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General Astronomy >> General Observing and Astronomy

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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Seeing Across The USA
      #5754778 - 03/24/13 07:24 PM

We often talk of how dark various locations are, but what about seeing? Now we know about the Florida Keys, and I can tell you about NYC - where the lack of decent seeing perfectly matches that lack of darkness. But what about other areas. Recently I have had the good fortune of accepting a new job in Denver, where I will be moving in a few months. Now this will be a big step up for wrt access to truly dark skies within a few hour drive, but what about seeing? I would be neat to have an ongoing thread commenting on how often the curtain lifts, wrt diffraction limited seeing (which is obviously also a function of aperture) in the various parts of our beautiful country.

Joe


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MikeBOKC
Post Laureate
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Reged: 05/10/10

Loc: Oklahoma City, OK
Re: Seeing Across The USA new [Re: jpcannavo]
      #5754988 - 03/24/13 09:16 PM

I'm not sure you can make the same kind of generalizations about seeing as you can with light pollution. The lights are always on . . . whereas seeing is variable depending on jet stream position, winds aloft, etc.

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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Re: Seeing Across The USA new [Re: MikeBOKC]
      #5755169 - 03/24/13 11:02 PM

Quote:

I'm not sure you can make the same kind of generalizations about seeing as you can with light pollution. The lights are always on . . . whereas seeing is variable depending on jet stream position, winds aloft, etc.




Of course you can. In fact the science of such generalizations has a name: "statistics". Saying, then, that we can't offer statistical generalizations about such multi-determined variables would entail that we can't, for example, make probabilistic/statistical statements about how such things as average temperature, wind speed, humidity, precipitation etc. vary across the country. Obviously we can and do, and there's a name for that endeavor as well.

More to the point, professional astronomers engage in precisely this sort of "meteorology" of seeing when picking sites for observatories, considering data on the frequency of various seeing conditions at a given location.

Perhaps this may not seem an interesting topic for a thread, but please don't presume it to be a conceptual nonstarter.

Joe

Edited by jpcannavo (03/24/13 11:49 PM)


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vsteblina
sage


Reged: 11/05/07

Loc: Wenatchee, Washington
Re: Seeing Across The USA new [Re: jpcannavo]
      #5755189 - 03/24/13 11:17 PM

Well, I am on the east side of Cascades.

Seeing is well....very poor. Nah, not very poor...godawful.

There are a few weather patterns where the seeing improves. I would get to know your weather patterns in Denver and plan your viewing with that in mind.

Yours should be a little better since your farther away from the mountains in Denver.

The good news is get west of Denver up in the mountains and your seeing is probably much better, but somebody from Denver probably has info on this.


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BarbMoore
sage
*****

Reged: 05/11/09

Loc: South central New Mexico
Re: Seeing Across The USA new [Re: vsteblina]
      #5755285 - 03/25/13 12:21 AM

When you move to Colorado, you can always drive south to New Mexico where it's sparsely populated, dark skies, and usually terrific weather.

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Seldom
professor emeritus


Reged: 08/05/12

Loc: N of Cedar City Light Dome
Re: Seeing Across The USA new [Re: BarbMoore]
      #5755390 - 03/25/13 01:45 AM

To get a sense of it I'd check:
http://www.intellicast.com/National/Wind/JetStream.aspx
http://www.cleardarksky.com/c/DenverCOkey.html?1
http://forecast.weather.gov/MapClick.php?map.x=153&map.y=128&site=bou...
http://www.accuweather.com/en/us/colorado/satellite


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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Seeing Across The USA new [Re: jpcannavo]
      #5755583 - 03/25/13 07:13 AM

Seeing correlates crudely with three things: latitude, mountains, and water. Mid-latitudes -- say 40 to 50 in both hemispheres -- tend to have poor seeing due to the jet stream. That includes both New York City and Denver.

Air coming off large bodies of water, such as the Pacific or the Gulf, tends to be thermally stable, favoring good seeing.

Air downwind of mountains (think Denver!) is invariably turbulent, with poor seeing. However, air on the windward side of a mountain range can be quite stable.

Note that winds in the temperate zones almost always blow west to east.


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REC
Post Laureate
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Reged: 10/20/10

Loc: NC
Re: Seeing Across The USA new [Re: Tony Flanders]
      #5755898 - 03/25/13 11:00 AM

"Mid-latitudes -- say 40 to 50 in both hemispheres -- tend to have poor seeing due to the jet stream. That includes both New York City and Denver".

Tony, what is your opinion of 35* where I live in NC?

Thanks!

Bob


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Thomas Karpf
Carpal Tunnel


Reged: 02/09/09

Loc: Newington, CT
Re: Seeing Across The USA new [Re: REC]
      #5755943 - 03/25/13 11:21 AM

To get detailed seeing information...

Start at ClearDarkSky.com. Pick a state and look at the LIST, not the MAP. Click on a site that has a STAR in the left column. A star indicates that someone is paying to sponsor the site (a dollar a week minimum, no minimum number of weeks); there are a whopping six sites in Colorado that are sponsored. Once a site is sponsored, the FORECAST HISTORY/CLIMATE calculations will be done and the link below will show up WHILE THE SITE IS SPONSORED.

Click on FORECAST HISTORY/CLIMATE and scroll down to SEEING.


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MikeBOKC
Post Laureate
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Reged: 05/10/10

Loc: Oklahoma City, OK
Re: Seeing Across The USA new [Re: jpcannavo]
      #5756047 - 03/25/13 12:09 PM

Certainly you are correct, as other posters have noted -- there are locations where on any given night seeing is more likely to be good or poor based on long term atmospheric trends or geographical features (water, mountains, etc.) However my original point in response to an ineresting inquiry was that while the light pollution maps don't change much, if at all, over time (Manhattan will be a white zone bordering on ridiculous until the apocalypse) there are still going to be seaosnal and even daily and hourly variables in seeing. Bottom line: I would be more inclined to move somewhere for astronomical purposes based on the Bortle ratings there than on an analysis over time of the CSC seeing forecast, which can go from blue to white and back again in 24 hours.

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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Seeing Across The USA new [Re: REC]
      #5756190 - 03/25/13 01:13 PM

Quote:

Tony, what is your opinion of 35* where I live in NC?




Hey -- you tell me, not the other way around! Seeing varies constantly from one night to the next, and I haven't spent enough time in NC to judge it.


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Mxplx2
sage


Reged: 09/12/12

Loc: NE PA USA
Re: Seeing Across The USA new [Re: jpcannavo]
      #5756231 - 03/25/13 01:58 PM

I live on the east coast. On a trip to California, most notably Napa Valley, the clarity of the air was STUNNING! A view of mountains in a lot of places in California puts them almost in your lap, compared to Pennsylvania where you see them through somewhat of a haze. With weather traveling west to east for the most part, by time air gets to us it's had "additives" like human effluent, moisture, etc.

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Tom Polakis
Carpal Tunnel
*****

Reged: 12/20/04

Loc: Tempe, Arizona
Re: Seeing Across The USA new [Re: Mxplx2]
      #5756689 - 03/25/13 05:51 PM

Quote:

I live on the east coast. On a trip to California, most notably Napa Valley, the clarity of the air was STUNNING! A view of mountains in a lot of places in California puts them almost in your lap, compared to Pennsylvania where you see them through somewhat of a haze. With weather traveling west to east for the most part, by time air gets to us it's had "additives" like human effluent, moisture, etc.





The O.P. is asking about seeing, though, which has very little correlation with visibility. Which areas of the country have steadier views through the telescope?

Note that steadiness as seen through a telescope often has little correlation with naked-eye twinkling of stars. It's pretty common in my back yard to have almost no visible twinkling and 5-arcsecond seeing.

Here in Arizona, small hilltops above the surrounding terrain in the northern half of the state have remarkably good seeing. A lot of seeing data was gathered for the Discovery Channel Telescope site before putting a 4-meter telescope up there. The location is only a couple hundred feet above the surroundings, with a nice cliff in the direction of the the prevailing southwesterly wind.

Tom


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Re: Seeing Across The USA new [Re: Thomas Karpf]
      #5756989 - 03/25/13 08:51 PM

Quote:

To get detailed seeing information...

Start at ClearDarkSky.com. Pick a state and look at the LIST, not the MAP. Click on a site that has a STAR in the left column. A star indicates that someone is paying to sponsor the site (a dollar a week minimum, no minimum number of weeks); there are a whopping six sites in Colorado that are sponsored. Once a site is sponsored, the FORECAST HISTORY/CLIMATE calculations will be done and the link below will show up WHILE THE SITE IS SPONSORED.

Click on FORECAST HISTORY/CLIMATE and scroll down to SEEING.




Tom
I have been using CSCs for quite some time, but was not aware of this particular feature for sponsored sites. Very, very cool!!!
Joe


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Re: Seeing Across The USA new [Re: Tom Polakis]
      #5756999 - 03/25/13 08:59 PM

Quote:

Quote:

I live on the east coast. On a trip to California, most notably Napa Valley, the clarity of the air was STUNNING! A view of mountains in a lot of places in California puts them almost in your lap, compared to Pennsylvania where you see them through somewhat of a haze. With weather traveling west to east for the most part, by time air gets to us it's had "additives" like human effluent, moisture, etc.





The O.P. is asking about seeing, though, which has very little correlation with visibility. Which areas of the country have steadier views through the telescope?

Note that steadiness as seen through a telescope often has little correlation with naked-eye twinkling of stars. It's pretty common in my back yard to have almost no visible twinkling and 5-arcsecond seeing.

Here in Arizona, small hilltops above the surrounding terrain in the northern half of the state have remarkably good seeing. A lot of seeing data was gathered for the Discovery Channel Telescope site before putting a 4-meter telescope up there. The location is only a couple hundred feet above the surroundings, with a nice cliff in the direction of the the prevailing southwesterly wind.

Tom




Tom
I have noticed this poor correlation as well. There have been a number of times where naked eye stars in NYC are so still they look like planets. So I run in and grab my 100 mm ED (hoping it will be worth bringing out the big guns) and lo and behold, the same old Pickering 4 or worse!
Joe


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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Seeing Across The USA new [Re: Tom Polakis]
      #5757000 - 03/25/13 08:59 PM

Quote:

I would be more inclined to move somewhere for astronomical purposes based on the Bortle ratings there than on an analysis over time of the CSC seeing forecast...




Precisely. Predicting seeing is much the same as predicting weather; we're gettin' better at it, fersure, but it's still fraught with inaccuracies.

Even so, if i had a choice in the matter, i'd try to pick a place to live (near) that had the weather variables that would tend to toward better seeing. As it is, my seeing is pretty decent, generally... yet those weather conditions that tend to favor it ALSO favor a marine layer much of the (&%$@ $@&%) time.

Ya pays yer money, and ya takes yer chances...


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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Seeing Across The USA new [Re: jpcannavo]
      #5757021 - 03/25/13 09:09 PM

Quote:

There have been a number of times where naked eye stars in NYC are so still they look like planets.



The other aspect to this is that our "built-environment" tends to be a giant heat-sink, where materials like pavement, walls & roofs, attics loaded with hot air, and fire-breathing mechanical equipment marinate the local environment! This itself creates a micro-climate of poor seeing. It also means large optics, especially those slung low to the ground like a Dob, seem to NEVER reach ambient temps even tho the air may be finally getting there.

Not all 'seeing' is determined by the jetstream! Getting into the "green", as well as being positioned to avoid viewing over (or thru) such a heat-dome, can go a lonnnnng ways toward realizing better 'seeing'.


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Re: Seeing Across The USA new [Re: Mike B]
      #5757526 - 03/26/13 05:41 AM

Quote:

Quote:

I would be more inclined to move somewhere for astronomical purposes based on the Bortle ratings there than on an analysis over time of the CSC seeing forecast...




Precisely. Predicting seeing is much the same as predicting weather; we're gettin' better at it, fersure, but it's still fraught with inaccuracies.

Even so, if i had a choice in the matter, i'd try to pick a place to live (near) that had the weather variables that would tend to toward better seeing. As it is, my seeing is pretty decent, generally... yet those weather conditions that tend to favor it ALSO favor a marine layer much of the (&%$@ $@&%) time.

Ya pays yer money, and ya takes yer chances...





But there is a distinction between predicting seeing as in: "we can expect a lovely weekend with Pickering 7 seeing this Friday night..." and generalizations about seeing as in the claim that the Florida Keys is more likely to blow away the North East for high power planetary observing. You wont find Christopher Go or Anthony Wesley hauling their equipment to upstate New York for the next planetary opposition!

Agree with your comments about seeing micro-environments. Without digressing into another "this scope vs. that" debate, the close to the ground location of the primary can be a problem for dobs.
Joe


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Seeing Across The USA new [Re: Tom Polakis]
      #5757671 - 03/26/13 08:25 AM

Quote:

Note that steadiness as seen through a telescope often has little correlation with naked-eye twinkling of stars. It's pretty common in my back yard to have almost no visible twinkling and 5-arcsecond seeing.




Tom:

At first I thought maybe you had meant 0.5 arc-second seeing.

I have to think San Diego has significantly better than average seeing. Generally south of the jet streams and with mild winds blowing off the Pacific, it is generally quite steady. Splitting a 1 arc-second double is pretty typical.

Of course if the wind turns around and blows across the mountains from the east.. not good, clear but turbulent.

Jon


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hfjacinto
I think he's got it!
*****

Reged: 01/12/09

Loc: Land of clouds and LP
Re: Seeing Across The USA [Re: Jon Isaacs]
      #5757761 - 03/26/13 09:32 AM

I live in NJ (14 miles west of NYC) so we have lots of light pollution but seeing is weird. When I go to Jenny Jump, the seeing tends to be poorer than at home. Jenny Jump is 1100 feet high so that maybe an issue. At home I am downward of the the Watchung hills but on a slight ridge compared to other areas of town.

At Union County College, I have on various days been able to use 500 magnification without incident. I think the reason for being able to use that much power is we are surrounded by tall trees to the west, east and north and a small lake to the south. This seems to keep the air slightly more stable than in other places.

I once set-up on Sandy Hook by the atlantic and seeing was pretty bad as you have the constant wind off the ocean.

I think if you look around you can find areas in which the seeing is good.


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