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spaceguy
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14 Jan 2017 12:51

DoctorOfSpace wrote:
If you saw an real accretion disk you wouldn't be able to see those effects anyway.  Accretion disks would be brighter than the sun.

I wonder how it would look with a very large, thick accretion disk. But yeah, reality over presentation, and thus reality demands dis. Would be cool to observe with low exposure too...

EDIT: Different rotation rate throughout the accretion disk is also absent. 
 
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DoctorOfSpace
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14 Jan 2017 12:58

Watsisname explains it pretty well
Watsisname wrote:
When reality looks wrong, change reality? ;)

The temperature of an accretion disk with respect to radius generally follows [math]

Which as a plot, looks like this:
Image

If the disk is hot enough that it emits x-rays (wavelengths between 10-8 and 10-11 meters), then the peak temperature must be hundreds of thousands to millions of Kelvin.

Suppose as in the screenshot that the peak temperature of the disk near the white dwarf surface (about 10,000km out) is about 5 million Kelvin.  Then at twice that radius, the temperature is still about 3 million K.  At 10 times that radius it's about 900,000K.  At 100 times that radius? 150,000K.  You get the picture.  Even at large distances it's still so hot as to be glowing in ultraviolet!  And since luminosity follows temperature to the fourth power, that's a huge luminosity even compared to a typical star, and it would be absolutely blinding.

How far out would we have to extend the disc such that the temperature is merely 5000K and thus peaking in visible light?  That would be ten thousand times the white dwarf's radius!  That's 100 million kilometers -- greater than the distance from the white dwarf to the star it's accreting from!

So that's reality.  White dwarf accretion disks are stupidly bright all the way out!  Trying to extend the disk so that the outer edge isn't stupidly bright would result in a disk that is stupidly unrealistically big.  The only reasonable correction to make it "look right" would be a massive exposure compensation, where everything else including nearby stars are black, as is shown in An'shur's screenshots.
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spaceguy
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14 Jan 2017 13:05

DoctorOfSpace wrote:
Watsisname explains it pretty well
Watsisname wrote:
When reality looks wrong, change reality? ;)

The temperature of an accretion disk with respect to radius generally follows [math]

Which as a plot, looks like this:
Image

If the disk is hot enough that it emits x-rays (wavelengths between 10-8 and 10-11 meters), then the peak temperature must be hundreds of thousands to millions of Kelvin.

Suppose as in the screenshot that the peak temperature of the disk near the white dwarf surface (about 10,000km out) is about 5 million Kelvin.  Then at twice that radius, the temperature is still about 3 million K.  At 10 times that radius it's about 900,000K.  At 100 times that radius? 150,000K.  You get the picture.  Even at large distances it's still so hot as to be glowing in ultraviolet!  And since luminosity follows temperature to the fourth power, that's a huge luminosity even compared to a typical star, and it would be absolutely blinding.

How far out would we have to extend the disc such that the temperature is merely 5000K and thus peaking in visible light?  That would be ten thousand times the white dwarf's radius!  That's 100 million kilometers -- greater than the distance from the white dwarf to the star it's accreting from!

So that's reality.  White dwarf accretion disks are stupidly bright all the way out!  Trying to extend the disk so that the outer edge isn't stupidly bright would result in a disk that is stupidly unrealistically big.  The only reasonable correction to make it "look right" would be a massive exposure compensation, where everything else including nearby stars are black, as is shown in An'shur's screenshots.


I wasn't arguing against you. I was talking about the gravitational and Doppler shift on a larger accretion disk.
 
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Heath
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14 Jan 2017 21:21

Mosfet wrote:
Although a completely clickable interface could be maybe useful with certain hardware...

That is what I was hoping for is a bit of a cleaner UI with how you get to planets and stars and so forth on the look up guides and stuff. Not sure what kinda cleaner UI but there will probably be somebody with a fantastic idea.
 
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Watsisname
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15 Jan 2017 04:46

spaceguy wrote:
Source of the post I was talking about the gravitational and Doppler shift on a larger accretion disk.

Yeah, those effects are shown. :)  A lot of people get thrown by that, since intuition would suggest that you should see the color change.  The color does change, but what you actually notice is more of a change in brightness, because it's like changing the effective temperature, and brightness changes with temperature very quickly (goes as the fourth power).  When astronomers talk of observing different sides of the accretion disk around Sagittarius A* with the EHT, they actually say "Doppler-boosted" or "de-boosted" instead of "blueshift / redshift", because this is such an important effect.
 
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spaceguy
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15 Jan 2017 05:29

Watsisname wrote:
spaceguy wrote:
Source of the post I was talking about the gravitational and Doppler shift on a larger accretion disk.

Yeah, those effects are shown. :)  A lot of people get thrown by that, since intuition would suggest that you should see the color change.  The color does change, but what you actually notice is more of a change in brightness, because it's like changing the effective temperature, and brightness changes with temperature very quickly (goes as the fourth power).  When astronomers talk of observing different sides of the accretion disk around Sagittarius A* with the EHT, they actually say "Doppler-boosted" or "de-boosted" instead of "blueshift / redshift", because this is such an important effect.

Yeah that's what confused me. But the size of the accretion disk also did too, because it mitigates some of the lopsidedness you'd expect from the shifts.
 
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Mosfet
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15 Jan 2017 06:50

Heath, I'd add that on second thought, my statement that using the mouse is slower is inconsistent, because I took into account an unneeded click. Sleep deprivation is to blame, this time ;)
And... Brace yourself... A "Goto" button has been added to the Solar System browser for the next update.
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Heath
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15 Jan 2017 10:02

Mosfet wrote:
Heath, I'd add that on second thought, my statement that using the mouse is slower is inconsistent, because I took into account an unneeded click. Sleep deprivation is to blame, this time ;)
And... Brace yourself... A "Goto" button has been added to the Solar System browser for the next update.

Woo hoo! Thanks man :D You folks are simply the best ever! Oh and another thing that I forgot to ask if it can be added into the game, would there be a way to find objects a bit better/faster in the "Find Object" or "Star Browser" option on the left as well? Let's say I wanted to find a cataloged item such as a red dwarf. Can there be a way to just type in "Red Dwarf" in a search bar and then say you want to find one in however many light years of your position? Because while the way it is set up now with organizing what you want to find by system main star, object parents sun, etc is kinda nice and ok, I was just maybe hoping there would be a possible way to make it more precise or as general as you want. 
 
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DoctorOfSpace
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15 Jan 2017 12:57

spaceguy wrote:
Source of the post I wasn't arguing against you.

Never meant to imply that you were, simply thought you would find that post by Watsisname interesting as it relates.
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problemecium
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15 Jan 2017 15:44

spaceguy wrote:
The doppler shift of the accretion disk is absent.

Not to sound argumentative but no it isn't. It is, however, much more subtle than you might have expected going in. Keep in mind that Doppler shift isn't going to be obvious until the disk contents are moving close to the speed of light, which is only the case near the middle - and thus it's hard to spot unless you either find a black hole with an abnormally small accretion disk or turn the exposure wayyy down until everything but the center region is blacked out.
Image
There you'll notice that the oncoming side is noticeably brighter; it's also blue-tinted to a degree, but Doppler shift goes hand-in-hand with a significant change in brightness, so the "blue" side tends to wash out to white while the "red" side goes dim and hard to see, particularly when it's already emitting mainly blue light due to its temperature (blue minus red equals black). ;)

EDIT: WOW, I got ninja'd by a whole page thanks to not checking whether I was on the last page or not. Sorry! Hopefully my illustration helped out anyway xP
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Mosfet
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15 Jan 2017 16:03

Heath wrote:
Source of the post Thanks man :D You folks are simply the best ever!

SpaceEngineer simply anticipated your same point of view, it's the only one working here :P
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spaceguy
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15 Jan 2017 16:05

problemecium wrote:
spaceguy wrote:
The doppler shift of the accretion disk is absent.

Not to sound argumentative but no it isn't. It is, however, much more subtle than you might have expected going in. Keep in mind that Doppler shift isn't going to be obvious until the disk contents are moving close to the speed of light, which is only the case near the middle - and thus it's hard to spot unless you either find a black hole with an abnormally small accretion disk or turn the exposure wayyy down until everything but the center region is blacked out.
Image
There you'll notice that the oncoming side is noticeably brighter; it's also blue-tinted to a degree, but Doppler shift goes hand-in-hand with a significant change in brightness, so the "blue" side tends to wash out to white while the "red" side goes dim and hard to see, particularly when it's already emitting mainly blue light due to its temperature (blue minus red equals black). ;)

EDIT: WOW, I got ninja'd by a whole page thanks to not checking whether I was on the last page or not. Sorry! Hopefully my illustration helped out anyway xP

It's alright.

Tbh, I wish this game had more player interactive features and mechanics to get a sense of scale, such as a player character. Although I heard it'd be too hard and tedious for the developer to implement. ;/
 
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DoctorOfSpace
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15 Jan 2017 16:35

Why not just get one of the many astronaut mods?  I can always reupload the Astronauts for 0.9.8.
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11ryanc
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15 Jan 2017 17:01

Placemarks would be nice. I often times come across particular areas of interest on a planet's surface, and it can be a trick to locate those same coordinates a second time.
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Heath
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15 Jan 2017 18:48

Mosfet wrote:
SpaceEngineer simply anticipated your same point of view, it's the only one working here :P

What are you saying that my inputs are the only ones that are good ideas? Lol :P
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