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General Astronomy >> General Observing and Astronomy

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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Transparency is NOT Seeing
      #5761267 - 03/27/13 08:42 PM

Rant over in thread title.

Dave


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skinnyonce
super member
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Reged: 03/23/11

Loc: ohio
Re: Transparency is NOT Seeing new [Re: Cotts]
      #5761270 - 03/27/13 08:44 PM

Ok then

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rdandrea
Carpal Tunnel
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Reged: 06/13/10

Loc: Colorado, USA DM59ra
Re: Transparency is NOT Seeing new [Re: Cotts]
      #5761278 - 03/27/13 08:49 PM

Quote:

Transparency is NOT Seeing




Yep.


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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: Transparency is NOT Seeing new [Re: rdandrea]
      #5761327 - 03/27/13 09:13 PM

Is.

Pete


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FirstSight
Duke of Deneb
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Reged: 12/26/05

Loc: Raleigh, NC
Re: Transparency is NOT Seeing new [Re: azure1961p]
      #5761339 - 03/27/13 09:22 PM

The other night, for example.

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Adam S
scholastic sledgehammer
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Reged: 12/21/05

Loc: Gunnison, Colorado
Re: Transparency is NOT Seeing new [Re: Cotts]
      #5761464 - 03/27/13 10:36 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.

Edited by Adam S (03/27/13 10:46 PM)


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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Transparency is NOT Seeing new [Re: Adam S]
      #5761565 - 03/27/13 11:54 PM

Quote:

...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.


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


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ThreeD
Pooh-Bah


Reged: 12/23/08

Loc: Sacramento suburbs
Re: Transparency is NOT Seeing new [Re: Adam S]
      #5761667 - 03/28/13 01:40 AM

Quote:

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.


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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: Transparency is NOT Seeing new [Re: ThreeD]
      #5761824 - 03/28/13 07:18 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


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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: Transparency is NOT Seeing new [Re: azure1961p]
      #5761884 - 03/28/13 08:04 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


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BillFerris
Post Laureate
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Reged: 07/17/04

Loc: Flagstaff, Arizona, USA
Re: Transparency is NOT Seeing new [Re: Cotts]
      #5761927 - 03/28/13 08:50 AM

and darkness is not transparency. Rant over in reply

Bill in Flag


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: Transparency is NOT Seeing new [Re: BillFerris]
      #5762081 - 03/28/13 10:00 AM

I want good transparency now to go galaxy hunting:)

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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Transparency is NOT Seeing new [Re: Cotts]
      #5762209 - 03/28/13 11:15 AM

Quote:

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?


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REC
Post Laureate
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Reged: 10/20/10

Loc: NC
Re: Transparency is NOT Seeing new [Re: Mike B]
      #5762481 - 03/28/13 02:07 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:)


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BillFerris
Post Laureate
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Reged: 07/17/04

Loc: Flagstaff, Arizona, USA
Re: Transparency is NOT Seeing new [Re: Mike B]
      #5762483 - 03/28/13 02:07 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

Quote:

Quote:

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?




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jeff heck
Pooh-Bah
*****

Reged: 01/16/06

Loc: stl,mo.
Re: Transparency is NOT Seeing new [Re: BillFerris]
      #5762596 - 03/28/13 03:27 PM

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

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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: Transparency is NOT Seeing new [Re: BillFerris]
      #5762623 - 03/28/13 03:49 PM

Quote:

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


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bunyon
Post Laureate
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Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Transparency is NOT Seeing new [Re: REC]
      #5762625 - 03/28/13 03:51 PM

Quote:

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.


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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Transparency is NOT Seeing new [Re: BillFerris]
      #5762638 - 03/28/13 04:05 PM

Quote:

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!


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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: Transparency is NOT Seeing new [Re: BillFerris]
      #5762755 - 03/28/13 05:21 PM

Yep, that's another good indicator!

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