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Does a lake help seeing?

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#1 vtornado

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Posted 16 July 2021 - 07:58 AM

Costal areas are many times noted as having great seeing.  Curious,  If I bring my scope to a large lake will it have the same effect

if I look across the lake?  It seems feasible that the lake would have a more even surface temp than land and might make the lower atmosphere

more stable directly above it.     I also suppose a small lake might make things worse, as I might be looking through some updraft/down draft on the other side.

 

Unfortunately I live 30 miles from the southwest bank of lake Michigan, so it is a pain to get there and it has areas not so safe for night time viewing,

and I am looking East which means planets would be rising and not high over the horizon.    But there are other folks who live on the north side

of the lake who could look across the lake when the moon/planets are near the meridian.

 

Any experience with this?

 

VT

 



#2 MartinPond

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Posted 16 July 2021 - 08:25 AM

Some of the best seeing I have experienced 

was over Lake Sebago in Maine, and over the

Atlantic Ocean at Chatham (Cape Cod), Mass.

It isn't always a smooth ride,

but when the situation is "condensing but clear"

(water cooler than the air) with moderate winds at night,

the haze gets swept away and the viewing is nice.

And the lack of light fixtures in one direction, of course. 

 

Under high winds things might be a bit more wiggly near the horizon,

   but it's worth a try always.


Edited by MartinPond, 16 July 2021 - 08:27 AM.


#3 descott12

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Posted 16 July 2021 - 08:26 AM

Many that do solar (not solar system) viewing and imaging report excellent results when out over water. But daytime seeing is a lot different (and worse) than nighttime so not sure if it applies as much.



#4 rhetfield

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Posted 16 July 2021 - 08:27 AM

My experience when I tried it at Lake Superior was that the fog and dew rolled in when it got dark.  There is usually cloud cover building over Lake Michigan too.  Folks on this side of the lake do not notice it so much, but for those of us who originally came from the other side, the lake is a big cloud/precipitation engine.  At any rate, you have a lot further than 30 miles to go to get to a lakeshore away from the light dome.  


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#5 John Boudreau

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Posted 16 July 2021 - 08:34 AM

Have a look at the location of Big Bear Solar Observatory:

 

https://en.wikipedia...lar_Observatory

 

I'd agree that nighttime fog can be an issue at some such locations. A lake in Nova Scotia that I spent some Summers at years ago could have fog issues before midnight, but some times that was delayed until 2 AM or so.


Edited by John Boudreau, 16 July 2021 - 08:43 AM.


#6 Couder

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Posted 16 July 2021 - 09:12 AM

I'm having a problem accepting this, although I know about Big Bear Solar Observatory. We live in a valley, even during the big drought a couple years ago when we come home at night you can see the moisture in the air like a cloud. It is present in the daytime too, I cannot bring any of my scopes to a good focus - from 60MM to 8" refractors, the 12.3" Newtonian, the 12" Classical cassegrain, or the small MAK. Once in a blue moon I can see fairly decent - which was the way it was when we looked at this place and I had the observatory built. It is a little downhill from the house, so I keep a scope in the shop which is a tiny bit better seeing.



#7 Supernova74

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Posted 16 July 2021 - 09:20 AM

Well I’m not sure about that one where’s the evidence to back those claims!? also as i was lead to believe that water creates its own little weather system like fog and mist on the surface, not only that the last thing i would want is mosquitos and insects swarming around while trying to observe.also to note if that was truly the case why hasn’t all the major observatories globally next to water instead of being on a mountain side way up high.


Edited by Supernova74, 16 July 2021 - 09:28 AM.


#8 SandyHouTex

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Posted 16 July 2021 - 09:51 AM

My seeing is usually excellent because I’m 20 miles west of Galveston Bay and 20 miles north of the Gilf of Mexico.

 

Transparency on the other hand, with all of the humidity sucks.



#9 jeffmac

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Posted 16 July 2021 - 10:28 AM

One reason that the seeing can be good over a lake is that you are not looking over the top of any buildings, houses or structures that collect heat during the day and lose it during the night. I have had great seeing over Jordan Lake in NC at times. There are lots of factors that make up good seeing though. Sometimes the seeing was bad at the lake.

#10 vtornado

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Posted 16 July 2021 - 07:29 PM

Hi All, thanks for your replies, I put this in Solarsystem observing because I realize there may be some transparency issues with the water vapor / aerosols.  I was hoping for more laminar air for planetary viewing.

 

I have noticed observing on a driveway is a no-no.   Moving my scope 20 feet to the grass noticably helps.

 

I have noticed that moving to a baseball field helps.  I assume this is because there is 500 ft to the nearest house or road.

 

And I might note that my best view of Jupiter ever was a few years ago when it was high in the sky and the air was

so thick you could cut it with a knife.  82 degrees a 10PM and a dew point in the upper 70s.

 

I was thinking a lake could be really good, maybe worth the trip.  There are not many lakes near me with 1 mile or more

diameter, Except lake Michigan.  That is an arduous trip for me through 30 miles of urban traffic, and many areas are not

safe.  And as mentioned, the orientation is wrong I would be looking down the shore line when planets are nearing the meridian.

 

VT.


Edited by vtornado, 16 July 2021 - 07:42 PM.


#11 Supernova74

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Posted 17 July 2021 - 03:29 AM

Hi All, thanks for your replies, I put this in Solarsystem observing because I realize there may be some transparency issues with the water vapor / aerosols.  I was hoping for more laminar air for planetary viewing.

 

I have noticed observing on a driveway is a no-no.   Moving my scope 20 feet to the grass noticably helps.

 

I have noticed that moving to a baseball field helps.  I assume this is because there is 500 ft to the nearest house or road.

 

And I might note that my best view of Jupiter ever was a few years ago when it was high in the sky and the air was

so thick you could cut it with a knife.  82 degrees a 10PM and a dew point in the upper 70s.

 

I was thinking a lake could be really good, maybe worth the trip.  There are not many lakes near me with 1 mile or more

diameter, Except lake Michigan.  That is an arduous trip for me through 30 miles of urban traffic, and many areas are not

safe.  And as mentioned, the orientation is wrong I would be looking down the shore line when planets are nearing the meridian.

 

VT.

Like anything in astronomy the higher you can get the better!?and personally i cannot see any benefits in observing from a lake will improve things whatsoever unless there is something we don,t know about in having mystical,magical qualities!?

however in most part your on the right path in being able to observe well away from buildings,and any structures that soaks up heat like a sponge.so yes grass would be ok.also something else might be worth mentioning if your a big planetary observer buff!?is puchase something like an ADC (atmospheric,dispersion,correcter) thease also prove effective for visual astronomy for planetary observation.



#12 treadmarks

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Posted 17 July 2021 - 08:39 PM

I'd say definitely yes. The theory is that flat terrain allows wind to flow undisturbed, and the low temperature of the water reduces thermal drafts as well. If you look at Clear Sky Charts you'll see that oceanic locations consistently have better seeing. The wind has to be coming from the body of water for it to help, and ideally your target would be in the direction of that body of water.

 

I'm not sure if a long trip is worth it though. You'd still be at the mercy of high atmosphere turbulence (like the jet stream) and weather - flat terrain is far from a guarantee of good seeing.



#13 Allan Wade

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Posted 17 July 2021 - 09:33 PM

Observing over inland bodies of water at night generally produces poor seeing conditions. The boundary that exists between the water and land produces turbulence from the mixing of rising (warm) and falling (cold) air.

 

I live near a large inland lake. I can get perfect seeing some nights with great planetary detail. But as soon as the planet moves over the influence of the warmer, rising lake air all planetary detail disappears. 
 

Great night time seeing conditions aren’t due to observing near water, but rather observing near flat terrain where the airflow around you is laminar. It just so happens that oceans are pretty flat places that don’t produce turbulent airflow like mountains do. My dark site has thousand of miles of dead flat inland Australia to the west, and hundreds of miles of mountains and hills to the east. When the wind is from the west I get excellent seeing. When it’s from the east I get rubbish seeing.



#14 Dave Mitsky

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Posted 17 July 2021 - 10:01 PM

On the second night of the 1999 Blackwater Falls Astronomy Weekend we were set up outside of where the talks were held.  We had observed from the summit of Spruce Knob the previous night and had a fantastic time.   

 

There was a lake nearby.  Not long after dark the dew and fog began in earnest and before too long even the people with dew zappers were shut down.



#15 Dave Mitsky

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Posted 17 July 2021 - 10:06 PM

Great night time seeing conditions aren’t due to observing near water, but rather observing near flat terrain where the airflow around you is laminar. It just so happens that oceans are pretty flat places that don’t produce turbulent airflow like mountains do.

Laminar air flow is what makes the seeing at the Winter Star Party in the Florida Keys so amazing.



#16 Allan Wade

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Posted 17 July 2021 - 11:01 PM

Laminar air flow is what makes the seeing at the Winter Star Party in the Florida Keys so amazing.

Two of my top three lifetime best eyepiece views have been at the Winter Star Parties. Big dobs and 10/10 seeing is a match made in heaven.


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#17 BSJ

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Posted 19 July 2021 - 12:09 PM

I live on a big island in the middle of Lake Champlain.  Great seeing has been very very rare.  And it's usually worse than locations, off island, that are just a few miles away from the lake.


Edited by BSJ, 19 July 2021 - 12:11 PM.

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#18 Cpk133

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Posted 24 July 2021 - 04:50 PM

Two of my top three lifetime best eyepiece views have been at the Winter Star Parties. Big dobs and 10/10 seeing is a match made in heaven.

Theres more to it than just geography.  Water temp close to air temp = less convection.  Theres a reason gliders dont work so well over large bodies of water.  



#19 Allan Wade

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Posted 24 July 2021 - 08:17 PM

Theres more to it than just geography.  Water temp close to air temp = less convection.  Theres a reason gliders dont work so well over large bodies of water.  

I’ve done a lot of gliding. I know what you mean. Not great places for lift.

The air over large bodies of water remains comparatively stable over the 24 hour cycle. It’s the land that’s the problem. The wild swings in air temperature over the land is what causes the turbulence near the land/water boundary from the horizontal and vertical air flows.


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#20 Redbetter

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Posted 25 July 2021 - 05:51 AM

Seeing effects with lakes are going to be very dependent on the particulars of the terrain, season, and weather patterns of the particular body of water.  I would expect them to be most "ocean like" over the largest lakes:  few obstructions to prevailing air flow, fewer prominent topography-related thermal effects from cooling night air and hot ground.

 

Related to the discussions about gliding thermals, I like to fish for trout in lakes at 8,000 to 10,000 feet.  These are tarn lakes and they have their own air circulation patterns.  In general the air is quite still near sunrise and sunset, but they tend to be breezy during the day.  And the problematic part is that the wind usually blows out more or less radially from the center.  I can walk the shore all around and be catching varying degrees of breeze in my face for 360 degrees.  This puzzled me for a time until I read some explanations that fit what I observed.  The air flow seems to be a sinking column toward the lake, and away from it along its perimeter.  I am not sure how much of this comes from the heating of the partial steep bowls surrounding such lakes, and how much comes from cooling at the lake surface, but the pattern at ground level is identifiable.

 

In the same vein, Steve Fossett is theorized by the NTSB to have met his demise due to the unpredictable diurnal wind patterns related to the geography of the pinnacles and lakes around Minarets in the Sierra Nevada.  He was too low, and without enough power for the conditions.  His ID, some clothing, and a few scattered bones were found about 1 year after he disappeared, along with the wreckage.  Examination of the engine and prop suggested it was making power when it impacted--unfortunately, I can't find an analysis of power output based on the wreckage that links all of this and provides detail other than impact damage descriptions to the engine, which were substantial.




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