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seeing conditions better after rain

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#1 skywatcher01

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Posted 11 August 2020 - 06:16 PM

Hi

 

I am new in astronomy, but I just realized  that in hot summer days ( 35 Celsius ), i have better seeing conditions on planets (Saturn ) with my Dob after rain, when temperature goes down.

Saturn is sharp in this conditions in my location ( Latitude‎: ‎48° )


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#2 Migwan

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Posted 11 August 2020 - 07:16 PM

Sometimes right after a cold front, it does just that.   The jet stream being so far up north much of this summer, at least relative to Michigan, also helps.    

 

On the other hand,  the best non-winter seeing conditions that I have experienced here came with the first two heat waves this summer.  Other than the jet being way up to the Hudson Bay, I haven't a clue why.   I should note that I have only four years experience with telescope, so this circumstance might not be new.

 

jd 



#3 photoracer18

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Posted 11 August 2020 - 07:21 PM

Best time is heavy still air in a pre-fog condition. the still air being the key. In the 45 years I lived in MD it only happened once. Lucky for me it was during the 2005 Mars Opposition when both my 6" F15 refractor and my early C-9.25 both reached nearly 600x.



#4 skywatcher01

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Posted 11 August 2020 - 08:13 PM

Hi Photoracer, You mentioned Mars... 

Only thing I see on mars is red ball :)  nothing else,  It has too much reflections, so I used moon filter,

I can see only ball from orange to red, nothing else, 

Before I tried also all color filters I had, but no change.

Today I used 4,5mm eyepiece with 1200 focal lenght == 266 magn.



#5 skywatcher01

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Posted 11 August 2020 - 08:29 PM

Best time is heavy still air in a pre-fog condition. 

Hi, I am not sure what condition have you meant,  but from my perspective also temperature is the key.

Too warm temp (25+Cels. is not good for seeing),  For example this night was 19 Celsius, and was better view.



#6 luxo II

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Posted 11 August 2020 - 08:37 PM

Clearest of all is when the sky clears after a thunderstorm, not only does the rain lay the dust on the ground, thunderstorms bring strong downdrafts of clean, cold air.

 

Here on a hot summer afternoon (can exceed 40 C) a good thunderstorm can bring a temperature drop of 10 degrees C or more.


Edited by luxo II, 11 August 2020 - 08:40 PM.

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#7 skywatcher01

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Posted 12 August 2020 - 05:36 AM

Exactly, this is my experience.



#8 Tony Flanders

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Posted 12 August 2020 - 05:46 AM

Clearest of all is when the sky clears after a thunderstorm, not only does the rain lay the dust on the ground, thunderstorms bring strong downdrafts of clean, cold air.

 

Here on a hot summer afternoon (can exceed 40 C) a good thunderstorm can bring a temperature drop of 10 degrees C or more.

Quite so. But that's a matter of transparency, not seeing. In general, rapid shifts in temperature almost always cause bad seeing -- at least in my part of the world.


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#9 BrettG

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Posted 12 August 2020 - 07:29 AM

I had the best views of Jupiter and Saturn that I ever remember having last week, the night after Isaias blew through.  It came through Tuesday, and Wednesday night was an amazing night.

 

It has been hot garbage since then, but that's a different story.



#10 Tony Flanders

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Posted 12 August 2020 - 10:27 AM

It's curious; I have not noticed any negative correlation between heat and good seeing. In fact my best seeing tends to occur on fairly hot nights, but I'm not sure there's a causal relationship there.

 

Are all these cases of poor seeing on hot nights in urban or rural environments? Having lots of concrete and asphalt around certainly isn't conducive to good seeing, and I can imagine that effect might be exacerbated in hot weather.


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#11 epee

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Posted 12 August 2020 - 03:49 PM

Best seeing I ever experienced in the Coastal SouthEast was along a salt marsh estuary on a warm evening in early October. You could see the fog lifting from the estuary and the humidity was so thick that the dew sounded like rain on the tent. Jupiter looked like a Hubble photo and I ran out of tracking ability well before I ran out of magnification...

Point is, no pavement or roofs, very still, warm rising air, edging toward foggy...


Edited by epee, 12 August 2020 - 03:50 PM.



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