Clear Sky Clock Accuracy

Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

Matt

It says somewhere in the site that the accuracy is about 15 kms IIRC.

I find it's quite accurate the vast majority of the time.


Todd

http://www.backyardastronomy.com
http://www.skynewsmagazine.com
http://www.simpleastrophotography.com

Matt Simmons wrote in message . ..
Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

Matt

CSC uses the Canadian weather model, one of several in use. CSC is
reasonably accurate for a 10-mile diamater centered on the listed
latitude and longitude found at the very bottom of the page under
"techno-geek" stuff. I'd say the forecast for the absence or presence
of clouds is 80-90% accurate, the transparency forecast is about 65%
accurate and the seeing forecast is about 80% accurate. That's for
Northern California.

I've used CSC for several years - even before Attilla Danko created
the "clocks" from the forecast.

Clear skies,
Shneor Sherman

Matt Simmons wrote in message . ..
Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

Matt

I think it's pretty accurate. It has gotten to the point where if I
see a lot of dark blue I have trouble sleeping at night. To see what
happens away from the specific local, just click on the squares and it
gives you the whole map for that time.

Steve O.

"Matt Simmons" wrote in message
news
Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

Matt

Oh yeah, so accurate in fact I'm considering giving up on ever doing
astronomy in Alberta!!

Matt Simmons wrote in message . ..
Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

FWIW, I examine 3-4 sites flanking whatever site for which I'm interested in
knowing its sky conditions.

When I intend to view from my backyard, for example, I examine all of:

http://www.cleardarksky.com/c/EwellObCAkey.html
http://www.cleardarksky.com/c/StanfordCAkey.html
http://www.cleardarksky.com/c/Montebello_CAkey.html
== me ==
http://www.cleardarksky.com/c/SrtgaCAkey.html
http://www.cleardarksky.com/c/SanJoseCAkey.html
http://www.cleardarksky.com/c/OkrdgObCAkey.html
http://www.cleardarksky.com/c/MtHamCAkey.html

Even then, I still examine AWS and other weather sites for there are times
when ClearDarkSky reports my skies are clear yet simply looking up outside
shows total cloud cover over N. California.

If your skies are clear, one should examine:

http://orbit35i.nesdis.noaa.gov/arad/fpdt/tifcsts.html

for its Clear Air Turbulence report; I find the 6-hour view to be the most
useful for me.

"Matt Simmons" wrote in message
news
Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com? How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish? I know, I
know, give me a break, its cloudy, I'm bored.

Matt

It can be pretty accurate. I once got a report that said it would be clear
until 11pm, and then cloudy until 3am. Sure enough, at 11pm, the clouds
rolled in, and most people at the site went home. Instead, I went back to
my car and took a nap until 3am, at which time it was perfectly clear again.

Matt Simmons wrote in message . ..

Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com?

About as accurate or inaccurate as any other weather report.
Certainly a useful tool, but don't take it as gospel.

How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish?

That depends on your location. In a place where weather is
governed by topography, like the California coast, one site
can have has fog 90% of the time while another site two miles
away is clear 90% of the time.

Where I live, weather is mostly a matter of air masses, and it
is pretty imponderable exactly where the boundary between cool
clear air and humid hazy air will lie six hours in the future.
That is why I never use the Clear Sky Clocks, but instead go
to the underlying http://www.cmc.ec.gc.ca/cmc/htmls/mainpage.html,
which shows maps rather than point forecasts. Then if I see
that it is forecast to be clear where I am but cloudy 30 miles
to the west, I can take the forecast with a grain of salt.
But if I see that it is forecast to be clear over my whole
area, it is probably reliable.

- Tony Flanders

"Tony Flanders" wrote in message
...
Matt Simmons wrote in message
. ..

Does anyone know the accuracy of the Clear Sky Clocks at
cleardarksky.com?

About as accurate or inaccurate as any other weather report.
Certainly a useful tool, but don't take it as gospel.

How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish?

That depends on your location. In a place where weather is
governed by topography, like the California coast, one site
can have has fog 90% of the time while another site two miles
away is clear 90% of the time.

Where I live, weather is mostly a matter of air masses, and it
is pretty imponderable exactly where the boundary between cool
clear air and humid hazy air will lie six hours in the future.
That is why I never use the Clear Sky Clocks, but instead go
to the underlying http://www.cmc.ec.gc.ca/cmc/htmls/mainpage.html,
which shows maps rather than point forecasts. Then if I see
that it is forecast to be clear where I am but cloudy 30 miles
to the west, I can take the forecast with a grain of salt.
But if I see that it is forecast to be clear over my whole
area, it is probably reliable.

- Tony Flanders

yep..Canada kicks ass in this particular mode of forecasting . Too bad in
Alberta is has become downright scary to look at 80% of the time!!

Tony Flanders wrote:

How far away from a listed site is the reading
still accurate and at what rate does the accuracy diminish?

That depends on your location. In a place where weather is
governed by topography, like the California coast, one site
can have has fog 90% of the time while another site two miles
away is clear 90% of the time.

Correct, Tony! The weather can change quite a bit in a few miles. The
Mount Wilson Clear Sky Clock is a case in point. The particular speck
of land used for that forecast includes the observatory at 5700 feet and
the valley floor almost 5000 feet below but just a few miles horizontal
distance. When the fog you refer to comes into the valleys your
location on that topography affects your observing conditions quite a
bit!

Mike Simmons