APOD: Reflecting the ISS (2020 May 28)

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APOD: Reflecting the ISS (2020 May 28)

Post by APOD Robot » Thu May 28, 2020 4:06 am

Image Reflecting the International Space Station

Explanation: Still bathed in sunlight, the International Space Station arced through the evening sky over lake Wulfsahl-Gusborn in northern Germany, just after sunset on March 25. The familiar constellation of Orion can be seen left of the trail of the orbital station's bright passage. On the right, Venus is the brilliant evening star above the western horizon. With the camera fixed to a tripod, this scene was captured in a series of five exposures. How can you tell? The short time delay between the end of one exposure and the beginning of the next leaves small gaps in the ISS light trail. Look closely and you'll also see that the sky that appears to be above the horizon is actually a reflection though. The final image has been vertically inverted and the night skyscape recorded in the mirror-like waters of the small lake.

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Ann » Thu May 28, 2020 5:12 am

APOD Robot wrote:

Look closely and you'll also see that the sky that appears to be above the horizon is actually a reflection though. The final image has been vertically inverted and the night skyscape recorded in the mirror-like waters of the small lake.
That's absolutely amazing! :shock: Yes, the branches of the trees are more sharply defined "below" the horizon than above it. So the "sky" is just a reflection in water.

Fantastic! :D

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by GeoXXXXX » Thu May 28, 2020 9:43 am

I actually prefer the image with the orientation as taken because it looks like it’s daylight and somehow you are looking down into where it’s night. Chilling actually!
Reminds me of an Alan Parsons Project song...
“ Like a mirror held before me
Large as the sky is wide
And the image is reflected
Back to the other side”


Eric

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by heehaw » Thu May 28, 2020 10:10 am

The reflected station continues through gaps in the text below!

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by orin stepanek » Thu May 28, 2020 11:26 am

Something's amiss; why is there more clarity in the reflection?
And why would the clouds be only in the reflection? Anyway
not mentioned is the Pleiades near Venus! 8-)
ISS-Lighttrail-Reflection_invert.jpg
I take it all back; not clouds but something in the water! :oops:
ISS-Lighttrail-Reflection_invert.jpg
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Re: APOD: Reflecting the ISS (2020 May 28)

Post by De58te » Thu May 28, 2020 12:21 pm

Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this concept of reflection really thought out and interesting.

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by orin stepanek » Thu May 28, 2020 12:41 pm

De58te wrote:
Thu May 28, 2020 12:21 pm
Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this concept of reflection really thought out and interesting.
It is indeed a very interesting picture! Very beautiful catch! :D
Orin

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Chris Peterson » Thu May 28, 2020 1:37 pm

De58te wrote:
Thu May 28, 2020 12:21 pm
Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this concept of reflection really thought out and interesting.
The amount of light that is reflected off a still water surface depends on the angle of incidence. Taking that to be about 45° here, and solving the Fresnel equation, puts the reflected intensity at about 5%. Photographically, that means there is more than a 4-stop difference between the intensity of the sky and its reflection.
Chris

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by TheZuke! » Thu May 28, 2020 1:48 pm

Did the ISS eclipse Aldabaran?
In other words;
Where is that big red star that is usually inline between Orion's belt and the 7 sisters?

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Chris Peterson » Thu May 28, 2020 2:00 pm

TheZuke! wrote:
Thu May 28, 2020 1:48 pm
Did the ISS eclipse Aldabaran?
In other words;
Where is that big red star that is usually inline between Orion's belt and the 7 sisters?
It's close, but I don't think the ISS path is occulting Aldebaran. It's just MIA.
Chris

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by johnnydeep » Thu May 28, 2020 2:21 pm

Chris Peterson wrote:
Thu May 28, 2020 1:37 pm
De58te wrote:
Thu May 28, 2020 12:21 pm
Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this concept of reflection really thought out and interesting.
The amount of light that is reflected off a still water surface depends on the angle of incidence. Taking that to be about 45° here, and solving the Fresnel equation, puts the reflected intensity at about 5%. Photographically, that means there is more than a 4-stop difference between the intensity of the sky and its reflection.
Why is that bright red light near the center in the real sky below not in the reflection above?
"To Boldly Go......Beyond The Fields We Know."

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Chris Peterson » Thu May 28, 2020 2:28 pm

johnnydeep wrote:
Thu May 28, 2020 2:21 pm
Chris Peterson wrote:
Thu May 28, 2020 1:37 pm
De58te wrote:
Thu May 28, 2020 12:21 pm
Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this concept of reflection really thought out and interesting.
The amount of light that is reflected off a still water surface depends on the angle of incidence. Taking that to be about 45° here, and solving the Fresnel equation, puts the reflected intensity at about 5%. Photographically, that means there is more than a 4-stop difference between the intensity of the sky and its reflection.
Why is that bright red light near the center in the real sky below not in the reflection above?
The light path in that direction is probably blocked by the ridge or by vegetation.
Chris

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by TheZuke! » Thu May 28, 2020 3:09 pm

johnnydeep wrote:
Thu May 28, 2020 2:21 pm
Why is that bright red light near the center in the real sky below not in the reflection above?
Ah! You've found Aldebaran!
:D

heehaw

Re: APOD: Reflecting the ISS (2020 May 28)

Post by heehaw » Thu May 28, 2020 3:20 pm

heehaw wrote:
Thu May 28, 2020 10:10 am
The reflected station continues through gaps in the text below!
Man, am I dumb! When I resized the window, of course the text is displaced! I still kind of enjoyed it when I saw it, though!

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Chris Peterson » Thu May 28, 2020 3:24 pm

heehaw wrote:
Thu May 28, 2020 10:10 am
The reflected station continues through gaps in the text below!
No, it doesn't. The full image is seen on the main page. It's just shown upside down. When you click through to the actual source image, it's shown correctly. The entire ISS pass is caught in the reflection. Only part of it is caught in the sky.
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Re: APOD: Reflecting the ISS (2020 May 28)

Post by Tularosakid » Thu May 28, 2020 7:52 pm

I'm wondering if part of the difference in the direct vs reflected part of the image is due to the polarization filtering of light reflected off water.

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Re: APOD: Reflecting the ISS (2020 May 28)

Post by johnnydeep » Thu May 28, 2020 7:53 pm

Chris Peterson wrote:
Thu May 28, 2020 2:28 pm
johnnydeep wrote:
Thu May 28, 2020 2:21 pm
Chris Peterson wrote:
Thu May 28, 2020 1:37 pm


The amount of light that is reflected off a still water surface depends on the angle of incidence. Taking that to be about 45° here, and solving the Fresnel equation, puts the reflected intensity at about 5%. Photographically, that means there is more than a 4-stop difference between the intensity of the sky and its reflection.
Why is that bright red light near the center in the real sky below not in the reflection above?
The light path in that direction is probably blocked by the ridge or by vegetation.
Ah. And now that I look, ALL the tree trunks have their bottom millimeter or two missing from the reflection, so perhaps the land rises up slightly to cut off the reflection.
"To Boldly Go......Beyond The Fields We Know."