3 replies to this topic

[Maxtrixbass]

Seeing conditions over water have been discussed here, but I have not come across the  the temperature factor between water and air.

 

I live on Puget Sound north of Seattle. A fairly deep seven mile inlet is at the edge of my property about 200 feet away. I am about 100 feet up above the water. When the water temp is warmer than the surrounding air the seeing is absolutely horrible! Its not the buzzy fuzzy of the jet stream, but slow deep waves. It took me awhile to discover the pattern, but I finally realized it was due to heat plumes coming off the water.

 

It may seem obvious, but the local water temp is always between 45-50F. Not exactly warm, but when the air is in the 20s or 30sF the heat rises like over a road in a summer desert. It strange to think of such profound heat waves generated by 45F degrees. Good news is once the air temp rises above the water the heat tends to sink and the waves go away.

 

Obviously our local jet stream can obliterate good seeing, but for those of you looking out over any type of water, especially water that does not freeze,  its something to consider.The seeing with these heat plumes is much much worse that even the worst jet stream nights and if you are close enough to the water, like me, the corrupted seeing can radiate in every direction of the sky.

 

Good news is this corruption goes away when it gets a bit warmer, for me anything above 45F in the winter and 50F in the summer.

Edited by Maxtrixbass, 19 February 2025 - 02:06 PM.

[MisterDan]

-and the body of water need not be large.  Even small streams can "boil" your local (very local) seeing conditions.

 

Cheers and best wishes.

Dan

[PKDfan]

Big Bear solar observatory in California (1.6meter scope) is on a thin road that goes near the center of the lake. Big Bear Lake ?


I hear its steadiness is exemplary.


Edge boundaries of different temperature gradients of different compositions are just plain rotten for steadiness generally.

While a cold sink like a big lawn or large woodland have excellent seeing over them.



CSS
Lance

[Cpk133]

I live about 500ft from Lake St Clair and have first hand experience with lake seeing.  On a number of occasions, I’ve setup and had meh seeing.  Then out of the blue, we’ll get gusty offshore wind, a couple times i was in the house when the trees started whipping around and I’d think to myself “well that was a waste of my time” only to go back outside for a peek before tearing everything down and being gob smacked by the most rock steady super saturated planetary views.  I’m not 100% sure what causes this to occur, I’m assuming theres some thermal gradient between water and land but whatever it is, it brings moist super stable air that strips away all the local thermals from houses, streets and driveways and it’s like magic and it can persist for hours.  It’s magical and knocks down the mosquitos, my favorite time to observe.

Edited by Cpk133, 22 February 2025 - 10:11 AM.