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Northern hemisphere never get dark enough?

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#1 winterprillan

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Posted 07 November 2018 - 01:14 PM

I live in Sweden, at North 59 degrees. I´ve been traveling around my country to seek for the darkest places to observe the nightsky.

I´ve been in bortle 1,5 as the darkest place, in December when it is at darkest here ( Dark Grey on LP map).

But When my eyes has get used to the dark, the sky is still Dark blue, not black. I can with ease see trees, and stuffs around me on a great distance, and the milky way has about the same structure/brightness as in the Yellow/green zones.

 

Could it be that the sky is much darker in the southern hemisphere than the north, at bortle 1?

 

 

 

 



#2 J A VOLK

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Posted 07 November 2018 - 01:32 PM

In the summer the sun will barely go below the horizon in your location - you have twilight all night, the Bortle scale will not consider this

#3 Astrojensen

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Posted 07 November 2018 - 01:56 PM

The background sky is never completely black from anywhere on Earth, due to natural airglow. Airglow does seem to be pretty (annoyingly) bright in the northern hemisphere and has brightened considerably in recent years. 

 

 

Clear skies!
Thomas, Denmark



#4 Luca Brasi

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Posted 07 November 2018 - 02:21 PM

The border between Utah and Colorado gets pretty dark. I can see Triangulum Galaxy and Uranus with the naked eye on a good night. I've even seen the Heart and Soul Nebulas through my 355mm.

#5 winterprillan

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Posted 07 November 2018 - 02:34 PM

The background sky is never completely black from anywhere on Earth, due to natural airglow. Airglow does seem to be pretty (annoyingly) bright in the northern hemisphere and has brightened considerably in recent years. 

 

 

Clear skies!
Thomas, Denmark

Ok, do you have been in a dark sky far south to compare? I´ve never been far south but in a few years i plan a trip to australia or/and atacama desert in Chile. That will be really interesting to see the difference.

Denmark i think have more LP than Sweden.

How are the sky in Denmark, Better seeing?



#6 winterprillan

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Posted 07 November 2018 - 02:42 PM

The border between Utah and Colorado gets pretty dark. I can see Triangulum Galaxy and Uranus with the naked eye on a good night. I've even seen the Heart and Soul Nebulas through my 355mm.

Never seen m33 naked eye, and i´ve tried. I can see a little difference  between yellow and green zone, the milky way seem a bit brighter and more extended. But i was dissappointed at the Dark grey zone.



#7 Astroman007

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Posted 08 November 2018 - 03:47 PM

But When my eyes has get used to the dark, the sky is still Dark blue, not black. I can with ease see trees, and stuffs around me on a great distance

Although I would not describe the night sky of my somewhat lower latitude as dark blue...in fact, on the very best and darkest of winter or spring nights it is unquestionably very close to black, if not completely black...I can still make out the trees around me to a certain, but not a great, distance. There is still some tiny bit of light from an unknown source, whether natural airglow or indeed the faint light of the hidden sun.



#8 Astroman007

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Posted 08 November 2018 - 03:51 PM

The background sky is never completely black from anywhere on Earth, due to natural airglow. Airglow does seem to be pretty (annoyingly) bright in the northern hemisphere and has brightened considerably in recent years. 

 

 

Clear skies!
Thomas, Denmark

I thought that the natural airglow was particularly noticeable this past summer as opposed to previous years. I am pleased to know that others have seen the same thing. What could account for this brightening of our hemisphere?



#9 Waddensky

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Posted 08 November 2018 - 04:23 PM

Airglow, zodiacal light, integrated starlight and diffuse galactic light are all examples of natural light sources affecting sky brightness. So there's no 'total darkness' when observing from Earth. What light pollution map are you using? Some of them only show light sources and not the effect these sources have on sky brightness. They may become outdated too.
 

I thought that the natural airglow was particularly noticeable this past summer as opposed to previous years. I am pleased to know that others have seen the same thing. What could account for this brightening of our hemisphere?

Airglow is affected by solar activity (sunspot cycle), among other things.


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#10 Arcticpaddler

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Posted 09 November 2018 - 12:08 PM

Never seen m33 naked eye, and i´ve tried. I can see a little difference  between yellow and green zone, the milky way seem a bit brighter and more extended. But i was dissappointed at the Dark grey zone.

Being in a very dark place does not mean the transparency is great on a given night.  I live in the dark blue (Bortle 3) zone, and M33 is a naked eye object on a good night.  I've observed in black zones where M33 could be seen with direct vision on one night, but could not be seen at all on another.  Both nights were clear and very dark.



#11 winterprillan

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Posted 09 November 2018 - 12:42 PM

Airglow, zodiacal light, integrated starlight and diffuse galactic light are all examples of natural light sources affecting sky brightness. So there's no 'total darkness' when observing from Earth. What light pollution map are you using? Some of them only show light sources and not the effect these sources have on sky brightness. They may become outdated too.
 

Airglow is affected by solar activity (sunspot cycle), among other things.

Your right. checked out skyglow. Just wonder also how much global warming affect the sky? We had the warmest summer ever in history of Sweden this year, it was terrible.

I have used this map.

http://darksitefinde...l#4/40.41/-7.47

Do you know a better skymap?



#12 winterprillan

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Posted 09 November 2018 - 12:54 PM

Being in a very dark place does not mean the transparency is great on a given night.  I live in the dark blue (Bortle 3) zone, and M33 is a naked eye object on a good night.  I've observed in black zones where M33 could be seen with direct vision on one night, but could not be seen at all on another.  Both nights were clear and very dark.

Ok, interesting info. 2 black nights with m33 seen and then not.

Some nights are just **** crazy good, they are rare though.

Have you experienced that the milky way cast siluette shadow on the ground?



#13 Astroman007

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Posted 09 November 2018 - 01:52 PM

Have you experienced that the milky way cast silhouette shadow on the ground?

Rarely, but I have, yes. On the very best winter nights...a mere handful of times...I have also observed by naked eye both Barnard's Loop and the halo of vast nebulosity about Meissa, both clearly reddish in color.



#14 JohnAkai

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Posted 14 November 2018 - 03:28 PM

winterprillian, Please follow this link for dark skies information in Chile. https://www.cloudyni...dpost&p=8903808




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