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Old 04-07-2017, 09:56 AM   #11
Ulzgoroth
 
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by vicky_molokh View Post
Hmm. About 50 billion km is about the equivalent of 5×10^13 yards, right? So (-2+(-6×13)) = -80ish.
And Neptune is 50 million yards in diameter. So (2+(6×6)) = 38, bumped to 40 for being round.
Thus a need to offset about 40 worth of penalties using Silhouetting, Plain Sight, Signature, Zoom, Extra Time (and probably more than the 30-minute Extra Time limit normally allowed!) etc.

RAW Extra Time (+5), Silhouette (+24) and Plain Sight (+10) already account for 39. So probably a bit on the overkill side.
You probably should get some penalty for doing astronomical spotting from inside the atmosphere and I'm not sure why you'd expect a Signature bonus. But unless the atmosphere penalty is substantial that would suggest you could spot Neptune with the naked eye.
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Old 04-07-2017, 10:03 AM   #12
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by Humabout View Post
IDHMBWM, but an easy way to test this is see if yiu can detect Neptune with TL5 equipment wiithout it. Running the numbers on that should give you a domain of possible values for the Silhouetted bonus.
The problem with this is that the bonus is for systems use a variety of light spectrums, which includes visual, infrared, and some others.

On which note, the SM for Neptune is +47 (including +2 for being a sphere), the distance is -74. Combine this with plain sight and silhouette modifiers and you get a net of +7 to detect it. Considering that the WISE mission could have detected Neptune-sized objects out to 700 AU, this is perfectly reasonable, especially when you consider that WISE could take advantage of extra time.
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Old 04-07-2017, 10:03 AM   #13
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by Ulzgoroth View Post
You probably should get some penalty for doing astronomical spotting from inside the atmosphere and I'm not sure why you'd expect a Signature bonus. But unless the atmosphere penalty is substantial that would suggest you could spot Neptune with the naked eye.
Because 'dim star' implies that it visibly shines, but dimly, due to reflected light.
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Old 04-07-2017, 10:13 AM   #14
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Because 'dim star' implies that it visibly shines, but dimly, due to reflected light.
It would be literally impossible to see if it didn't. Visibly shining due to reflected light is entire means by which objects that aren't themselves light sources are seen.

Of course, Spaceships spotting rules are actually for objects that are (infrared) light sources, not for spotting objects by reflected light. You really should be modifying Neptune's visibility for the illumination level!
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Old 04-07-2017, 10:48 AM   #15
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

The +24 should really replace the +10 for in plain sight, rather than adding to it.

The standard formula for the apparent magnitude of an asteroid is roughly 15.6 - 5 x log10(diameter in km) + 5 x log10 (distance in AU) + 5 x log10 (distance from sun in AU) - 2.5 x log10(albedo) plus a phase modifier; a white 1 km asteroid at half phase at 1 AU would thus be around magnitude 16.5. If we assume a magnitude 0 star is +0, the vision modifier should be -1.2*magnitude or -20. A 1 km asteroid is SM+18 (assuming a +2 for a spherical object), a white or highly reflective object is another +2, a range of 1 AU is -66, so using basic modifiers we get a difficulty of -44, meaning we need another +24 in there to get it up to the expected value of -20.
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Old 04-07-2017, 10:52 AM   #16
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by Anthony View Post
The +24 should really replace the +10 for in plain sight, rather than adding to it.

The standard formula for the apparent magnitude of an asteroid is roughly 15.6 - 5 x log10(diameter in km) + 5 x log10 (distance in AU) + 5 x log10 (distance from sun in AU) - 2.5 x log10(albedo) plus a phase modifier; a white 1 km asteroid at half phase at 1 AU would thus be around magnitude 16.5. If we assume a magnitude 0 star is +0, the vision modifier should be -1.2*magnitude or -20. A 1 km asteroid is SM+18 (assuming a +2 for a spherical object), a white or highly reflective object is another +2, a range of 1 AU is -66, so using basic modifiers we get a difficulty of -44, meaning we need another +24 in there to get it up to the expected value of -20.
That's handy, but keep in mind that Spaceships doesn't use purely visual systems. In fact, Spaceships p. 44 explicitly states that infrared is used for long range detection.
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Old 04-07-2017, 11:02 AM   #17
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by Nemoricus View Post
That's handy, but keep in mind that Spaceships doesn't use purely visual systems.
This is...surprisingly irrelevant, and certainly not enough to give a +10 modifier. Net IR emissions are typically similar to the white body above, though the IR background is significantly different (stars are relatively dimmer, but there's a lot of background dust).
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Old 04-07-2017, 11:07 AM   #18
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by Ulzgoroth View Post
It would be literally impossible to see if it didn't. Visibly shining due to reflected light is entire means by which objects that aren't themselves light sources are seen.
I said 'shines' specifically to distinguish between the amount of light sent to the eyes this way. Let's not pretend that something confused for a (shining) star is the same as something comparable to a human in the same level of darkness.

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Of course, Spaceships spotting rules are actually for objects that are (infrared) light sources, not for spotting objects by reflected light. You really should be modifying Neptune's visibility for the illumination level!
Some of them. There are bonuses if the target has the equivalent of at least Auxialiary power, but a target with no systems running (e.g. a long-lost derelict) gets a +0 signature.
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Old 04-07-2017, 11:22 AM   #19
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

Note that my above calculation did ignore active power generation. Normal 'natural' IR radiation is about 400W x 10^(SM/3), or 40 kW for a SM+6 spaceship. Based on beam output and RoF, 1 EP at SM+6 is at least 3 MW (improved major batteries fire 1/10s, 30 MJ shots); if we call it 4 MW, which is pretty generous, it's equivalent to a SM of +12, and a more likely figure is +13. Thus, the bonus for actively using 1 EP (normally doesn't happen unless using drives or weapons) is 4 + SM/2.

Now, a 100 ton thrust drive has a minimum power output of 4.5 MW x ISp; ISp is equal to (MPS/tank) * 3200. This results in some fairly ridiculous drive signatures for any interesting drive.
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Old 04-07-2017, 11:24 AM   #20
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Default Re: [Spaceships] The value and realism of +24 if Silhouetted Against Deep Space . . .

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Originally Posted by vicky_molokh View Post
I said 'shines' specifically to distinguish between the amount of light sent to the eyes this way. Let's not pretend that something confused for a (shining) star is the same as something comparable to a human in the same level of darkness.
Actually, I don't think there's any such obvious difference.

You don't tend to have humans being the only light-reflecting objects in an area, but if you do (which in normal lived experience requires careful spotlighting) I think they can look pretty shiny.

Satellites can look like stars, albeit suspiciously mobile ones. It's not because they're extraordinarily shiny, it's because they're well-lit against a dark background.

...Anyway, if you're looking at visual spotting of Neptune you definitely need to give it a penalty for having 900 times less intense light than we get here at Earth orbit. In principle there should be some modifier for reflectiveness (since matte black does work to make things hard to see like this) which might be more favorable for Neptune than for a human. Almost certainly more favorable than for a human in dark clothing.
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Originally Posted by vicky_molokh View Post
Some of them. There are bonuses if the target has the equivalent of at least Auxialiary power, but a target with no systems running (e.g. a long-lost derelict) gets a +0 signature.
Yeah, but it's still not spotting by reflected light. It can't be, there would have to be a parameter for the light level.
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