Our Beautiful Universe - Photos and Videos

In summary: I love it and the clip finishes with a great quote:In summary, these threads are all about the beauty and awesomeness of our Universe. If you feel like it, please share video clips and photos (or nice animations) of space and objects in space in this thread. Your posts, clips and photos may by all means include scientific information; that does not make it less beautiful to me (n.b. the posts must of course comply with the PF guidelines, i.e. regarding science, only mainstream science is allowed, fringe/pseudoscience is not allowed).
  • #1,541
Thor’s Helmet nebula (NGC 2359) in the constellation Canis Major, taken from my back patio. The emission nebula is approximately 12,000 light years away, and about 30 light years across. Total integration time: 27.83 hours, in Hubble palette narrowband.

ThorsHelmetFinal_800x612_forPF.jpg


Vikings did not wear horns or wings on their helmets -- well, not the practical helmets anyway. It’s possible, albeit uncertain, that there may have been winged or horned helmets used for ritualistic purposes in Viking age Scandinavia. The Oseberg Tapestry (dated to about 834AD) is a rare example that may depict a procession leader wearing what looks like a helmet with wings or horns; however, it’s difficult to interpret.

What is known from Viking mythology is that Thor had a piece of whetstone (sharpening stone) lodged in his skull. I’ll briefly, very briefly, summarize this story from Skáldskaparmál in the Prose Edda.

Odin met a giant named Hrungnir, who was made mostly (or at least partially) of stone. A spontaneous horse race ensued between the two on their horses from the land of giants to Asgard. Odin and his horse Sleipnir arrived at the gates of Asgard first. The gods invited Hrungnir into Val-hall for a drink. Apparently, there’s lots of drinking to do in Val-hall. Drinking, it seems, is a big part of what those in Asgard do. And while there, Hrungnir drank a lot. Like a whole lot. Then he became quite belligerent.

Before I continue, this is really starting to remind me of an escapade I had myself, many, many years ago. One afternoon I took a break from my studies and went to the neighborhood pub for a late lunch. There was a horse race playing on the old television in the corner. An acquaintance ordered some shots. Another friend ordered a round of ale. And when it was my turn, I ordered both. Apparently, there was a lot of drinking to be done in the pub. Drinking, it seems, is a big part of what people in the bar do.

Equipment:
10” Meade LX200-ACF on a equatorial wedge
Optec Lepus 0.62 focal reducer
Astronomik narrowband filters (SII, Ha, Oiii)
ZWO ASI1600MM-COOL monochrome camera

Hrungnir started mouthing off, boasting and bragging, and mostly being very unpleasant. Freya kept serving him drinks and the rest of the gods at the table tolerated his outbursts because the gods are quite hospitable. This continued for some time. But when rude brags and boasts turned to threats, the gods called Thor into the hall. Thor had had enough and escorted him out of Val-hall. Enraged, Hrungnir challenged Thor to a duel as soon as Hrungnir could return with a giant whetstone, his favorite weapon, and his shield. Thor gladly accepted.

In my case, I didn’t make any boasts or threats, but after all the yelling and singing and dancing on the tables (my hip was OK back then), the bar staff made it pretty clear that I had overstayed my welcome.

Software:
Nighttime Imaging ‘N’ Astronomy (N.I.N.A.)
PixInsight
Topaz Labs Denoise AI

At the duel, Thor threw his hammer, Mjölnir, at Hrungnir, and Hrungnir threw his whetstone at Thor. The two weapons met in mid-air with the whetstone shattering followed by Hrungnir’s head shattering by Mjölnir. Part of the whetstone hit the ground (from which all other whetstone’s come) and another shard of the whetstone lodged in Thor’s skull.

In my adventure, I didn’t battle a stone giant, but I did stub my toe and tripped, falling on the hard concrete of the sidewalk. There may have been a few small bits of gravel stuck in my scalp.

Integration:
SII: 7.8 hours
Ha: 8.08 hours
Oiii: 11.95 hours
Total: 27.83 hours

In an effort to remove the whetstone, Thor sought out a sorceress called Groa, wife of Aurvandil the Bold. Thor had recently carried Aurvandil back from the land of the giants in a basket. It was very cold and Aurvandil’s toe had frozen off. Thor took Aurvandil's toe and threw it up into the heavens, where it became a star. Later, when Groa started her spells to remove the whetstone, Thor told her about meeting her husband, Aurvandil, and that he would be home soon. Groa was so overjoyed that her husband would be returning that she forgot all her spells. And thus, the whetstone in Thor’s skull would forever remain.

In my case, on my walk home, I was certainly in no condition to throw anything “up into the heavens,” but I did throw up right then and there.

Sources:
EDDA, Snorri Sturluson, translated by Anthony Faulkes, Published by Everyman 1987, Reissued 1992, 1995, pp. 77-80.
My personal story is unworthy to source.
 
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Astronomy news on Phys.org
  • #1,542
best rendering i’ve seen of a planetary collision…

 
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  • #1,543
Devin-M said:
best rendering i’ve seen of a planetary collision…


Wow. Not much would survive that!
 
  • #1,544
Pleiades and California nebula.
-Sony A7 + Sony 50/1.8 + Sky Watcher Star Adventurer
-120x30s, f/2.8 iso 3200
-Photoshop and PixInsight
plejády kopie (1).jpg
 
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  • #1,545
Crescent moon tonight- hazy high clouds and very poor seeing conditions. 800/5.6 lens, 1/8s, ISO 400 (50% downsampled, original is 1750 x 1750 pixels):

DSC_4640.tiff (RGB)-1.jpg


And again, 1/8s ISO 8000:
DSC_4641.tiff (RGB).jpg
 
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  • #1,546
The Crab Nebula (M1) in the constellation Taurus, imaged from my back patio. The Crab Nebula is about 6,500 light years from Earth, and about 11 light years across. It is a supernova remnant and pulsar wind nebula. Its central star went supernova in the year 1054 (as seen from Earth) and was recorded by Chinese astronomers. What you’re seeing here is the result of the supernova and pulsar winds nearly 1000 years after the massive explosion. Imaged in Hubble pallet narrowband, total integration time: 15.6 hours.

Crab2021_SharpendFinal_SmallForPF.jpg


After weeks of cloudy skies and rain, I was feeling a little crabby. So, when the skies finally cleared, I decided to turn to big crab.

Equipment:
Meade 10” LX200-ACF on an equatorial wedge
Astronomik narrowband filters
ZWO ASI183MM monochrome camera

Software:
Nighttime Imaging ‘N’ Astronomy (N.I.N.A.)
PixInsight
Topaz Labs Denoise AI
Topaz Labs Sharpen AI

Integration:
All images binned 3x3
SII: 85x240sec (5.67 hours)
Ha: 84x240sec (5.60 hours)
Oiii: 65x240sec (4.33 hours)
Total integration time: 15.6 hours

Crab fun-facts:

The Crab Nebula (M1) is the first item in the Messier list [1].

The largest Earth-based crab is the Japanese Spider Crab, who’s body can grow up to 16 inches (40 cm) and who’s legs can grow up to 12.1 feet apart (3.7 m) [2]. You might think 12.1 feet is long for a crab, but that’s just peanuts compared to the Crab Nebula (M1).

There's a running joke among evolutionary biologists that given enough time, every (crustaceous) species will eventually become crab shaped [3].

"Crab people. Crab people. Taste like crab, talk like people.” [4]

The Chicago Bulls (basketball team) logo, when turned upside down, looks like a robot having intercourse with a crab [5].
EEcgzpiXsAIjKA0?format=jpg&name=360x360.jpg
EEcgzpjXoAAYZRt?format=jpg&name=360x360.jpg

I suspect – without evidence – that this is a subtle tribute to the Crab Nebula (M1) in the constellation Taurus, the bull. And robots. Sweet, sweet, crab lovin’ robots.

It would probably make sense to move the Crab Nebula (M1) from the constellation Taurus to Cancer, but that would take a lot of effort.

Sea stars and sea crabs can be antagonistic, fighting over coral [6]. Space stars and space crabs might seem antagonistic, with the supernova explosion, pulsar winds, and all, but that's just for show.

Crabs make you do your laundry [7].

Sources:
[1] https://en.wikipedia.org/wiki/Messier_object
[2] https://en.wikipedia.org/wiki/Japanese_spider_crab
[3] https://www.popsci.com/story/animals/why-everything-becomes-crab-meme-carcinization/
[4] https://southpark.fandom.com/wiki/Crab_People
[5] https://mashable.com/article/chicago-bulls-robot-sex-with-crab-logo
[6] https://peerj.com/articles/574/
[7] https://www.cdc.gov/parasites/lice/pubic/treatment.html
 
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  • #1,547
"Houston, I had no problem!"
- a 400 mm tele lens and 2x teleconverter versus the Moon

I found an old M42 teleconverter (which doubles the focal length) which I won on an online auction for a very good price. The brand is "Expert" (the company Expert was founded by a Swede) but I think it was made by a Japanese third-party producer (there's a "Made In Japan" text on it).

Here's the teleconverter:
Expert Teleconverter.jpg


I've read online that the quality of teleconverters can vary greatly, and also read that some complain
about diminishing image quality when using one. Therefore my expectations was moderate, but I was
pleasantly surprised by the result I got when I took it out for test run on the Moon.

According to Stellarium, this is what a 400mm tele lens and a 2x teleconverter (i.e. a focal length of totally 800mm) would look like (the red frame is what the sensor would capture):

Stellarium Screenshot.jpg


And sure enough, that is pretty much what it looked like. Here one frame of the original photo sequence:

Moon Sample Shot.jpg

(it looks a bit dim to my eyes, so I'll probably use a higher ISO next time)And here's the final image after stacking (25% of the best of totally 200 photos, grayscale):

51813081847_edb1b29419_k.jpg


Pretty nice detail, and I was quite pleased. :smile:

Since there was much detail, I digitally magnified a part in the northern hemisphere, and identified some features and places (with the help of the page Moon mountains observing guide (space.com)):

Moon mountains observing guide (space.com) said:
Two major mountain ranges divide two other features of the lunar landscape.The Mare Serenitatis ("Sea of Serenity") is separated from the Mare Imbrium ("Sea of Showers") by the Montes Caucasus to the north and the Montes Apenninus to the south. Where these two meet is the prominent mountain Mons Hadley, named for British optician and instrument maker John Hadley (1682–1743). Apollo 15 landed here in July 1971.
(my coloring to match my magnified image below)

Moon Details 1b.jpg

(here's a link to the Apollo 15 landing site on Google Moon (the landing site is in the center of that map))

And here's another stacked photo from my session in color:

51814764255_a324050a93_k.jpg


And here's the gear (with an attached intervalometer):

Utrustning.jpg


Gear: Sony A6000, Tokina 400mm f/6.3, Expert 2x teleconverter
Settings: f/8, 1/1000s exposure, ISO 800
Processing: 200 photos taken, 25% of the best stacked with AutoStakkert
Software used: PIPP, AutoStakkert and postprocessing in Photoshop
 
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  • #1,548
Have you tried this with a green filter?
 
  • #1,549
chemisttree said:
Have you tried this with a green filter?
No, I haven't got one for this setup. But thanks for the reminder! :smile:
I have heard about green filters for the Moon, but I had forgotten about it.
Do you think it would improve the imaging?
 
  • #1,550
No way to tell but if the optics have been corrected to a particular color, green is usually it. Fraunhofer doublets are usually corrected that way. Not sure about the lens and focal doubler you are using.

Does the lens exhibit any chromatic abberation in daylight photos?
 
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  • #1,551
DennisN said:
I have heard about green filters for the Moon
Oh, I thought @chemisttree was making a cheesy joke.
 
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  • #1,552
If the atmosphere is unsteady, sometimes a red filter is best. The old moon filters usually had a deep green tint.

1642001841818.jpeg
 
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  • #1,553
chemisttree said:
Does the lens exhibit any chromatic abberation in daylight photos?
I will test it and check. :smile:
 
  • #1,554
A break in the clouds last night- first time in what seems like ∞ weeks. Cigar (M82) and Bode's (M81) galaxies @ 800/5.6, 9300 s integration time, 20s subs:

1_11_22-mod-lpc-cbg-mod-St-9300s copy.jpg


This was, by far, the worst imaging conditions I have ever dealt with- the temp was about 15°F and with the strong, gusting wind chill, about 5°F. Very poor transparency and seeing conditions. And the wind knocking my setup about. Normally, I wouldn't bother on a night like that, but as I said it has been about ∞ weeks since I could see stars at night. So... yeah.
 
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  • #1,555
Last night was very clear, excellent transparency, but also very poor seeing. Rather than fighting a losing battle re: PSF FWHM, I used my 105mm lens; smaller aperture = less susceptibility to seeing conditions. Here's Orion @ 105/2, 8.5 hrs Total exposure using 30s subs:

105mm_Orion-St-19380s copy.jpg


At 1:1, the Flame and Horsehead nebulae:

105mm_Orion-St-30450s.tiff (RGB)-2.jpg


Stopping down the lens gives those nice starburst diffraction patterns... off-axis, though, the lens performance starts to degrade (faster than I expect), it's most noticeable as a greenish tint around Rigel. Here's the Orion Nebula, the lens performance is not as good as I would like...

105mm_Orion-St-30450s.tiff (RGB)-3.jpg


Barnard's loop and other molecular cloud features are mostly too faint (unfortunately- I was motivated by this image), but M78 and NGC 2112 look ok:

105mm_Orion-St-30450s.tiff (RGB)-4.jpg


There's a lot I like about the lens (Nikkor 105/1.4), I think the problem is a slight angular misalignment between the image and sensor planes and I'm not sure if this is 'within spec' or not; not sure how to compensate either way- it's not a 'micro focus' adjustment.
 
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  • #1,556
In memoriam/in memory of

I am going to tell a story I haven't told here before. This thread has been going for 7 years now.
There is a reason I started this thread, "Our Beautiful Universe", way back on March 1, 2015.

Believe it or not, I did not start this thread because I like astronomy. I do like astronomy.
But the reason I started the thread was because of something completely different.

On February 22 2015, I had to put one of my dear cats to sleep.
Long story short, it was very painful because it was the first time I had to do such a thing,
and I had to do it the very same day I took him to the vet (he had lethal kidney values).

I felt terrible. Even though I don't know how it feels to amputate anything, it felt like I had been amputated.

One week later I was still grieving, and felt I had to get my mind on something else.
I watched a couple of inspiring videos about the universe and the conditions for life, and shortly after that I started this thread as a celebration of our Universe, life and existence.

Now, 7 years later, this thread has 1,555 posts from countless of PF members, and the thread has been viewed 134'000+ times. We have shared countless of fascinating videos, photos and advice of various things related to astrophotography. And I'm not sure I would have started doing some astrophotography myself if it was not for this thread.

And all this because of this little cat who once existed, and his name was Nisse (2006-2015):
Nisse 1.jpg


So when life gives you lemons, make lemonade. :smile:

And since this still is an astro thread and not a cat thread, here's the Cat's Eye Nebula:

1024px-NGC6543.jpg
 
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  • #1,557
Core of Andromeda Galaxy, 2.5Mly
2130mm f/14.2 29x 90sec (43.5min) 6400iso, Bortle 2

CC40F887-5D41-400E-A974-A3112035AA51.jpeg


It’s been a while since I’ve taken any astro-photos (its been cold, cloudy and rainy for quite a long time.) I managed to find a break in the clouds last night while the moon was down and captured this photo of the core of Andromeda Galaxy, which is around 2.5 million light years distant. I shot using a 150mm diameter Meade Maksutov Cassegrain on a Star Adventurer 2i mount with some modifications to go probably 3x over the weight limit with a Nikon D800 camera body. I aimed the telescope by taking test shots and plate solving through a website on my phone and then making adjustments. I used the 29 best images although I think I got around 60 total, only about half had round enough stars with 90 second exposures at this focal length on this mount. My bortle 2 dark sky location is near Shingletown, California.

DCF0D85F-4BA6-4829-996F-B37A831B5901.jpeg

9E4447A6-2DB9-4CF4-BA61-96371BF5FF2E.jpeg
 
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  • #1,558
Quick question... Sometimes I shoot dark calibration frames to remove noise from the final image on the way home (for example I might take 10x shots of 5min each at 6400iso with the lens cap on). Because I'm too impatient to wait around at the cold, dark sky location, the camera is heating up from for example 35F (outdoor temp) to 70F in the car while I drive. This results in the amount of noise in each dark frame increasing as the temperature of the camera increases, as seen in the animation below. My conceptual understanding is the photodiodes in the CMOS sensor are operating much like solar panels, and are somewhat sensitive to infrared light while taking exposures even when the lens cap is on. My question is can solar cells or CMOS sensors convert infrared light into electricity, and if so how does that reconcile with the 2nd Law of Thermodynamics? For example, I thought I shouldn't be able to extract useful work from a single temperature reservoir... but if a solar panel can convert infrared light into electricity, isn't it extracting work from a single temperature reservoir (suppose it's immersed in an insulated tank of water as a heat source)?

https://www.speakev.com/attachments/13c208ea-b300-4a24-a496-9e9f9fae4c25-gif.156383/
 
  • #1,559
Devin-M said:
Sometimes I shoot dark calibration frames to remove noise from the final image on the way home (for example I might take 10x shots of 5min each at 6400iso with the lens cap on). Because I'm too impatient to wait around at the cold, dark sky location, the camera is heating up from for example 35F (outdoor temp) to 70F in the car while I drive.
You will almost certainly get better results by shooting your darks in concert with your lights. Shoot a couple of light frames, then shoot a dark, then a few more lights, then a dark. Rinse and repeat. The better the temperature match, the better the dark frame subtraction.

Devin-M said:
My conceptual understanding is the photodiodes in the CMOS sensor are operating much like solar panels, and are somewhat sensitive to infrared light while taking exposures even when the lens cap is on.
My understanding is that it's the thermal motion of the electrons in the sensor that leads to the generation of dark current, not IR radiation. A single IR photon doesn't have enough energy to cause an electron to jump the energy gap, but a lucky collision/interaction between several electrons/ions can give an electron enough energy to jump the gap and into the area of the pixel well that stores the photoelectrons prior to readout.
Devin-M said:
My question is can solar cells or CMOS sensors convert infrared light into electricity, and if so how does that reconcile with the 2nd Law of Thermodynamics? For example, I thought I shouldn't be able to extract useful work from a single temperature reservoir... but if a solar panel can convert infrared light into electricity, isn't it extracting work from a single temperature reservoir (suppose it's immersed in an insulated tank of water as a heat source)?
No. Prior to exposure the pixel wells undergo a charge separation process that puts them in a high-energy state. Photons, or random interactions from thermal motion, cause electrons to jump an energy gap and get caught in this charged well. Given enough time or photons the well becomes completely saturated and can no longer collect charge. You won't extract more energy out of this than it took to separate the charges in the first place.

A solar panel operates somewhat differently and I don't really know enough to explain it well. However, I do believe that the solar panel needs to be at a lower temperature than the emitting object it is capturing radiation from. Besides, the solar panel itself and the surrounding environment is a temperature reservoir, so there's more than one.
 
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  • #1,560
Devin-M said:
Quick question... Sometimes I shoot dark calibration frames to remove noise from the final image on the way home (for example I might take 10x shots of 5min each at 6400iso with the lens cap on). Because I'm too impatient to wait around at the cold, dark sky location, the camera is heating up from for example 35F (outdoor temp) to 70F in the car while I drive. This results in the amount of noise in each dark frame increasing as the temperature of the camera increases, as seen in the animation below.

An alternative that you might want to try in your off time (i.e., a cloudy night), is to realize that you can reuse DARK frames (for the given camera). Take your camera and an accurate thermometer outside and let the camera the acclimate to the outside temperature. Once the camera is in thermal equilibrium, start taking DARKs. Lots of DARKs.

Vary the exposure times in a controlled, roughly exponential way -- exposure times that you might likely use for your LIGHT frames. For example, 40 sec, 60 sec, 90 sec, 120 sec, 180 sec, 240 sec, 300 sec, etc.

The whole while, keep meticulous records of the ambient temperature. Also keep a record of the camera's ISO setting you are using for each dark (only use ISO settings that you would use for LIGHT frames). Sit down, have a beer in the cold. This will take a while. Maybe have two beers. Repeat as much as you can. As the night continues, the temperature is likely to drop, so you should expect to have several different temperature points for your DARK frames.

Later, organize these DARK frames. Rename each DARK frame such that it has
  • Specific camera taking the photos
  • ISO setting,
  • Exposure time,
  • Temperature for that particular dark frame, and
  • Some unique identifier so you don't accidentally overwrite existing DARK frames
in the file name.

Repeat the next cloudy night. Put the camera in the refrigerator and repeat there too. If you live in a cold climate, and foresee yourself taking astrophotos in really cold weather, try the freezer as well.

Eventually, you'll have a DARK library with many frames for each particular ISO setting + Exposure time + temperature. Ideally, you'll have many DARK frames for each combination. Organize these on your comptuer. Once you have that, all you need to do when taking LIGHT frames is to record the temperature at the time (stash your thermometer in your camera bag), and your corresponding DARK frames will be waiting for you at home.

(Of course, the data is specific to the specific camera. You cannot share DARK frames between cameras.)

---------------

For personal reference, I have a few cooled cameras (dedicated, astrophotography cameras). Having a temperature controlled camera makes the process a lot easier. But even then it still takes a while. Whenever I get a new cooled camera, the first thing I do set the camera next to the computer and let it take DARKs for days. Literally days. But once it's done I don't have to take DARKs again for maybe a year or two. And I only use 2 temperature settings (0 deg C and -5 deg C).
 
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  • #1,561
Drakkith said:
My understanding is that it's the thermal motion of the electrons in the sensor that leads to the generation of dark current, not IR radiation. A single IR photon doesn't have enough energy to cause an electron to jump the energy gap, but a lucky collision/interaction between several electrons/ions can give an electron enough energy to jump the gap and into the area of the pixel well that stores the photoelectrons prior to readout.

No. Prior to exposure the pixel wells undergo a charge separation process that puts them in a high-energy state. Photons, or random interactions from thermal motion, cause electrons to jump an energy gap and get caught in this charged well. Given enough time or photons the well becomes completely saturated and can no longer collect charge. You won't extract more energy out of this than it took to separate the charges in the first place.

A solar panel operates somewhat differently and I don't really know enough to explain it well. However, I do believe that the solar panel needs to be at a lower temperature than the emitting object it is capturing radiation from. Besides, the solar panel itself and the surrounding environment is a temperature reservoir, so there's more than one.
Could you comment on the graph on this webpage… I might be misinterpreting it but I believe graph (a) shows a particular detector which is at 300k (~80F) operating temperature generating current from mid-infrared light up to 4000 nanometers with zero bias, which I take to mean the detector is operating in photovoltaic mode with no outside voltage applied…

https://www.researchgate.net/figure/a-g-The-spectral-responsivity-measured-at-zero-bias-ie-photovoltaic-mode-for-the_fig3_346511011
measured-at-zero-bias-ie-photovoltaic-mode-for-the.png

(a)-(g) The spectral responsivity measured at zero bias (i.e. photovoltaic mode) for the Te-hyperdoped Si photodetector at different temperatures. The room-temperature spectral responsivity of a commercial Si-PIN photodiode (model: BPW34) is included as a reference (brown short dot). (h) Illustration of the below-bandgap photoresponse in the Te-hyperdoped Si photodetector. Te dopants introduce deep-level states (intermediate band) inside the Si band gap, which facilitate the absorption of photons with sub-bandgap energies. Process I: VB to CB (Eph ≥ Eg); Process II: VB to IB (Eph ≥ Eg-ETe); Process III: IB to CB (Eph ≥ ETe, only measurable at low temperatures where the thermal contribution is neglected).
 
  • #1,562
Devin-M said:
Could you comment on the graph on this webpage… I might be misinterpreting it but I believe graph (a) shows a particular detector which is at 300k (~80F) operating temperature generating current from mid-infrared light up to 4000 nanometers with zero bias, which I take to mean the detector is operating in photovoltaic mode with no outside voltage applied…
Not really. I'm not an expert in the area of photodetectors and solid state physics and such. I'll try to remember to give it a read tomorrow or the next day if I can, but I might not have time.
 
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  • #1,563
Devin-M said:
Could you comment on the graph on this webpage… I might be misinterpreting it but I believe graph (a) shows a particular detector which is at 300k (~80F) operating temperature generating current from mid-infrared light up to 4000 nanometers with zero bias, which I take to mean the detector is operating in photovoltaic mode with no outside voltage applied…
Quickly skimmed through the article just now. I come to the same conclusion as you.
Note that at 300K an object barely emits any radiation in the 1-5 micrometer range. You have to get warmer for that. You can use the calculator here to see the spectrum emitted by an object at a given temperature. Use 1 micrometer as the upper limit and 5, 10, or 20 as the lower limit to get a good looking graph of the region of interest.
 
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  • #1,564
Drakkith said:
Quickly skimmed through the article just now. I come to the same conclusion as you.
Note that at 300K an object barely emits any radiation in the 1-5 micrometer range. You have to get warmer for that. You can use the calculator here to see the spectrum emitted by an object at a given temperature. Use 1 micrometer as the upper limit and 5, 10, or 20 as the lower limit to get a good looking graph of the region of interest.

Thanks for the calculator! According to its output, with inputs for the emissivity of water (0.96) at 300k (~80F), ordinary room temperature water is emitting some blackbody infrared radiation from 3-4 micrometers— at wavelengths the “Te-hyperdoped Si photodetector” also @ 300k can generate current from in photovoltaic mode… I must be missing something because why couldn’t I just generate a small amount of electricity by submerging these room temperature photodetectors in room temperature water to harvest the 3-4 micrometer infrared black body radiation photons by photovoltaic means? Wouldn’t that conflict with the 2nd Law of Thermodynamics? I shouldn’t be able to generate any useful work from a single temperature reservoir, was my understanding.
FA2A5939-12FA-4283-BB55-235C43E2499F.png

C025E1ED-3E53-40EE-B943-936E3569BD30.jpeg
 
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  • #1,565
Devin-M said:
I must be missing something because why couldn’t I just generate a small amount of electricity by submerging these room temperature photodetectors in room temperature water to harvest the 3-4 micrometer infrared black body radiation photons by photovoltaic means? Wouldn’t that conflict with the 2nd Law of Thermodynamics? I shouldn’t be able to generate any useful work from a single temperature reservoir, was my understanding.
That I can't answer. I'm certain the 2nd law isn't being violated, but I couldn't tell you how or why it isn't.
 
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Devin-M said:
I must be missing something because why couldn’t I just generate a small amount of electricity by submerging these room temperature photodetectors in room temperature water to harvest the 3-4 micrometer infrared black body radiation photons by photovoltaic means?

Maybe I'm missing something myself. But It's my understanding that you couldn't generate any electricity by simply submerging the photodetector in water because there wouldn't be a light source in that situation.

ured-at-zero-bias-ie-photovoltaic-mode-for-the-png.png


It's my understanding of the test setup that the photodetector is placed and held at a given temperature, then it is exposed to a light source of a specific wavelength and specific intensity (with a proportional power reaching the detector, measured in Watts) and the current of the photodetector is measured (measured in milliamps). That is used to generate a single point on a single graph. For any given situation (wavelength of the light source and temperature of the photodetector), the current of the photodetector is proportional to the power of the light source. Which is why the measurements are in units of mA/W.

At least that's my understanding. The power is ultimately coming from the light source. The 2nd Law is not violated. The current vanishes as soon as you turn off the light.
 
  • #1,567
collinsmark said:
Maybe I'm missing something myself. But It's my understanding that you couldn't generate any electricity by simply submerging the photodetector in water because there wouldn't be a light source in that situation.

View attachment 296237

It's my understanding of the test setup that the photodetector is placed and held at a given temperature, then it is exposed to a light source of a specific wavelength and specific intensity (with a proportional power reaching the detector, measured in Watts) and the current of the photodetector is measured (measured in milliamps). That is used to generate a single point on a single graph. For any given situation (wavelength of the light source and temperature of the photodetector), the current of the photodetector is proportional to the power of the light source. Which is why the measurements are in units of mA/W.

At least that's my understanding. The power is ultimately coming from the light source. The 2nd Law is not violated. The current vanishes as soon as you turn off the light.
A 300k (80F) black body emits some infrared between 3 & 4 micrometers, which is in the detection range of the photodetector.

fa2a5939-12fa-4283-bb55-235c43e2499f-png.png
 
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Devin-M said:
Wouldn’t that conflict with the 2nd Law of Thermodynamics? I shouldn’t be able to generate any useful work from a single temperature reservoir, was my understanding.
Should some of this side-discussion be split off into the Thermodynamics forum?
 
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Devin-M said:
A 300k (80F) black body emits some infrared between 3 & 4 micrometers, which is in the detection range of the photodetector.

View attachment 296248
Yes, but the photodetector is also emitting infrared too -- the same amount that it receives when its own temperature is at 300 K, along with everything else in the surroundings being at 300 K, and when no external light source is present. Without the presence of the external light source the net current is zero. At least that's my understanding.

I don't know the test setup, but here's how I imagine it:

A broadband blackbody radiation source is involved; an incandescent bulb will do. The light from the source passes through a slit followed by a diffraction grating, thus splitting up the light (including infrared light) into a spectrum. The intensity along the spectrum is measured and calibrated (perhaps with a small, calorimeter device). With this information, the light intensity along specific wavelengths of the spectrum is known.

The photodetector can then be placed along the spectrum for measurements. Changing the wavelength is just a matter of moving the photodetector spacially to a different part of the spectrum produced by the light source + diffraction grating.

But again, if I'm imagining the setup correctly, the current in the photodetector will vanish when the light source is turned off.

**** Edit *****
Reading into the research paper a little more (https://www.researchgate.net/publication/346511011_Silicon-Based_Intermediate-Band_Infrared_Photodetector_Realized_by_Te_Hyperdoping), it states in the Device Measurement seciton: "A Globar (SiC) source coupled with a TMc300 Bentham monochromator equipped with gratings in Czerny-Turner reflection configuration was used as the infrared monochromatic source. Its intensity is spatially homogenized and was calibrated with a Bentham pyrometric detector."

The "TMc300 Bentham monochromator" utilizes a diffraction grating turret. So my imagined setup, albeit a bit simplistic, was conceptually accurate.
****************

berkeman said:
Should some of this side-discussion be split off into the Thermodynamics forum?
That sounds like a good idea to me.
 
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collinsmark said:
That sounds like a good idea to me.
Can you folks suggest which posts I should split off into the Thermo forum? I don't want to mess up the astrophotography part of the discussion.
 
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What if we just post further comments in a new discussion?
 
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That would be good too. I'm only able to move posts, not copy/paste posts. So maybe start a new discussion in the Thermo forum based on the discussion here. It's a pretty interesting discussion, IMO.
 
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berkeman said:
Can you folks suggest which posts I should split off into the Thermo forum? I don't want to mess up the astrophotography part of the discussion.
Devin-M said:
What if we just post further comments in a new discussion?
berkeman said:
That would be good too. I'm only able to move posts, not copy/paste posts. So maybe start a new discussion in the Thermo forum based on the discussion here. It's a pretty interesting discussion, IMO.

I would suggest, if @Devin-M agrees, for @Devin-M to create a new thread in the appropriate forum (Thermodynamics?) with basically a copy-and-paste copy of Post #1558 as the original post.

Then copy over posts #1561 - Onward, to the new thread. The other posts are good for the astrophotography thread.

Post #1559 by @Drakkith is a toughy though; that post could go either way.
 
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DA6E734C-3546-44B5-A0A1-15B33190235E.jpeg


My most recent astro-photo-session was a terrible failure. Long story short I spent hours in the cold & this was the only remotely salvageable shot from the whole session and it was done with my iphone. I call it “Tree with iPhone in Bortle 2 conditions.” I was attempting to shoot a dim target at 2130mm focal length at the limit of exposure time (90 sec per subframe) I can do without too much tracking issues and also at the limit of iso sensitivity I can reasonable achieve (6400iso). Unfortunately that wasn’t enough exposure time so while the stars came out ok there was no nebula visible in the final photos. I thought I’d be able to bring it out in post processing but it was just a bunch of noise. I’m going to have to choose a brighter target, switch to a much shorter focal length with bigger aperture, or shell out thousands of $… for now I’m ruling out the 3rd option.

Edit: I was too embarrassed to show the final image taken through the telescope but here it is, for posterity:

DSC_0508-Mean-2.jpg


Here are a couple more photos of the same region through a much more capable scope of NGC 2170:

sy5Uy6h9zBf-_1824x0_iS40atce.jpg


Source:
https://www.astrobin.com/2nzzzj/0/

N2170s.jpg


Source:
https://en.wikipedia.org/wiki/NGC_2170
 
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