Just a brief answer... glad to be on the list!

-----Original Message-----
Subject: RE: [AstronomyWeather] Re: Ground effect on "seeing"

>It is a pleasure to see you joining  the group Alister.  Regarding cases
you
>mention with upper ridge sitting over alberta,
>how bad was the seeing when the jetstream (or mdt-svr turbulence area)
moved
>overhead... on a scale of 5?

Oh, it went from 4 (very good) to 1 or 0 (horrible).

>Was the jetstream blowing at 90 degrees from the rockies on those
occasions?

The occasions I'm referring to were where the jet stream was from northwest
to southeast. On those occasions when it is SW chinook over the Rockies, I
never have any expectations of good seeing, and it usually is poor to
mediocre, and from what I've heard from Alan Dyer, it's usually quite
horrible from Calgary. I don't think I've ever heard of good seeing in a SW
flow.

Alister.

Well, according to the book I usually reference these things from:
Descriptive Micrometeorology, by R.E. Munn, Advanced in Geophysics,
supplement 1, 1966.  LCCCN 65-26406, Academic Press,  111 Fifth Ave.,
New York 10003 -- and every scientific paper I've read or written
that deals with meteorology  (mostly about Mars) the boundary layer
is 12 meters above the surface.  I have never heard the boundary
layer is 3000' and below.

DustyMars
--- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
wrote:
> In the world of meteorology, the boundary layer is usually below
3000 feet
> (1000 meters). It is the layer where
> the airmass creates an inversion during the night... it is also
called the
> mixing layer.
>
> Allan
>
>  -----Message d'origine-----
> De : jdb_mars [mailto:jdb_mars@y...]
> Envoye : 30 aout, 2002 06:30
> A : AstronomyWeather@y...
> Objet : [AstronomyWeather] Re: Ground effect on "seeing"
>
>
>   Actually the boundary layer is the last 12 meters to the
surface.  At
>   least it was the last time I studied micrometeorology.
>
>   DustyMars
>
>   --- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
>   wrote:
>   > Attilla is a good student,
>   >
>   > Indeed, the corrolations is higher with low level wind than the
>   tropopause.
>   > It doesn't mean the tropopause doesn't create seeing, but it
tells
>   me the
>   > boundary layer (first 3000 feet) is the most important factor to
>   the seeing
>   > by a factor of two as opposed to the jetstream level. I do
calculate
>   > windshear at high and low levels and I weighted the equations
>   accordingly to
>   > my study with heights. I also look at topography lenght in one
of
>   the
>   > equation I use to simulate the downstream mountain effects.
>   > This summer, I added another part in the program to give more
>   weight when a
>   > low level jetstream is overhead which should reduce seeing ore
than
>   it was
>   > forecasting. This was an ajustement I did because I didn't like
the
>   forecast
>   > over southern U.S. in some specific occasions. In fact I didn't
have
>   > feedback... it was a guess!
>   >
>   > Allan
>   >
>   >
>   >   -----Message d'origine-----
>   >   De : attilladanko [mailto:danko@c...]
>   >   Envoye : 28 aout, 2002 18:03
>   >   A : AstronomyWeather@y...
>   >   Objet : [AstronomyWeather] Re: Ground effect on "seeing"
>   >
>   >
>   >   --- In AstronomyWeather@y..., "Bruce L. Gary"
<brucelgary@c...>
>   >   wrote: >
>   >   > If this is true, then Allan Rahill's calculations at the
CMC,
>   based
>   >   as they
>   >   > are on synoptic scale data, might be "capturing" only the
>   >   tropopause
>   >   > component
>   >
>   >   I hope Allan replies in detail.
>   >
>   >   But I know a little of how he does it. His own data, 541
>   >   observations of seeing from Dorval Quebec, showed that low
>   >   altitude winds had the greatest correlation on telescopic
seeing.
>   >   (He also saw a correleation to the jet steam,
>   >   but it was smaller.) So he uses temperature gradients and
>   >   wind-induced turbulence data, but he weights it giving much
>   >   weight to low altitude effects.
>   >
>   >   -ad
>   >
>   >
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>   >
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>   >
>   >
>   >   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
>   Service.
>   >
>   >
>   >
>   > [Non-text portions of this message have been removed]
>
>
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>
> [Non-text portions of this message have been removed]

No, unless you live nearby Chicago or other major airports where airplane
turns around before landing.
When there is a lot of moisture at the tropopause, in some rare occasions I
have seen a lot of contrails on GOES images
nearby these airports. They produce thin clouds and can affect sky
transparency. It may also have a
small impact on local seeing since thin cirrus produced from these jets
reduce the cooling trend during the night.
But, most of our observing sites are far from these airports and I would
guess the impact is quite small.

[Allan Rahill]

  -----Message d'origine-----
De : Bemusabord@... [mailto:Bemusabord@...]
Envoye : 30 aout, 2002 08:45
A : AstronomyWeather@yahoogroups.com
Objet : [AstronomyWeather] Seeing, transparency and air traffic


   We were at the Black Forest Star Party (Cherry Springs State Park, PA.) in
   the wake of 9/11 (it was held just a few days later, when there were no
   planes flying except military) which normally is heavily overflown by air
   traffic.  We noted that both the seeing and transparancy were much better
   than usual.

   Does heavy air traffic have an effect on these factors and if so, would it
   make sense that in addition to dark skies, it is probably advisable to
avoid
   being under a major air traffic route also?

   Thom Bemus

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[Non-text portions of this message have been removed]

In the world of meteorology, the boundary layer is usually below 3000 feet
(1000 meters). It is the layer where
the airmass creates an inversion during the night... it is also called the
mixing layer.

Allan

  -----Message d'origine-----
De : jdb_mars [mailto:jdb_mars@...]
Envoye : 30 aout, 2002 06:30
A : AstronomyWeather@yahoogroups.com
Objet : [AstronomyWeather] Re: Ground effect on "seeing"


   Actually the boundary layer is the last 12 meters to the surface.  At
   least it was the last time I studied micrometeorology.

   DustyMars

   --- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
   wrote:
   > Attilla is a good student,
   >
   > Indeed, the corrolations is higher with low level wind than the
   tropopause.
   > It doesn't mean the tropopause doesn't create seeing, but it tells
   me the
   > boundary layer (first 3000 feet) is the most important factor to
   the seeing
   > by a factor of two as opposed to the jetstream level. I do calculate
   > windshear at high and low levels and I weighted the equations
   accordingly to
   > my study with heights. I also look at topography lenght in one of
   the
   > equation I use to simulate the downstream mountain effects.
   > This summer, I added another part in the program to give more
   weight when a
   > low level jetstream is overhead which should reduce seeing ore than
   it was
   > forecasting. This was an ajustement I did because I didn't like the
   forecast
   > over southern U.S. in some specific occasions. In fact I didn't have
   > feedback... it was a guess!
   >
   > Allan
   >
   >
   >   -----Message d'origine-----
   >   De : attilladanko [mailto:danko@c...]
   >   Envoye : 28 aout, 2002 18:03
   >   A : AstronomyWeather@y...
   >   Objet : [AstronomyWeather] Re: Ground effect on "seeing"
   >
   >
   >   --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
   >   wrote: >
   >   > If this is true, then Allan Rahill's calculations at the CMC,
   based
   >   as they
   >   > are on synoptic scale data, might be "capturing" only the
   >   tropopause
   >   > component
   >
   >   I hope Allan replies in detail.
   >
   >   But I know a little of how he does it. His own data, 541
   >   observations of seeing from Dorval Quebec, showed that low
   >   altitude winds had the greatest correlation on telescopic seeing.
   >   (He also saw a correleation to the jet steam,
   >   but it was smaller.) So he uses temperature gradients and
   >   wind-induced turbulence data, but he weights it giving much
   >   weight to low altitude effects.
   >
   >   -ad
   >
   >
   >         Yahoo! Groups Sponsor
   >               ADVERTISEMENT
   >
   >
   >
   >   To unsubscribe from this group, send an email to:
   >   AstronomyWeather-unsubscribe@y...
   >
   >
   >
   >   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
   Service.
   >
   >
   >
   > [Non-text portions of this message have been removed]


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[Non-text portions of this message have been removed]

I can speak only from the limited perspective of an Arizona observer.
I'd say that aircraft contrails have no significant effect on sky
conditions, at least on nights that you'd want to be observing.  Long
and persistent contrails are a sure sign that there's plenty of water
vapor in the upper levels of the atmosphere, and probably some cirrus
clouds.  If the conditions are dry enough for observing, contrails
shouldn't be any longer than a few degrees.

Now aesthetically, I think anybody would much rather be under a
plane-less sky (not for the reason of a year ago, of course).  Anwhere
north of about Tucson in Arizona is under the influence of major
east-west air traffic heading to and from California coastal cities.
As always, blame it on California.

Tom


--- In AstronomyWeather@y..., Bemusabord@a... wrote:
>
> Does heavy air traffic have an effect on these factors and if so,
would it
> make sense that in addition to dark skies, it is probably advisable
to avoid
> being under a major air traffic route also?

Some good stories (articles) on "astronomical seeing" can be found at:

http://www.cmc.ec.gc.ca/cmc/htmls/seeing_e.html

"How to Predict Seeing," By Eric J. Douglass, S&T, Observer's Log -
January 2000, p. 125-130

http://groups.yahoo.com/group/Mars-ALPO/files/misc/SeeingSF.htm

DustyMars


--- In AstronomyWeather@y..., "jdb_mars" <jdb_mars@y...> wrote:
> Actually the boundary layer is the last 12 meters to the surface.
At
> least it was the last time I studied micrometeorology.
>
> DustyMars
>
> --- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
> wrote:
> > Attilla is a good student,
> >
> > Indeed, the corrolations is higher with low level wind than the
> tropopause.
> > It doesn't mean the tropopause doesn't create seeing, but it
tells
> me the
> > boundary layer (first 3000 feet) is the most important factor to
> the seeing
> > by a factor of two as opposed to the jetstream level. I do
calculate
> > windshear at high and low levels and I weighted the equations
> accordingly to
> > my study with heights. I also look at topography lenght in one of
> the
> > equation I use to simulate the downstream mountain effects.
> > This summer, I added another part in the program to give more
> weight when a
> > low level jetstream is overhead which should reduce seeing ore
than
> it was
> > forecasting. This was an ajustement I did because I didn't like
the
> forecast
> > over southern U.S. in some specific occasions. In fact I didn't
have
> > feedback... it was a guess!
> >
> > Allan
> >
> >
> >   -----Message d'origine-----
> >   De : attilladanko [mailto:danko@c...]
> >   Envoye : 28 aout, 2002 18:03
> >   A : AstronomyWeather@y...
> >   Objet : [AstronomyWeather] Re: Ground effect on "seeing"
> >
> >
> >   --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
> >   wrote: >
> >   > If this is true, then Allan Rahill's calculations at the CMC,
> based
> >   as they
> >   > are on synoptic scale data, might be "capturing" only the
> >   tropopause
> >   > component
> >
> >   I hope Allan replies in detail.
> >
> >   But I know a little of how he does it. His own data, 541
> >   observations of seeing from Dorval Quebec, showed that low
> >   altitude winds had the greatest correlation on telescopic
seeing.
> >   (He also saw a correleation to the jet steam,
> >   but it was smaller.) So he uses temperature gradients and
> >   wind-induced turbulence data, but he weights it giving much
> >   weight to low altitude effects.
> >
> >   -ad
> >
> >
> >         Yahoo! Groups Sponsor
> >               ADVERTISEMENT
> >
> >
> >
> >   To unsubscribe from this group, send an email to:
> >   AstronomyWeather-unsubscribe@y...
> >
> >
> >
> >   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
> >
> >
> >
> > [Non-text portions of this message have been removed]

We were at the Black Forest Star Party (Cherry Springs State Park, PA.) in
the wake of 9/11 (it was held just a few days later, when there were no
planes flying except military) which normally is heavily overflown by air
traffic.  We noted that both the seeing and transparancy were much better
than usual.

Does heavy air traffic have an effect on these factors and if so, would it
make sense that in addition to dark skies, it is probably advisable to avoid
being under a major air traffic route also?

Thom Bemus

Actually the boundary layer is the last 12 meters to the surface.  At
least it was the last time I studied micrometeorology.

DustyMars

--- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
wrote:
> Attilla is a good student,
>
> Indeed, the corrolations is higher with low level wind than the
tropopause.
> It doesn't mean the tropopause doesn't create seeing, but it tells
me the
> boundary layer (first 3000 feet) is the most important factor to
the seeing
> by a factor of two as opposed to the jetstream level. I do calculate
> windshear at high and low levels and I weighted the equations
accordingly to
> my study with heights. I also look at topography lenght in one of
the
> equation I use to simulate the downstream mountain effects.
> This summer, I added another part in the program to give more
weight when a
> low level jetstream is overhead which should reduce seeing ore than
it was
> forecasting. This was an ajustement I did because I didn't like the
forecast
> over southern U.S. in some specific occasions. In fact I didn't have
> feedback... it was a guess!
>
> Allan
>
>
>   -----Message d'origine-----
>   De : attilladanko [mailto:danko@c...]
>   Envoye : 28 aout, 2002 18:03
>   A : AstronomyWeather@y...
>   Objet : [AstronomyWeather] Re: Ground effect on "seeing"
>
>
>   --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
>   wrote: >
>   > If this is true, then Allan Rahill's calculations at the CMC,
based
>   as they
>   > are on synoptic scale data, might be "capturing" only the
>   tropopause
>   > component
>
>   I hope Allan replies in detail.
>
>   But I know a little of how he does it. His own data, 541
>   observations of seeing from Dorval Quebec, showed that low
>   altitude winds had the greatest correlation on telescopic seeing.
>   (He also saw a correleation to the jet steam,
>   but it was smaller.) So he uses temperature gradients and
>   wind-induced turbulence data, but he weights it giving much
>   weight to low altitude effects.
>
>   -ad
>
>
>         Yahoo! Groups Sponsor
>               ADVERTISEMENT
>
>
>
>   To unsubscribe from this group, send an email to:
>   AstronomyWeather-unsubscribe@y...
>
>
>
>   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.
>
>
>
> [Non-text portions of this message have been removed]

It is a pleasure to see you joining  the group Alister.  Regarding cases you
mention with upper ridge sitting over alberta,
how bad was the seeing when the jetstream (or mdt-svr turbulence area) moved
overhead... on a scale of 5?
Was the jetstream blowing at 90 degrees from the rockies on those occasions?

Thanks

Allan


   -----Message d'origine-----
   De : Ling,Alister [Edm] [mailto:alister.ling@...]
   Envoye : 29 aout, 2002 11:35
   A : 'AstronomyWeather@yahoogroups.com'
   Objet : RE: [AstronomyWeather] Re: Ground effect on "seeing"


   It is very important NOT to neglect tropopause effects, as Allan
indicates.
   There have been several occasions in the past where I'm sitting in the
   middle of a big surface high in winter, good inversion very little wind in
   the lower 5,000 ft, and seeing was great until the jet broke across the
   upper ridge. I later checked the aviation turbulence panels and there was
a
   band of MDT-SVR going through.

   I'm not saying the lower levels aren't important - they obviously are,
just
   that one cannot reduce the importance the upper levels too much.

   Alister.

   -----Original Message-----
   From: Allan Rahill [mailto:allan.rahill@...]
   Sent: Wednesday, August 28, 2002 8:13 PM
   To: AstronomyWeather@yahoogroups.com
   Subject: RE: [AstronomyWeather] Re: Ground effect on "seeing"


   Attilla is a good student,

   Indeed, the corrolations is higher with low level wind than the
tropopause.
   It doesn't mean the tropopause doesn't create seeing, but it tells me the
   boundary layer (first 3000 feet) is the most important factor to the
seeing
   by a factor of two as opposed to the jetstream level. I do calculate
   windshear at high and low levels and I weighted the equations accordingly
to
   my study with heights. I also look at topography lenght in one of the
   equation I use to simulate the downstream mountain effects.
   This summer, I added another part in the program to give more weight when
a
   low level jetstream is overhead which should reduce seeing ore than it was
   forecasting. This was an ajustement I did because I didn't like the
forecast
   over southern U.S. in some specific occasions. In fact I didn't have
   feedback... it was a guess!

   Allan


     -----Message d'origine-----
     De : attilladanko [mailto:danko@...]
     Envoye : 28 aout, 2002 18:03
     A : AstronomyWeather@yahoogroups.com
     Objet : [AstronomyWeather] Re: Ground effect on "seeing"


     --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
     wrote: >
     > If this is true, then Allan Rahill's calculations at the CMC, based
     as they
     > are on synoptic scale data, might be "capturing" only the
     tropopause
     > component

     I hope Allan replies in detail.

     But I know a little of how he does it. His own data, 541
     observations of seeing from Dorval Quebec, showed that low
     altitude winds had the greatest correlation on telescopic seeing.
     (He also saw a correleation to the jet steam,
     but it was smaller.) So he uses temperature gradients and
     wind-induced turbulence data, but he weights it giving much
     weight to low altitude effects.

     -ad


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[Non-text portions of this message have been removed]

This is the way I always explained the effect of moisture to reduce
transparency, scattering.
Moisture also increase somewhat the extinction.
I have to add, many years ago, I was in the country observing and I noticed
the sky transparency becoming excellent and later on average on the same
night. When I arrived home I did look at water vapor images to find out a
narrow dark band moved overhead late in the evening and south of my
observation location during the night. I than consider to produce the
transparency forecast based on humidity only.

Of course aerosols are very important for those living mainly over southern
latitude. If youk look at aerosol detector images, it is a rare event for
most northern latitude regions to see dust, smoke or any other particules.
Smog remains the biggest problem for all industrial  cities.

Allan


  -----Message d'origine-----
De : attilladanko [mailto:danko@...]
Envoye : 29 aout, 2002 10:26
A : AstronomyWeather@yahoogroups.com
Objet : [AstronomyWeather] a FAQ question


   I'd like to put the answer to this on in a FAQ:

   Q: If water vapor is a clear colorless gas, why does
      the presence of water vapour, without droplets, reduce
      atmospheric transparency.

   I've always guessed that it has to do with scattering light by
   polar molecules.

   -ad


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[Non-text portions of this message have been removed]

It is very important NOT to neglect tropopause effects, as Allan indicates.
There have been several occasions in the past where I'm sitting in the
middle of a big surface high in winter, good inversion very little wind in
the lower 5,000 ft, and seeing was great until the jet broke across the
upper ridge. I later checked the aviation turbulence panels and there was a
band of MDT-SVR going through.

I'm not saying the lower levels aren't important - they obviously are, just
that one cannot reduce the importance the upper levels too much.

Alister.

-----Original Message-----
From: Allan Rahill [mailto:allan.rahill@...]
Sent: Wednesday, August 28, 2002 8:13 PM
To: AstronomyWeather@yahoogroups.com
Subject: RE: [AstronomyWeather] Re: Ground effect on "seeing"


Attilla is a good student,

Indeed, the corrolations is higher with low level wind than the tropopause.
It doesn't mean the tropopause doesn't create seeing, but it tells me the
boundary layer (first 3000 feet) is the most important factor to the seeing
by a factor of two as opposed to the jetstream level. I do calculate
windshear at high and low levels and I weighted the equations accordingly to
my study with heights. I also look at topography lenght in one of the
equation I use to simulate the downstream mountain effects.
This summer, I added another part in the program to give more weight when a
low level jetstream is overhead which should reduce seeing ore than it was
forecasting. This was an ajustement I did because I didn't like the forecast
over southern U.S. in some specific occasions. In fact I didn't have
feedback... it was a guess!

Allan


   -----Message d'origine-----
   De : attilladanko [mailto:danko@...]
   Envoye : 28 aout, 2002 18:03
   A : AstronomyWeather@yahoogroups.com
   Objet : [AstronomyWeather] Re: Ground effect on "seeing"


   --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
   wrote: >
   > If this is true, then Allan Rahill's calculations at the CMC, based
   as they
   > are on synoptic scale data, might be "capturing" only the
   tropopause
   > component

   I hope Allan replies in detail.

   But I know a little of how he does it. His own data, 541
   observations of seeing from Dorval Quebec, showed that low
   altitude winds had the greatest correlation on telescopic seeing.
   (He also saw a correleation to the jet steam,
   but it was smaller.) So he uses temperature gradients and
   wind-induced turbulence data, but he weights it giving much
   weight to low altitude effects.

   -ad


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               ADVERTISEMENT



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I'd like to put the answer to this on in a FAQ:

Q: If water vapor is a clear colorless gas, why does
    the presence of water vapour, without droplets, reduce
    atmospheric transparency.

I've always guessed that it has to do with scattering light by
polar molecules.

-ad

Thanks Your charts pretty much confirm what I thought: I live in a cloudy spot
I think it's very odd that sunshine/cloudyness data isnt more common on the web.

Btw, its my fault that your attachment got stripped. I set this email list to
decline
attachements as a method of preventing the spread of viruses. Instead of sending
attachments, I suggest people post their attachment to the files section of the
group: http://groups.yahoo.com/group/AstronomyWeather/files/
and then include a link in their email.

However, if most members want attachments turned on, I will do that.

-ad


----- Original Message -----
From: Bruce L. Gary <brucelgary@...>
To: <AstronomyWeather@yahoogroups.com>
Sent: Wednesday, August 28, 2002 11:50 PM
Subject: [AstronomyWeather] Sunshine map web page


> Here's a link to a "sunshine map" of the United States (that I just
> created, since my attachment on a previous posting got stripped).  Sorry
> Canada isn't included.
>
> http://reductionism.net.seanic.net/sunshinemap.html
>
> Bruce L. Gary
> Santa Barbara, CA

Here's a link to a "sunshine map" of the United States (that I just
created, since my attachment on a previous posting got stripped).  Sorry
Canada isn't included.

http://reductionism.net.seanic.net/sunshinemap.html

Bruce L. Gary
Santa Barbara, CA

[Non-text portions of this message have been removed]

I have a "sunshine map" from an old geography book (that my daughter used
as a coloring book), and I'll attach a copy of it here.  I don't know if
image attachments get included in the post, but if it doesn't anyone can
e-mail me directly and ask for it.  I had to save it with JPEG 10% quality
for this attachment to keep file size small (72 KB).  I could attach better
versions for anyone with wide bandwidth.

Yuma, AZ is the winner, which agrees with the Excel spreadsheet tabulation.

At 08:02 PM 08/28/2002, you wrote:
>I sometimes get asked for long term cloud cover
>stats, like the number of clear hours per month,
>for some specific latitude and longitude.
>(Seems like real-esate questions to me.)
>
>I've never found anything like that on the web.
>
>There is a list of mean number of cloud free
>days for US cities. I've posted it to the
>files section:
><http://groups.yahoo.com/group/AstronomyWeather/files/>http://groups.yahoo.com/\
group/AstronomyWeather/files/
>
>I even encouraged one questioner to write Fred Espenak
>because Fred's eclipse write-ups discuss optimal
>eclipse observing locations based on average cloudyness
>for locations and dates. However, Fred replied that the
>database was private and not available on the net.
>
>Anyone have better resources for average cloudyness
>on the web?
>
>-ad

Bruce L. Gary
Santa Barbara, CA

[Non-text portions of this message have been removed]

I sometimes get asked for long term cloud cover
stats, like the number of clear hours per month,
for some specific latitude and longitude.
(Seems like real-esate questions to me.)

I've never found anything like that on the web.

There is a list of mean number of cloud free
days for US cities. I've posted it to the
files section:
http://groups.yahoo.com/group/AstronomyWeather/files/

I even encouraged one questioner to write Fred Espenak
because Fred's eclipse write-ups discuss optimal
eclipse observing locations based on average cloudyness
for locations and dates. However, Fred replied that the
database was private and not available on the net.

Anyone have better resources for average cloudyness
on the web?

-ad

I've created a couple of folders for links.

I've added all of the astronomy-specific
weather sites that I know.
http://makeashorterlink.com/?Q56A353A1

Please feel free to add more.

-ad

Attilla is a good student,

Indeed, the corrolations is higher with low level wind than the tropopause.
It doesn't mean the tropopause doesn't create seeing, but it tells me the
boundary layer (first 3000 feet) is the most important factor to the seeing
by a factor of two as opposed to the jetstream level. I do calculate
windshear at high and low levels and I weighted the equations accordingly to
my study with heights. I also look at topography lenght in one of the
equation I use to simulate the downstream mountain effects.
This summer, I added another part in the program to give more weight when a
low level jetstream is overhead which should reduce seeing ore than it was
forecasting. This was an ajustement I did because I didn't like the forecast
over southern U.S. in some specific occasions. In fact I didn't have
feedback... it was a guess!

Allan


   -----Message d'origine-----
   De : attilladanko [mailto:danko@...]
   Envoye : 28 aout, 2002 18:03
   A : AstronomyWeather@yahoogroups.com
   Objet : [AstronomyWeather] Re: Ground effect on "seeing"


   --- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
   wrote: >
   > If this is true, then Allan Rahill's calculations at the CMC, based
   as they
   > are on synoptic scale data, might be "capturing" only the
   tropopause
   > component

   I hope Allan replies in detail.

   But I know a little of how he does it. His own data, 541
   observations of seeing from Dorval Quebec, showed that low
   altitude winds had the greatest correlation on telescopic seeing.
   (He also saw a correleation to the jet steam,
   but it was smaller.) So he uses temperature gradients and
   wind-induced turbulence data, but he weights it giving much
   weight to low altitude effects.

   -ad


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[Non-text portions of this message have been removed]

Shannon,

Yes the baloon soundings are used in the analysis.
When I started with my study, I had the same question than you regarding the
lifted and richardson number and I did compiled them. Since in northern
latitude, convective season is quite short, I didn't get too worried about
the lifted, but I can assure you there is corrolation with this index. For
Richardson number, well there is possibly a corrolation. I use Elrod
equations to calculate the seeing which gives you feedback on vortex and
vertical windshear.

I don't use Refractive Index Structure Constants in my calculation, but my
approach is somewhat similar and in the smae time different way to calculate
seeing.

Allan
   -----Message d'origine-----
   De : mann9471 [mailto:mannsj@...]
   Envoye : 28 aout, 2002 16:58
   A : AstronomyWeather@yahoogroups.com
   Objet : [AstronomyWeather] Seeing Forecasts with Atmospheric Soundings
etc,...


   Are the current seeing forecasts at clear sky clocks using sounding
   data from balloon radiosondes? I am just starting off into the world
   of "astronomic seeing" and am curious if lifted indices and bulk
   richardson numbers are of any use in guesstimating relative seeing
   rankings. Also, how would one even start to approximate Refractive
   Index Structure Constants with readily available data via the net, if
   at all possible?

   - thanks

   - Shannon Mann


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[Non-text portions of this message have been removed]

Thanks Bruce for your ''think out loud''. I always enjoy reading your
thoughts and these express my thoughts as well. I agree with most of the
item you mentioned. Your suggestion about the declination sound good, and I
thing we can add.. choose a star near the meridian.

Allan
   -----Message d'origine-----
   De : brucelgary [mailto:brucelgary@...]
   Envoye : 28 aout, 2002 12:47
   A : AstronomyWeather@yahoogroups.com
   Objet : [AstronomyWeather] Re: Seeing for CCD users versus visual
observers


   Attila and Allan,

   Thanks to both of you for excellent suggestions.  Turning off the
   sidereal drive and registering a star track on the CCD strikes me as a
   great idea with many possibilities.

   Allow me to "think out loud" with the following posting.  These
   thoughts are based on my other CCD work (precision photometry).

   Observing Procedure:

   1) The star used for FWHM analysis should not saturate the CCD.  For
   16-bit CCDs without anti-blooming the saturation begins at about
   40,000 counts (where maximum counts possible is 65,535).  Use only a
   star whose highest counts is lower than that.

   2) Do a very careful focus before the exposure.

   3) I don't think the CCD temperature setting will matter provided the
   cooler's duty cycle is below 90%, for example (so that the CCD
   temperature is stable).

   4) A standard declination should be used; otherwise the speed of the
   star's motion across the CCD will be different on different nights.
   Although it will be desireable to also be near zenith it is also
   important to have some flexibility on choosing drift speed to
   facilitate comparisons with other observers.  Maybe a preferred zenith
   angle should be chosen, such as 30 degrees.  With such a goal there's
   a circle centered on zenith with a 30 degree radius that spans a 60
   degree declination range - which affords a good range of drift rates.

   5) Different telescope/CCD configurations have different image scales
   ["arc/pixel].  This issue may deserve some thought if observations are
   to be compared.

   Analysis considerations:

   1) Track width, such as FWHM, cannot be measured with standard image
   analysis software (such as MaxIm DL).  The user will have to manually
   probe cross-sections to estimate width.

   2) Motion "along track" will cause photons to "pile up" and increase
   the counts, and also the opposite.  Thus, there is a means for
   extracting motion information in the orthogonal direction, which
   could either serve to validate the FWHM measurements or perhaps
   replace them (if they're easier to analyze).

   3) Analysis of tracks has the great feature that it allows for an
   estimate of temporal periodicities.  In other words, if the image
   wander is slow the track width and brightness will vary slowly along
   the track, etc.  A spectral analysis of temporal variations would even
   be possible for the advanced observer.

   4) Images are "objective" and could be uploaded to an archive for
   others to use.  Eventually someone may write a program to take a FITS
   image and automatically perform an analysis of seeing parameters.
   (That project might actually interest me!)

   5) Objective seeing information might possibly be of use to
   atmospheric scientists interested in "waves in the atmosphere" (I'm
   one such a person).  Predictions of seeing properties could be tested,
   being based on the wind altitude profile, topography, temperature and
   vapor density altitude profile, etc.

   I guess I'd have to say that the more I think about the possibilities
   of using CCDs for monitoring "atmospheric seeing" the more interested
   I'm becoming in  it!  Surely, some of the professionals have addressed
   this subject.  How do we gain from their experiences?  Before I start
   trying to contact them, let's hope somebody in this "group" can help
   make that connection.


   --- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
   wrote:
   > Hi Gary...
   >
   > Actually, I am trying to find the best way to corrolate the seeing
   forecast
   > to CCD applications. Lately, I did only 3 sessions of CCD to look at
   the
   > result when the seeing was particular good, ie about 4-5/5. What I
   found so
   > far, despite the diffraction pattern is clearly seen all the time,
   (which
   > also means if there was a visible planet, we would have seen high
   quality
   > details all the time), a long CCD exposure gave me stars with about
   2 arc
   > seconds with my C14. This was a disapointment because I expected a
   bit
   > smaller star diameter. Despite excellent visual seeing, the star
   dance
   > around it center, not much but enough to blur CCD image. I am just
   starting
   > and I will have to keep record of my observations. I hope to end up
   with a
   > conclusion in a few months.
   >
   > Last night, I  took a few CCD shots of magnitude 8-10 stars with
   sideral
   > motor turned off. We can see star trails with seeing wobble with
   time having
   > a wave form. We can mesure the average amplitude of this wave to
   measure CCD
   > seeing. There may be something we can do with this approach. I will
   > experiment.
   >
   > The biggest problem to measure seeing is to use the same star or
   star having
   > the same magnitude. We also have to use the same exposure, same
   cooling
   > temperature.
   >
   > Allan
   >   -----Message d'origine-----
   >   De : Bruce L. Gary [mailto:brucelgary@c...]
   >   Envoye : 28 aout, 2002 02:36
   >   A : AstronomyWeather@y...
   >   Objet : [AstronomyWeather] Seeing for CCD users versus visual
   observers
   >
   >
   >   As a CCD user I feel the need for a method of measuring
   "atmospheric
   >   seeing" that is specifically directed to what a CCD records after
   a
   >   well-guided long exposure.  On that rare occasion when I observe
   visually
   > I
   >   try to imagine what a CCD would record after a few seconds.  I am
   struck
   > by
   >   how important "image wander" must be, and how unimportant will be
   those
   >   brief moments of sharp clarity that visual observers wait for.
   >
   >   Can anyone tell me if a protocol has been developed for assessing
   "CD
   > seeing"?
   >
   >   Bruce "StarGeezer" Gary
   >   Santa Barbara, CA
   >
   >
   >         Yahoo! Groups Sponsor
   >               ADVERTISEMENT
   >
   >
   >
   >   To unsubscribe from this group, send an email to:
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   >
   >
   >
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   Service.


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[Non-text portions of this message have been removed]

>We can see star trails with seeing wobble with time having a wave form. We
can mesure the average amplitude of this wave to measure CCD >seeing.

   Isnt it more complicated that that? Peridoic error in the drive would
introduce a regular woble with a perioud of a minute or two.
   Atmosphereic refraction would introduce a drift, that is much slower.
   [Allan Rahill]

   In fact there was no tracking at all sine I turned off the drive. To my
big surprised, there was regular wave pattern from the atmosphere. I look
twice when ùI saw that. Since I was just experiemnting.I didn't save the
image. UI should have. It is cloudy tonight.


   I think it might be a lot simpler if we can say that an 14" aperture is
big enought that seeing will not cause the
   image to shift in positions, but to fuzz. In that case, we should be able
to estimage seeing from the thickness of
   a startrail, not the amplitude of the wavyness of the startrail.
   [Allan Rahill]

   You are close to the truth, the C14 offer most of the time images to fuzz
but when the seeing is good, I found out is fuzz again for two reasons.
   1- there is indeed shift in position despite airy disk cleanly visible
which add fuzz in CCD
   2- Poor optical quality of the C14 (rough optics) which diffuse a halo of
light around stars. It is far away to be clean as my 22 inch telescope.

   Allan

   just guessing.

   -ad

     ----- Original Message -----
     From: Allan Rahill
     To: AstronomyWeather@yahoogroups.com
     Sent: Wednesday, August 28, 2002 9:43 AM
     Subject: RE: [AstronomyWeather] Seeing for CCD users versus visual
observers


     Hi Gary...

     Actually, I am trying to find the best way to corrolate the seeing
forecast to CCD applications. Lately, I did only 3 sessions of CCD to look
at the result when the seeing was particular good, ie about 4-5/5. What I
found so far, despite the diffraction pattern is clearly seen all the time,
(which also means if there was a visible planet, we would have seen high
quality details all the time), a long CCD exposure gave me stars with about
2 arc seconds with my C14. This was a disapointment because I expected a bit
smaller star diameter. Despite excellent visual seeing, the star dance
around it center, not much but enough to blur CCD image. I am just starting
and I will have to keep record of my observations. I hope to end up with a
conclusion in a few months.

     Last night, I  took a few CCD shots of magnitude 8-10 stars with sideral
motor turned off. We can see star trails with seeing wobble with time having
a wave form. We can mesure the average amplitude of this wave to measure CCD
seeing. There may be something we can do with this approach. I will
experiment.

     The biggest problem to measure seeing is to use the same star or star
having the same magnitude. We also have to use the same exposure, same
cooling temperature.

     Allan


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[Non-text portions of this message have been removed]

--- In AstronomyWeather@y..., "Bruce L. Gary" <brucelgary@c...>
wrote: >
> If this is true, then Allan Rahill's calculations at the CMC, based
as they
> are on synoptic scale data, might be "capturing" only the
tropopause
> component

I hope Allan replies in detail.

But I know a little of how he does it. His own data, 541
observations of seeing from Dorval Quebec, showed that low
altitude winds had the greatest correlation on telescopic seeing.
(He also saw a correleation to the jet steam,
but it was smaller.) So he uses temperature gradients and
wind-induced turbulence data, but he weights it giving much
weight to low altitude effects.

-ad

Concerning the "atmospheric seeing" forecast challenge:

An observer's experience of "atmospheric seeing" may depend on the
telescope altitude above ground.  According to the following article on the
web, originally published in Astron. Astrophys. Suppl. Ser. 136, 19-25
(either 1998 or 1999)
http://www.edpsciences.com/articles/astro/full/1999/07/ds8110/ds8110.html ,
the lowest 13 meters or so can dominate "seeing" (as measured by image
motion monitors and interpreted in terms of FWHM).  Apparently the
literature shows that there are two main components to seeing: 1)
tropopause related (~11 km at mid-latitudes, ~16 km in tropics), and 2)
bottom of the planetary boundary layer (i.e., interface of PBL with the
ground).

If this is true, then Allan Rahill's calculations at the CMC, based as they
are on synoptic scale data, might be "capturing" only the tropopause
component.  In that case, there might be disappointment with the results of
a network of volunteer observers wishing to validate Allan's seeing
forecasts - regardless of how diligent those observations are.

I hope the seeing forecast problem is more tractable than this, so I'd
appreciate hearing from someone who can correct my "learning curve"
understanding of "seeing."

Bruce L. Gary
Santa Barbara, CA

Are the current seeing forecasts at clear sky clocks using sounding
data from balloon radiosondes? I am just starting off into the world
of "astronomic seeing" and am curious if lifted indices and bulk
richardson numbers are of any use in guesstimating relative seeing
rankings. Also, how would one even start to approximate Refractive
Index Structure Constants with readily available data via the net, if
at all possible?

- thanks

- Shannon Mann

Attila and Allan,

Thanks to both of you for excellent suggestions.  Turning off the
sidereal drive and registering a star track on the CCD strikes me as a
great idea with many possibilities.

Allow me to "think out loud" with the following posting.  These
thoughts are based on my other CCD work (precision photometry).

Observing Procedure:

1) The star used for FWHM analysis should not saturate the CCD.  For
16-bit CCDs without anti-blooming the saturation begins at about
40,000 counts (where maximum counts possible is 65,535).  Use only a
star whose highest counts is lower than that.

2) Do a very careful focus before the exposure.

3) I don't think the CCD temperature setting will matter provided the
cooler's duty cycle is below 90%, for example (so that the CCD
temperature is stable).

4) A standard declination should be used; otherwise the speed of the
star's motion across the CCD will be different on different nights.
Although it will be desireable to also be near zenith it is also
important to have some flexibility on choosing drift speed to
facilitate comparisons with other observers.  Maybe a preferred zenith
angle should be chosen, such as 30 degrees.  With such a goal there's
a circle centered on zenith with a 30 degree radius that spans a 60
degree declination range - which affords a good range of drift rates.

5) Different telescope/CCD configurations have different image scales
["arc/pixel].  This issue may deserve some thought if observations are
to be compared.

Analysis considerations:

1) Track width, such as FWHM, cannot be measured with standard image
analysis software (such as MaxIm DL).  The user will have to manually
probe cross-sections to estimate width.

2) Motion "along track" will cause photons to "pile up" and increase
the counts, and also the opposite.  Thus, there is a means for
extracting motion information in the orthogonal direction, which
could either serve to validate the FWHM measurements or perhaps
replace them (if they're easier to analyze).

3) Analysis of tracks has the great feature that it allows for an
estimate of temporal periodicities.  In other words, if the image
wander is slow the track width and brightness will vary slowly along
the track, etc.  A spectral analysis of temporal variations would even
be possible for the advanced observer.

4) Images are "objective" and could be uploaded to an archive for
others to use.  Eventually someone may write a program to take a FITS
image and automatically perform an analysis of seeing parameters.
(That project might actually interest me!)

5) Objective seeing information might possibly be of use to
atmospheric scientists interested in "waves in the atmosphere" (I'm
one such a person).  Predictions of seeing properties could be tested,
being based on the wind altitude profile, topography, temperature and
vapor density altitude profile, etc.

I guess I'd have to say that the more I think about the possibilities
of using CCDs for monitoring "atmospheric seeing" the more interested
I'm becoming in  it!  Surely, some of the professionals have addressed
this subject.  How do we gain from their experiences?  Before I start
trying to contact them, let's hope somebody in this "group" can help
make that connection.


--- In AstronomyWeather@y..., "Allan Rahill" <allan.rahill@s...>
wrote:
> Hi Gary...
>
> Actually, I am trying to find the best way to corrolate the seeing
forecast
> to CCD applications. Lately, I did only 3 sessions of CCD to look at
the
> result when the seeing was particular good, ie about 4-5/5. What I
found so
> far, despite the diffraction pattern is clearly seen all the time,
(which
> also means if there was a visible planet, we would have seen high
quality
> details all the time), a long CCD exposure gave me stars with about
2 arc
> seconds with my C14. This was a disapointment because I expected a
bit
> smaller star diameter. Despite excellent visual seeing, the star
dance
> around it center, not much but enough to blur CCD image. I am just
starting
> and I will have to keep record of my observations. I hope to end up
with a
> conclusion in a few months.
>
> Last night, I  took a few CCD shots of magnitude 8-10 stars with
sideral
> motor turned off. We can see star trails with seeing wobble with
time having
> a wave form. We can mesure the average amplitude of this wave to
measure CCD
> seeing. There may be something we can do with this approach. I will
> experiment.
>
> The biggest problem to measure seeing is to use the same star or
star having
> the same magnitude. We also have to use the same exposure, same
cooling
> temperature.
>
> Allan
>   -----Message d'origine-----
>   De : Bruce L. Gary [mailto:brucelgary@c...]
>   Envoye : 28 aout, 2002 02:36
>   A : AstronomyWeather@y...
>   Objet : [AstronomyWeather] Seeing for CCD users versus visual
observers
>
>
>   As a CCD user I feel the need for a method of measuring
"atmospheric
>   seeing" that is specifically directed to what a CCD records after
a
>   well-guided long exposure.  On that rare occasion when I observe
visually
> I
>   try to imagine what a CCD would record after a few seconds.  I am
struck
> by
>   how important "image wander" must be, and how unimportant will be
those
>   brief moments of sharp clarity that visual observers wait for.
>
>   Can anyone tell me if a protocol has been developed for assessing
"CD
> seeing"?
>
>   Bruce "StarGeezer" Gary
>   Santa Barbara, CA
>
>
>         Yahoo! Groups Sponsor
>               ADVERTISEMENT
>
>
>
>   To unsubscribe from this group, send an email to:
>   AstronomyWeather-unsubscribe@y...
>
>
>
>   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.

----- Original Message -----

From: Allan Rahill

To: AstronomyWeather@yahoogroups.com

Sent: Wednesday, August 28, 2002 9:43 AM

Subject: RE: [AstronomyWeather] Seeing for CCD users versus visual observers

Hi Gary...

 

Actually, I am trying to find the best way to corrolate the seeing forecast to CCD applications. Lately, I did only 3 sessions of CCD to look at the result when the seeing was particular good, ie about 4-5/5. What I found so far, despite the diffraction pattern is clearly seen all the time, (which also means if there was a visible planet, we would have seen high quality details all the time), a long CCD exposure gave me stars with about 2 arc seconds with my C14. This was a disapointment because I expected a bit smaller star diameter. Despite excellent visual seeing, the star dance around it center, not much but enough to blur CCD image. I am just starting and I will have to keep record of my observations. I hope to end up with a conclusion in a few months.

 

Last night, I  took a few CCD shots of magnitude 8-10 stars with sideral motor turned off. We can see star trails with seeing wobble with time having a wave form. We can mesure the average amplitude of this wave to measure CCD seeing. There may be something we can do with this approach. I will experiment.

 

The biggest problem to measure seeing is to use the same star or star having the same magnitude. We also have to use the same exposure, same cooling temperature. 

 

Allan 

 

-----Message d'origine-----
De : Bruce L. Gary [mailto:brucelgary@...]
Envoyé : 28 août, 2002 02:36
À : AstronomyWeather@yahoogroups.com
Objet : [AstronomyWeather] Seeing for CCD users versus visual observers

As a CCD user I feel the need for a method of measuring "atmospheric
seeing" that is specifically directed to what a CCD records after a
well-guided long exposure.  On that rare occasion when I observe visually I
try to imagine what a CCD would record after a few seconds.  I am struck by
how important "image wander" must be, and how unimportant will be those
brief moments of sharp clarity that visual observers wait for.

Can anyone tell me if a protocol has been developed for assessing "CD seeing"?

Bruce "StarGeezer" Gary
Santa Barbara, CA



To unsubscribe from this group, send an email to:
AstronomyWeather-unsubscribe@yahoogroups.com



Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Not being a CCD photographer I dont know of one. But I know just enought about
the instrumentation to speculate that if one turned off one's drive, exposed
for several minutes, then measured the FWHM width of a star trail,
that should give an accurate estimate of the seeing disk with out
disturbances from drive errors.

I suspect that simple FWHM measurements of tracked or even guided
images would be accurate only for very good drives.

-ad

----- Original Message -----
From: Bruce L. Gary <brucelgary@...>
To: <AstronomyWeather@yahoogroups.com>
Sent: Wednesday, August 28, 2002 2:36 AM
Subject: [AstronomyWeather] Seeing for CCD users versus visual observers


> As a CCD user I feel the need for a method of measuring "atmospheric
> seeing" that is specifically directed to what a CCD records after a
> well-guided long exposure.  On that rare occasion when I observe visually I
> try to imagine what a CCD would record after a few seconds.  I am struck by
> how important "image wander" must be, and how unimportant will be those
> brief moments of sharp clarity that visual observers wait for.
>
> Can anyone tell me if a protocol has been developed for assessing "CD seeing"?
>
> Bruce "StarGeezer" Gary
> Santa Barbara, CA

As a CCD user I feel the need for a method of measuring "atmospheric
seeing" that is specifically directed to what a CCD records after a
well-guided long exposure.  On that rare occasion when I observe visually I
try to imagine what a CCD would record after a few seconds.  I am struck by
how important "image wander" must be, and how unimportant will be those
brief moments of sharp clarity that visual observers wait for.

Can anyone tell me if a protocol has been developed for assessing "CD seeing"?

Bruce "StarGeezer" Gary
Santa Barbara, CA

Allan Rahill of the Canadaian Meterological Center has created
a numerical forecast model for astronomical seeing
(http://www.cmc.ec.gc.ca/cmc/htmls/seeing_e.html). This the
same seeing forecast used by the Clear Sky Clocks
(http://cleardarksky.com/csk)

Allan based his model on of 541 of his own observations with his C14.
So the model is reasonably valid, at least for his home town.
But Allan would like data to validate his model for points
all over North America.

I figure many observers already make note of seeing
conditions in their observing logs. I thought perhaps some
might want to contribute their observations of seeing to a
database that I (foolishly) wrote for the purpose.

The database is on http://cleardarksky.com/so
The observation entry form is lined at the bottom of that page.
The database allows entry of ALPO seeing-scale numbers
and of FWHM star diameters. (I also included two other scales
because I did not wish to pre-scribe which seeing-evaluation
scales observers are actually using.)

The database will be able to process observations as far back as
July 27th. All observations and analysis will be public.
I have the most basic analysis working now, which is to
anotate archived copies of Allan's forecast maps with
observations.

Since I am excited Allan tuning his seeing forecast
to perhaps be as accurate as his amazingly accurate transparency
forecast, I would humbly ask ALPO_Jupiter observes to contribute
to the database.

-ad