth aircraft (most likely
explanation -- all things considered) passed by. All were going in
the same direction; and all were widely separated from one another.
Air traffic is usually all but non-existent in my sky. It was quite
a night!
--
Bill
Celestial Journeys
http://cejour.blogspot.com

On Wed, 17 Jan 2007 22:03:06 -0700, W. H. Greer
wrote:

Last night I made observations of deep sky objects using hand-held,
20x80 binoculars. My limiting magnitude was 6.5 or better (same as on
a typical 'good' night). A look at M31 and M45 was enough to convince
me that this would be a good night to try for the California Nebula.

So I stood on my porch, leaned my head against the side of the house
for stabilizing purposes, pointed the binoculars toward the California
Nebula and: Bingo! There it was! Seriously, without a filter, the
California Nebula was instantly visible and absolutely unmistakable in
the 20x80 binoculars. I listed it in my notes as "easy" to see --
because it was!

So why was it easy? This is a bit of a mystery to me; but nearly
everything I looked at was "easy" on that night. Could it be possible
that my seeing the almost impossible on that night was a side effect
from staring into a bright, daytime sky near the Sun a couple of days
previously? Might a bit of 'extra' UV radiation to the eyes 36 hours
earlier caused my eyes to become (temporarily) more sensitive to
H-Beta (and perhaps other) radiation? This is a possibility that I am
currently considering. I vaguely recall a similar occurrence, and
similar speculation several years ago.

So, speculation (or facts) anyone? I'm somewhat hesitant to
repeatedly expose my eyes to UV rays 36 hours prior to deep sky
observing in an effort to collect experimental data. I *do* value my
eyesight!

Hi Bill-

It is very well established that extended exposure to bright light
reduces the depth of night vision that can be reached for up to 48
hours. Pilots and others on night missions take care to utilize very
dark glasses or stay inside for at least a day before. In your case, I'd
guess your enhanced sensitivity has some other explanation- somewhat
higher blood oxygen, extra rhodopsin from a dietary change, or some
other simple physiological cause.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
So why was it easy? This is a bit of a mystery to me; but nearly
everything I looked at was "easy" on that night.

Why assume it was your eyes? I've seen rare nights where the
transparency was simply jaw dropping. When that happens the contrast is
much enhanced, for everything from nebulae to the Milky Way. Did a
storm front happen to pass through lately? :-)

Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply take out your eye

Why assume it was your eyes? I've seen rare nights where the transparency
was simply jaw dropping. When that happens the contrast is much enhanced,
for everything from nebulae to the Milky Way. Did a storm front happen to
pass through lately? :-)

My sons and I have experienced just such nights a few times, and they are
truly marvelous. They make for great stories/remembrances, and someday I
hope that we will be able to visit someplace where this kind of observing is
the norm!

Dennis

Hi Dennis,

Dennis Woos wrote:
Why assume it was your eyes? I've seen rare nights where the transparency
was simply jaw dropping. When that happens the contrast is much enhanced,
for everything from nebulae to the Milky Way. Did a storm front happen to
pass through lately? :-)

My sons and I have experienced just such nights a few times, and they are
truly marvelous. They make for great stories/remembrances, and someday I
hope that we will be able to visit someplace where this kind of observing is
the norm!

I'm fortunate to live in one of those places, but even then we get one
night every year or two that makes the others seem rather unremarkable.
Those are the nights I'll never forget as well. I had a view of the
summer Milky Way a few years back that literally took my breath away!

Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply take out your eye

Greg Crinklaw wrote:

Why assume it was your eyes? I've seen rare nights where the
transparency was simply jaw dropping. When that happens the contrast is
much enhanced, for everything from nebulae to the Milky Way. Did a
storm front happen to pass through lately? :-)

Hi Greg, There wasn't really a storm front, just a clearing of the
sky. OTOH, it snowed in the past few hours and tonight might be clear
;-)

I've gotten into the habit of checking my NELM on a regular basis. I
can usually make out, often with some difficulty, a 6.4 magnitude star
near Polaris. Taking into account extinction with altitude, this
translates into a NELM of 6.5. There have been nights were I could
see 6.4 magnitude stars in Ursa Minor with greater ease; but the
night in question wasn't one of those nights! As for NELM, that night
was no better than my average. Yet, for faint fuzzies the night was
exceptional.

All things considered, I strongly suspect a physiological explanation.
The only clear suspect I can think of is my brief exposure to bright
sunlit sky a day and a half earlier.

OTOH, on different nights I do different observing projects. I don't
always look at the same objects. *Maybe* it was just the sky
conditions . . . but, but, there was also an aurora visible on that
night! Auroras do *not* improve the visibility of faint fuzzies. They
make the sky brighter!
--
Bill
Celestial Journeys
http://cejour.blogspot.com

Chris L Peterson wrote:

It is very well established that extended exposure to bright light
reduces the depth of night vision that can be reached for up to 48
hours. Pilots and others on night missions take care to utilize very
dark glasses or stay inside for at least a day before. In your case, I'd
guess your enhanced sensitivity has some other explanation- somewhat
higher blood oxygen, extra rhodopsin from a dietary change, or some
other simple physiological cause.

Hi Chris, I considered a dietary cause; but could think of nothing I
had consumed out of the ordinary. I'll try to keep a dietary diary --
just in case. Besides, it could prove helpful in the event of less
beneficial physiological changes.

I'm still a bit suspicious of exposure to bright light. In my case
the exposure was of short duration -- just a few minutes of actual
looking at the sky (with binoculars) in the vicinity of a blocked Sun.
I was indoors the rest of the time. So it was not "extended" exposure
to bright light. Plus there was the 36 hour delay prior to the night
session.

Over a period of several years, this is the *second* time that I've
had an abnormally good night after a relatively brief exposure to
brighter than normal sunlight.
--
Bill
Celestial Journeys
http://cejour.blogspot.com

On Thu, 18 Jan 2007 09:33:04 -0700, W. H. Greer
wrote:

I'm still a bit suspicious of exposure to bright light. In my case
the exposure was of short duration -- just a few minutes of actual
looking at the sky (with binoculars) in the vicinity of a blocked Sun.
I was indoors the rest of the time. So it was not "extended" exposure
to bright light. Plus there was the 36 hour delay prior to the night
session.

Over a period of several years, this is the *second* time that I've
had an abnormally good night after a relatively brief exposure to
brighter than normal sunlight.

I don't know of any mechanism that could explain enhanced scotopic
vision following any kind of exposure to bright light. But there are
many things about vision that are not yet fully understood. I guess I'd
suggest some careful experimentation- keeping in mind that the human
mind is very good at finding correlations even where none exist.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Greg Crinklaw wrote:

Why assume it was your eyes? I've seen rare nights where the
transparency was simply jaw dropping. When that happens the contrast is
much enhanced, for everything from nebulae to the Milky Way.

I've seen too many experienced observers report that to dismiss the
phenomenon as
unreal, but I can't imagine any physical explanation for it. I've never
seen a really good
explanation of what suboptimal transparency consists of -- I suspect
that there are,
in fact, numerous different factors at play. But at some level, it
seems to me that
it has to be related to extinction, a value that's routinely measured
by professional
astronomers. Rayleigh scattering places an absolute lower limit on
extinction, and
at good sites, the actual value's frequently not far off that absolute
limit. At best, the
difference between a pretty-decent night at a location like mine, in
the Eastern U.S.,
and the theoretical limit is a matter of something like 10% at the
zenith. And it's
hard to see how a 10% increase in light could yield the kind of
qualitative change
that you're describing.

- Tony Flanders

On Wed, 17 Jan 2007 22:03:06 -0700, W. H. Greer
wrote:

Last night I made observations of deep sky objects using hand-held,
20x80 binoculars. My limiting magnitude was 6.5 or better (same as on
a typical 'good' night). A look at M31 and M45 was enough to convince
me that this would be a good night to try for the California Nebula.

So I stood on my porch, leaned my head against the side of the house
for stabilizing purposes, pointed the binoculars toward the California
Nebula and: Bingo! There it was! Seriously, without a filter, the
California Nebula was instantly visible and absolutely unmistakable in
the 20x80 binoculars. I listed it in my notes as "easy" to see --
because it was!

So why was it easy? This is a bit of a mystery to me; but nearly
everything I looked at was "easy" on that night. Could it be possible
that my seeing the almost impossible on that night was a side effect
from staring into a bright, daytime sky near the Sun a couple of days
previously? Might a bit of 'extra' UV radiation to the eyes 36 hours
earlier caused my eyes to become (temporarily) more sensitive to
H-Beta (and perhaps other) radiation? This is a possibility that I am
currently considering. I vaguely recall a similar occurrence, and
similar speculation several years ago.

So, speculation (or facts) anyone? I'm somewhat hesitant to
repeatedly expose my eyes to UV rays 36 hours prior to deep sky
observing in an effort to collect experimental data. I *do* value my
eyesight!

I tend to fall on the side of arguing against this supposition. I
agree with Greg -- despite Tony Flanders' doubt -- that there are
nights with incredible atmospheric stillness and clarity, above and
beyond the norm. I don't know how often Tony gets to work in western
US high altitude skies, but out here, approximately once every couple
of months (I am averaging about six observing sessions every thirty
days at present) there is a really great night; and maybe once or
twice a YEAR there is one that is just bewilderingly perfect,
transcending all the rest. Why? I don't worry about the mechanism; I
just enjoy it!

Even if there is a little light pollution, on those nights that
combine atmospheric steadiness with excellent transparency, very faint
objects can be seen. I cannot see Barnard's Loop unless, however,
there is NO light pollution AND near perfect transparency. Ditto the
Witch's Head. The Horsehead is a little more forgiving; I've seen it
with naked eye limiting magnitude around 5.5; but the transparency has
to be splendid!

The last time I really studied Leo 1 was back in 1997; and that very
day, I had spent some hours outside in the brilliant sun (wearing
sunglasses, of course) doing window-washing. Yet, many hours later I
was able to see Leo 1 with my 8 inch scope, just a few miles south of
San Jose: another incredible night with near perfect seeing, though
there was no ground fog to cut off residual light from Morgan Hill,
Gilroy, and San Jose. On other occasions, with more "ordinary" air, I
have had less luck with this faint galaxy. One very probable reason
is that light scatter in the atmosphere, around Regulus, washed out
the galaxy.

But I do not think that I specifically saw Leo 1 *because* of the
bright sunlight I had been exposed to that day; in fact, my suspicion
is that I was working at a disadvantage. I believe that Herschel
tended to avoid light for a day or so before making some of his
confirmatory observations with the large speculum at Slough, staying
indoors and even resting his eyes as much as possible. It seems to me
that somebody as intellectually curious and experimentally bold as
Herschel would have tried EVERYTHING possible to give himself the best
opportunity of seeing the faintest objects. He certainly did not
intentionally expose himself to bright light; just the opposite!

Finally, Bill: your website of drawings, and your blog, are both very
interesting and valuable. I've just added them to the short list of
links on my own site, which includes only a *few* very distinctive
amateur astronomical websites that I have been impressed by.

AstroApp