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Smoke and 'seeing'

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#1 oldtimer

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Posted 24 September 2020 - 04:20 AM

Lots of smoke here in the midwest (Chicagoland) in the sky lately from the west coast fires. However. maybe it's just me but it seems to steady the seeing for planetary views. Does s anyone else experience this?

 

Gary (oldtimer)



#2 Redbetter

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Posted 24 September 2020 - 05:03 AM

Lots of smoke here in the midwest (Chicagoland) in the sky lately from the west coast fires. However. maybe it's just me but it seems to steady the seeing for planetary views. Does s anyone else experience this?

Here near the origin of some of that smoke...yes, I have noticed the smoke actually improving seeing greatly compared to typical nights here in the Central Valley.  We get a lot of 100+ degree days up through September and we were hitting 111 to 113 F when the fire exploded to produce the largest pyrocumulonimbus ever seen in the U.S.  The seeing in my backyard is generally poor all summer.  No need to set up a scope to confirm, just walk outside and see the rapid twinkle all the way to zenith, go back inside and do something else.  Planetary detail is very limited regardless of aperture from June through September, which is why I skip even doing planetary in the backyard most of the time, and wait to take the big scope up the mountain for seeing that is a notch or two better on average.  I already know what a blurred Jupiter or Saturn look like at low power...

 

But when the smoke was running high in the air column and blanketing us without choking us to death, the temps fell about 15 F below forecast during the heat of the day.  They cooled off at night, but were also somewhat moderated.  Humidity was higher as a result.  The impact on seeing was dramatic despite several magnitudes of dimming.  Twinkling subsided.  This was close to the temp/humidity and seeing conditions I get in the backyard for a good stretch in mid-spring...minus the smoke dimming of course.  As things cleared somewhat, so that a handful of stars could be seen in the suburbs with good dark adaptation, I was able to see more detail on Mars and use higher power than I normally could.  This peaked early when the sky began to clear, then ebbed over several nights as transparency improved, with seeing declining as temperatures began to rise  (even though the jet stream velocities fell several fold.)  It is back to normal now...poor for planetary. 

 

So there has been a silver lining to the smoke, if one was doing planetary or double star observing.  It was a 100% loss for any serious DSO observing.  


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#3 MikiSJ

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Posted 24 September 2020 - 05:06 AM

One of the fires Redbetter is referring to, the Bobcat Fire has become the state's largest ever and is not under complete control. Stay tuned.



#4 Redbetter

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Posted 24 September 2020 - 05:49 AM

While quite large, the Bobcat is not the one I was referring to and is far from the state's largest ever--somewhat surprisingly--it isn't even in the top 20 yet and is shown as a higher percentage control that several larger active fires.  The SQF is still larger and it also isn't in the top 20, although I suspect it will exceed the Rough Fire which the Creek Fire bumped off the top 20 a few weeks ago.   The Creek fire is over twice as large as either the Bobcat or SQF, and is only behind several of the recent complexes (combined fires) in acreage.  The Creek Fire is sitting at #6 presently, and larger than anything in California prior to 2018.   I have seen headlines calling the Creek Fire the state's "largest single fire", but that seems an overstatement since it would be hard to fully separate some of the fires in the complexes in the past year (and the Mendocino 2018 complex which is the only non-2020 fire larger than the Creek.)

 

They have 3,100 personnel on the Creek Fire, and have even brought in the Marines.  This and more favorable weather have resulted in containment in the critical zones.  Now we wait for mop up there, as well as stopping the progression in the back country/wilderness areas.  




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