earthshine: comparison between morning and evening.

For a long time I've noticed that you seem to get a brighter display of
earthshine in the moring ('New Moon in the Old Moon's arms') than in
the evening ('Old Moon in the New Moon's arms').

I wonder why this is? There must be more cloud reflecting the light
back to the Moon - but if so, why should there be more cloud on an
entire hemisphere of the Earth in the morning than in the evening?

brian wrote:
For a long time I've noticed that you seem to get a brighter display of
earthshine in the moring ('New Moon in the Old Moon's arms') than in
the evening ('Old Moon in the New Moon's arms').

I can't say I've noticed that before - but I will look out for it
now...

Could it be that your eyes are better adapted for morning displays than
for evening ones? That is, morning observations start with a dark sky
that's lightening (you're dark adapted to start with) while evening
sessions start with a light sky that's darkening (you start out poorly
dark adapted instead).

Cheers
Beats

justbeats wrote:
brian wrote:
For a long time I've noticed that you seem to get a brighter display of
earthshine in the moring ('New Moon in the Old Moon's arms') than in
the evening ('Old Moon in the New Moon's arms').

I can't say I've noticed that before - but I will look out for it
now...

Could it be that your eyes are better adapted for morning displays than
for evening ones? That is, morning observations start with a dark sky
that's lightening (you're dark adapted to start with) while evening
sessions start with a light sky that's darkening (you start out poorly
dark adapted instead).

Cheers
Beats

The Earth rotates into and out of its orbital shadow,recognition of
that orbital shadow which splits the globe in two would be something
that is productive in getting astronomy to mesh with the Earth sciences
of climatology and geology rather than the technically neutral night
falling or the sky brightening.

Fine for astrophotographers but lethal for the working principles for
the astronomical influences which condition global climate norms.

oriel36 wrote:
The Earth rotates into and out of its orbital shadow...[and a load of other stuff]

Doh! Of course! Please scratch my last proposition...

The amount of earthshine depends on the phase of the earth as viewed
from the moon (among other things - including weather).

So maybe the variation co-incidentally matched morning and evening for
you Brian...

"brian" wrote in message
ups.com...
For a long time I've noticed that you seem to get a brighter display of
earthshine in the moring ('New Moon in the Old Moon's arms') than in
the evening ('Old Moon in the New Moon's arms').

I wonder why this is? There must be more cloud reflecting the light
back to the Moon - but if so, why should there be more cloud on an
entire hemisphere of the Earth in the morning than in the evening?


Is this difference in brightness generally true or true only for western
Europe, for example?

As seen from the UK, in the evening, the sunlight is reflecting from the
Atlantic, the Americas, and the East Pacific. In the morning, the light is
reflected mainly from the Eurasian and African landmasses. On the whole,
land tends to be brighter than water (viz. photographs of Earth from space).

Incidentally, the determination of the Earth's albedo is done by studying
exactly this effect, and the measurements are difficult to make with
certainty.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

Originally Posted by brian

For a long time I've noticed that you seem to get a brighter display of
earthshine in the moring ('New Moon in the Old Moon's arms') than in
the evening ('Old Moon in the New Moon's arms').

I wonder why this is? There must be more cloud reflecting the light
back to the Moon - but if so, why should there be more cloud on an
entire hemisphere of the Earth in the morning than in the evening?

An interesting question. I've also noticed this and suspect the air is clearer and cleaner in the calm predawn sky compared to dusk coupled with the dark adapted eye after rising from sleep. The 3AM morning NLC displays this summer seem much more brilliant than the evening displays;-)

Nytecam

The title of Doctor has to be fraudulent insofar as a clinical approach
to astronomical phenomena reveals a cancer based on creating concepts
that do not recognise axial and orbital motions in isolation.You choose
a dumb concept of homogenised axial and orbital motion justified using
the calendar system.

Like the rest of your colleagues,who appear not to be capable of
helping themselves,the basic principle for axial rotation in isolation
is 24 hours/360 degrees while it is crucial to recognise orbital motion
in isolation for the working principles for Copernican heliocentricity
and its later refinements.

Your doctorates are presently not worth the paper they are written on.


Dr John Stockton wrote:
JRS: In article .com
, dated Mon, 24 Jul 2006 15:23:30 remote, seen in news:uk.sci.astronomy,
justbeats posted :

oriel36 wrote:
The Earth rotates into and out of its orbital shadow...[and a load of other
stuff]

Doh! Of course! Please scratch my last proposition...

Sarcasm is wasted on oriel36; I find a kill-rule more effective.

The amount of earthshine depends on the phase of the earth as viewed
from the moon (among other things - including weather).

Earthshine can only be seen when the Moon, as seen from the Earth. is
near (before/after) New; and at such times the Earth, as seen from the
Moon, is necessarily near Full.

If the Moon, as seen from Earth, is not (more or less) within its first
or last Eighths, then there will be too much light from the Sun-lit part
of the Moon for the Earth-lit part of the Moon to be visible (unaided
eye assumed); during that New Quarter, the Sun-lit proportion of the
Earth's disc, as seen from the Moon, does not much vary.

If the Moon is seen in AM/PM, then it is the dawn/dusk terminator that
can be seen from the Moon.

I'd attribute the effect, if any, to one or more of :-
Different AM/PM eye adaptation (unlikely; eye adapts too fast?);
Other AM/PM differences in the observer (sobriety, sleepiness, ...?);
Different AM/PM atmosphere clarity at the observer's location;
Different average atmospheric conditions near the AM/PM terminator, as
seen from the Moon, affecting Earth's mean effective albedo;
Something else.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.