Author Topic: Mostly Clear vs Clear  (Read 687 times)

calfkommomu

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Mostly Clear vs Clear
« on: December 25, 2017, 09:22:46 AM »
When you reside in a light polluted area it is an issue.  Here are two pictures of similar vulnerability, one with a mainly clear skies based on most of the weather websites I visit, and one completely apparent.  You can see that 5 percent or less of all cloud opacity can considerably bounce the light back at you.Attached Thumbnails






vieproltesro

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Re: Mostly Clear vs Clear
« Reply #1 on: December 27, 2017, 03:08:43 PM »
Wow! Something for me to try... You could actually determine how different conditions affect observing, like humidity.

Cesar Lawhorn

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Re: Mostly Clear vs Clear
« Reply #2 on: December 28, 2017, 12:02:48 AM »
On Earth, no such thing as completely clear.

Maybe on the Moon.

agtofonist

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Re: Mostly Clear vs Clear
« Reply #3 on: December 30, 2017, 11:32:18 AM »
Quote
On Earth, no such thing as completely clear.

Maybe on the Moon.

Definition of completely clear: I see no clouds, there are no clouds

In other words: there are clouds, but I don't see them, so they don't exist.

teirazaro

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Re: Mostly Clear vs Clear
« Reply #4 on: December 30, 2017, 01:50:58 PM »
Yes, it makes a huge difference as your images show and I only do visual observing. Even for solar the impact is heavy.

reobladvasys

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Re: Mostly Clear vs Clear
« Reply #5 on: January 08, 2018, 01:52:47 PM »
Quote
Quote

On Earth, no such thing as completely clear.

Maybe on the Moon.

Definition of completely clear: I see no clouds, there are no clouds

In other words: there are clouds, but I don't see them, so they don't exist.
It's just before twilight. I have seen no clouds during the night. Twilight increases and now the sunlight illuminates some high clouds that somehow miraculously appeared in the last few minutes.

In other news....

Matthew Danielson

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Re: Mostly Clear vs Clear
« Reply #6 on: January 09, 2018, 07:29:11 PM »
Quote
It's just before twilight. I have seen no clouds during the night. Twilight increases and now the sunlight illuminates some high clouds that somehow miraculously appeared in the last few minutes.

In other news....
Don't worry, the night's over and there's no more observing to do.

flasattecof

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Re: Mostly Clear vs Clear
« Reply #7 on: January 09, 2018, 08:00:05 PM »
Quote
Quote

It's just before twilight. I have seen no clouds during the night. Twilight increases and now the sunlight illuminates some high clouds that somehow miraculously appeared in the last few minutes.

In other news....
Don't worry, the night's over and there's no more observing to do.
http://www.solarastronomy.org/

synchanrimyp

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Re: Mostly Clear vs Clear
« Reply #8 on: January 10, 2018, 05:36:27 PM »
Quote
Quote

Quote

It's just before twilight. I have seen no clouds during the night. Twilight increases and now the sunlight illuminates some high clouds that somehow miraculously appeared in the last few minutes.

In other news....
Don't worry, the night's over and there's no more observing to do.
http://www.solarastronomy.org/
Uhh....

Go to sleep, you need it. It'll help you as you wait for it to get near the meridian.

ziecouvicog

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Re: Mostly Clear vs Clear
« Reply #9 on: January 10, 2018, 06:48:48 PM »
Quote
Quote

It's just before twilight. I have seen no clouds during the night. Twilight increases and now the sunlight illuminates some high clouds that somehow miraculously appeared in the last few minutes.

In other news....
Don't worry, the night's over and there's no more observing to do.
http://www.solarastronomy.org/[/quote]
Uhh....

Go to sleep, you need it. It'll help you as you wait for it to get near the meridian.[/quote]
http://www.collectiv...-is-not-needed/

David Lipson

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Re: Mostly Clear vs Clear
« Reply #10 on: January 12, 2018, 05:26:20 AM »
Still need to wait for it get near the meridian.

redoroto

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Re: Mostly Clear vs Clear
« Reply #11 on: January 12, 2018, 07:44:59 AM »
Quote
Still need to wait for it get near the meridian.

Everyone's observing site and micro-climates are a little bit different. By noon the Sun will have heated up the atmosphere and the ground.

naiciareamu

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Re: Mostly Clear vs Clear
« Reply #12 on: January 12, 2018, 12:11:34 PM »
The difference between those two images does not derive from the presence or lack of cloud outside the frame. It results from the difference in the quantity of water vapor and/or pollutants. Under a clean atmosphere, between any clouds which might be hanging about the sky will nonetheless be nice and dark as allowed by light pollution. In other words, sucker holes in a clean airmass are far better than a cloudless but 'dirty' airmass, as regards transparency and sky darkness.

inuninab

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Re: Mostly Clear vs Clear
« Reply #13 on: January 13, 2018, 05:51:15 AM »
Quote
The difference between those two images does not derive from the presence or lack of cloud outside the frame. It results from the difference in the quantity of water vapor and/or pollutants. Under a clean atmosphere, between any clouds which might be hanging about the sky will nonetheless be nice and dark as allowed by light pollution. In other words, sucker holes in a clean airmass are far better than a cloudless but 'dirty' airmass, as regards transparency and sky darkness.

I see more stars in the upper photo than in the lower photo.

Adam Rice

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Re: Mostly Clear vs Clear
« Reply #14 on: January 18, 2018, 12:08:25 AM »
https://en.wikipedia.org/wiki/Cloud
<p class="citation">Quote

I see more stars in the upper photo than in the lower photo.
[/quote]
I have to disagree with you perhaps your eyesight is not very keen, but if you look at the lower photo you can see crisp dots of starlight, some barely as bright as the background sky, but in the upper photo, merely some smears of the brighter ones.