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Transparency is NOT Seeing

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#1 Cotts

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Posted 27 March 2013 - 07:42 PM

Rant over in thread title.

Dave

#2 skinnyonce

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Posted 27 March 2013 - 07:44 PM

Ok then

#3 rdandrea

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Posted 27 March 2013 - 07:49 PM

Transparency is NOT Seeing



Yep.

#4 azure1961p

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Posted 27 March 2013 - 08:13 PM

Is.

Pete

#5 FirstSight

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Posted 27 March 2013 - 08:22 PM

The other night, for example.

#6 Adam S

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Posted 27 March 2013 - 09:36 PM

The water in the stream can be crystal clear and free of particulate matter;however, if there are ripples on the surface the bottom of the stream will appear distorted providing an unpleasant view.

#7 Mike B

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Posted 27 March 2013 - 10:54 PM

...providing an unpleasant view.


Oh, i dunno... have always thot the rippling appearance of the rocks under-water in the streambed was kinda cool.

Now, when applied to the rocks aloft, in the night sky... not so much.
:grin:

But yes- is an excellent illustration of what's hap'nin'. ;)

#8 ThreeD

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Posted 28 March 2013 - 12:40 AM

The water in the stream can be crystal clear and free of particulate matter;however, if there are ripples on the surface the bottom of the stream will appear distorted providing an unpleasant view.

But I'd rather have a view of the bottom that is distorted than have the water be muddy and not see the bottom at all.

I spend most of my time looking for soft patterns of ripples in small sandy areas rather than looking for minute color details on individual rocks or trying to resolve a small gap between adjacent pieces of gravel. While I want both clear and unperturbed water, when looking at sandy areas I can deal with some surface motion so long as the water is crystal clear.

#9 azure1961p

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Posted 28 March 2013 - 06:18 AM

I was kidding with my first post but often the clearest high transparency nights are not the best seeing rather those muggy heat wave summer nights where the stars are even dimmed a but with summer haze yield still seeing clarity that's jaw dropping. I have NEVER experienced similar fantastic seeing in a cool transparent night. Best seeing those kinda nights tops around 7-8 and all too rare. Best seeing in summer is 8-10 and far more frequent.

Pete

#10 Cotts

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Posted 28 March 2013 - 07:04 AM

Hi, Pete. Your experience is similar to mine. I remember the best night of seeing I can recall here in S. Ont. when I first split Antares at Starfest with my 4" Televue Genesis many years ago. It was warm, so humid that the hair dryers were roaring all over the observing field, there were thunderstorms nearby and lightning flashes. The deep sky guys had packed up - no galaxies that night. And the diffraction patterns were motionless!! Perfect 10/10 seeing - still the only time I've experienced that kind of seeing outside of the Florida Keys.

Transparency is about the degree to which the atmosphere dims the image due to humidity, dust, thin cloud, smoke, contrails, particulate matter and what have you. The amount of light getting through, I suppose.

Seeing is about the motion of the atmosphere due to varying density/temperature layers, turbulence, wind shear etc. which affects fine detail in the telescope. The quality of light getting through... Do you see a diffraction pattern, a fuzzball or a speckled pattern.

The words 'clear' and 'clarity' can be (and are) frequently used to describe either of the above so it is often unclear what the speaker/writer is really describing.

We expect incredible precision in our scopes' optics - let's all try for some precision in our use of astronomical terms.

Dave

#11 BillFerris

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Posted 28 March 2013 - 07:50 AM

and darkness is not transparency. Rant over in reply ;)

Bill in Flag

#12 REC

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Posted 28 March 2013 - 09:00 AM

I want good transparency now to go galaxy hunting:)

#13 Mike B

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Posted 28 March 2013 - 10:15 AM

Transparency is about the degree to which the atmosphere dims the image due to humidity, dust, thin cloud, smoke, contrails, particulate matter and what have you. The amount of light getting through, I suppose.


I've often thot that the "blueness" of the sky during the day is a measure of the air's "transparency", and if unchanged into the night, would yield the better deepsky views.

Is this a fair analysis?

#14 REC

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Posted 28 March 2013 - 01:07 PM

Yeah, always used that asumption from when I was a kid just starting out, most times it seems to work....BUT I have seen those deep blue skies all day just to give way to clouds after sunset!

Also I use a small mountain in the distance from where I live and if I can see the tree detail I know it's going to be a good scope night:)

#15 BillFerris

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Posted 28 March 2013 - 01:07 PM

Typically, the deeper the blue of a daytime sky, the less water vapor and other particulates are in the atmosphere. Another way of gauging transparency during the day is the area around the sun which appears washed out & white. the smaller that area--the nearer the deep blue sky wraps around the sun--the better the transparency. Jet contrails are another indicator. Shorter or non-existent contrails can be an indicator of dry air in the upper atmosphere. Water vapor satellite imagery is a good forecast tool. If a large pocket of red/orange air is moving into the area, transparency should improve.

Bill in Flag

Transparency is about the degree to which the atmosphere dims the image due to humidity, dust, thin cloud, smoke, contrails, particulate matter and what have you. The amount of light getting through, I suppose.


I've often thot that the "blueness" of the sky during the day is a measure of the air's "transparency", and if unchanged into the night, would yield the better deepsky views.

Is this a fair analysis?



#16 jeff heck

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Posted 28 March 2013 - 02:27 PM

I look for transparency at the beach, which is all about good seeing! :grin:

#17 Cotts

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Posted 28 March 2013 - 02:49 PM

and darkness is not transparency. Rant over in reply ;)

Bill in Flag


Absolutely, Bill. You can get ridiculous SQM readings in the 24.0 mag/sq.arcsec range in a darkened basement closet but there will be no stars...

My club's dark sky site, Oak Heights, 80 miles east of Toronto, gets SQM's of 21.4 at best and has no large light domes while the Winter Star Party typically gets 21.3 with two large light domes and, yet, the zodiacal light is easy on most clear nights in the Keys while it is rarely, if ever seen at Oak Heights.....

So three parameters to worry about, then. Transparency, Seeing and Darkness.....

Dave

#18 bunyon

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Posted 28 March 2013 - 02:51 PM

Yeah, always used that asumption from when I was a kid just starting out, most times it seems to work....BUT I have seen those deep blue skies all day just to give way to clouds after sunset!

Also I use a small mountain in the distance from where I live and if I can see the tree detail I know it's going to be a good scope night:)



I use Pilot Mountain - is that the one you're talking about? There is a stretch of my drive home where I have it in view for a while. It gives a pretty good estimate of transparency and seeing at ground level which, more often than not, translates to up.

#19 Mike B

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Posted 28 March 2013 - 03:05 PM

Shorter or non-existent contrails can be an indicator of dry air in the upper atmosphere.



And when you see lonnnnng contrails that maintain their shape over great distances, that means steady air at that altitude... quite possibly a help for seeing!

#20 REC

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Posted 28 March 2013 - 04:21 PM

Yep, that's another good indicator!

#21 panhard

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Posted 29 March 2013 - 05:44 PM

Now now Jeff don't get excited. :rofl2:

#22 GOLGO13

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Posted 29 March 2013 - 09:36 PM

I had terrible transparency today. Combine that with terrible light pollution and the get a whole lot of viewing Jupiter ;)

This seemed to be accurate today! Says below average and I agree http://cleardarksky....lObILkey.html?1

#23 Starman1

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Posted 06 April 2013 - 12:49 AM

Normally, Seeing and Transparency are inversely related.
[Edit: I prefer the term Clarity instead of Transparency, because in the common lingo, Transparency also connotes Darkness, which is a different thing entirely.]
One every few years, though, I find myself observing on a night where both are maximally good.
When that happens to be also at a dark site............
Magic!

#24 rookie

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Posted 09 April 2013 - 12:17 AM

Seeing can be quantified by more than casual observation of contrails. Weather balloon data is public information and gathered twice per day at 00:00 and 12:00 UTC when balloons are released around the world. The data for each balloon is usually posted 2-2 1/2 hours later when its flight is completed. For me this is around 9:00 pm EDT. Therefore, you can access current information near your home or observing location by selecting the nearest weather balloon release site. NOAA/ESRL Data Base. The data from weather balloons becomes the foundation for weather forecasting.

Suggestion for sorting and selecting information:
III. station data by state -> continue data request
IV. highlight state of interest on following page
View/Select Stations from state you have selected "Yes"
Will bring up a list of all stations that release balloons in that state. Just highlight and continue data selection.

The numbers are a bit daunting and you should review the FSL Output Format Description to make sense of it all. Once familiar, it's quite easy. There are plotable grafts available too.

FYI, NOAA also has a iPhone app available that is user friendly called RAOB. The phone screen is a bit small for the data and grafts for my eyes.

By reviewing the data, you can actually see wind direction, speed, at elevations from ground level up to about 100,000 feet, depending on when the balloon shatters. It's never exactly the same elevation, but 100,000 Ft is an acceptable average. Airplanes only fly around 30,000 feet so it does not really reveal that much information. Those air masses can sometimes be stable and higher winds can be streaming at opposite directions of 100+knots as has been the case here for the past week.

You can review the data before you observe or correlate it with your "seeing". You might even expect transparency degradation issues when the dew point and temperature data are similar.

I've brought up accessing weather balloon data before, but it does not seem to be used very much by astronomers, and I'm not sure why. At the very least, I have found it interesting and predictive.

When you see the data, it's no mystery why the stars twinkle.






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