Starship Asterisk*

zbvhs wrote:It was an awfully crude experiment for 100 million bucks, but then, that's probably all you get for the money these days. Why is nobody talking about a Lunar rover? That's really what you need for problems like these.

robotwisdom wrote:

robotwisdom wrote:How wide was the flash?

Very important question!

As best I can guestimate using Google Earth's Moon map (which appears inverted compared to this APOD image), the round crater below the flash is about ten miles wide, so the flash is one-half to one mile in diameter.

robotwisdom wrote:How wide was the flash?

DavidLeodis wrote:In the explanation to the APOD it states the Centaur rocket hit the lunar surface "at 4:31am UT". Should that be 4:31am PDT (Pacific Daylight Time) not 4:31am UT (Universal Time).

neufer wrote:

Orca wrote:This experiment is also a "nerd test." If, after the first time seeing your remote's LED's in your camera, you say, "Woah, that's cool" and show all your friends, you're officially a nerd. I passed the nerd test with flying colors, not content with simply showing friends but also trying out several remotes and several cameras.

Haven't we already passed the "nerd test" by subscribing to _The Asterisk*_ ?

I object to any further qualifications!

Orca wrote:This experiment is also a "nerd test." If, after the first time seeing your remote's LED's in your camera, you say, "Woah, that's cool" and show all your friends, you're officially a nerd. I passed the nerd test with flying colors, not content with simply showing friends but also trying out several remotes and several cameras.

• Those with telescopes might try flashing their remote's LED into the eyepiece and see how far away you can detect the telescopic signal with your camera. Near IR should penetrate haze better than normal light.

http://www.dpfwiw.com/ir.htm wrote:
<<IR images owe their great clarity to the atmosphere's exceptional transparency in the NIR. Scattering by air molecules is much less efficient at NIR than at most visible wavelengths. As a result, NIR photons take on average a much straighter path from object to CCD.

In visible light , scattering severely limits detail on the more distant portions of the far hillside in this hazy afternoon scene. Removing visible light with a Hoya R72 IR filter takes out much of the detail-scrambling scatter. An impressive amount of detail shines through the haze in the IR image, despite the odd false-color scheme.

Chris Peterson wrote:

Orca wrote:A simple and fun demonstration: take your cell phone camera and your TV remote. Point the remote back toward yourself and the outstretched camera. Push buttons. Your camera will detect the IR signals that your eyes can't see! The remote's IR LED's look like flashing white lights on the screen while remaining black as always to the naked eye.

You are talking about near IR here, not mid- or far IR. A good camera won't be sensitive to this, because it is filtered out before it can reach the sensor. Otherwise, the color balance is messed up. But cellphone cameras are often of poor quality, so this would be a good type to try this experiment with.

The emitter on the remote control is probably putting out IR around 800nm. Your eye actually has some sensitivity here, just really low. But if the remote is a bright one, you may be able to see the IR coming out of it. Hold it close to your eye and look right at the emitter. You might notice a dim red signal. That's the IR output; you see it as red because only the red receptors of your eye are stimulated, and you see it as dim because your sensitivity to such a long wavelength is quite low.

Chris Peterson wrote:

Orca wrote:A simple and fun demonstration: take your cell phone camera and your TV remote. Point the remote back toward yourself and the outstretched camera. Push buttons. Your camera will detect the IR signals that your eyes can't see! The remote's IR LED's look like flashing white lights on the screen while remaining black as always to the naked eye.

You are talking about near IR here, not mid- or far IR. A good camera won't be sensitive to this, because it is filtered out before it can reach the sensor. Otherwise, the color balance is messed up. But cellphone cameras are often of poor quality, so this would be a good type to try this experiment with.

The emitter on the remote control is probably putting out IR around 800nm. Your eye actually has some sensitivity here, just really low. But if the remote is a bright one, you may be able to see the IR coming out of it. Hold it close to your eye and look right at the emitter. You might notice a dim red signal. That's the IR output; you see it as red because only the red receptors of your eye are stimulated, and you see it as dim because your sensitivity to such a long wavelength is quite low.

http://www.washingtonpost.com/wp-dyn/content/graphic/2009/10/12/GR2009101200137.html?sid=ST2009101200138 wrote:
Optical Inventions That Fueled the Information Age
The Washington Post / Monday, October 12, 2009

<<This year's Nobel Prize in physics was shared by Charles K. Kao for his development of low-loss optical fiber
and the team of Willard S. Boyle and George E. Smith, who invented the charge- coupled device.>>

Orca wrote:A simple and fun demonstration: take your cell phone camera and your TV remote. Point the remote back toward yourself and the outstretched camera. Push buttons. Your camera will detect the IR signals that your eyes can't see! The remote's IR LED's look like flashing white lights on the screen while remaining black as always to the naked eye.

neufer wrote:

Chris Peterson wrote:

kovil wrote:Remember, these images are in the infrared, which shows kinetic energy's translation into the EM spectrum, best.
Visible light spectrum shows the 'presence' of matter best.
Thus NASA's chioce of wavelengths for the LCROSS imaging.

The visible light spectrum and infrared are both EM, and not at all far apart in wavelength. Where the peak wavelength lies is determined by the temperature of the products of the collision, and can just as easily be in the visible wavelengths as the IR. In this case, the collisional energy is pretty low (less than 1e10 joules), so I expect the anticipated temperatures were low as well, hence the decision to include IR observations. IR was used for the Earth-based observations primarily because this is required by adaptive optics systems used to boost resolution.

Mid-infrared (3-8 µm) is equally sensitive to room temperature & to reflected sunlight
but it is particularly sensitive to thermal temperatures around 600º C
http://cimss.ssec.wisc.edu/goes/rt/view ... ct=gsc_b17

Mid-infrared is used for earth-based observations primarily to:
1) detect the thermal signature of fires
2) see best through water vapor & cirrus clouds and
3) distinguish white snow from white clouds.

The ends of the mid-infrared are particularly sensitive to
1) ice [3 µm] and 2) water vapor [5-8 µm]

kovil wrote: Personally, I expect a low water presence, which will be disappointing for habitation requirements. As comets are exactly the same composition as asteroids (comets are NOT dirty ice balls) they contribute no water to the Moon when they are accumulated by the Moon. Solar wind particulate is likely the culpret for the 'hydrogen presence' detected by previous satellite imagery, and is most likely an extremely thin and tenuous veil upon the lunar surface only.

ta152h0 wrote:He was asking his coworkers if the moon was going to be around after the impact.

Chris Peterson wrote:

kovil wrote:Remember, these images are in the infrared, which shows kinetic energy's translation into the EM spectrum, best.
Visible light spectrum shows the 'presence' of matter best.
Thus NASA's chioce of wavelengths for the LCROSS imaging.

The visible light spectrum and infrared are both EM, and not at all far apart in wavelength. Where the peak wavelength lies is determined by the temperature of the products of the collision, and can just as easily be in the visible wavelengths as the IR. In this case, the collisional energy is pretty low (less than 1e10 joules), so I expect the anticipated temperatures were low as well, hence the decision to include IR observations. IR was used for the Earth-based observations primarily because this is required by adaptive optics systems used to boost resolution.

jerbil wrote:It might be maintained that a meteorite is either rocky or iron-nickel, but surely our knowledge is based on that which arrives at the surface of the Earth, from which any volatiles may have disappeared. But what about Kuiper belt objects, or even objects in the Oort cloud?

kovil wrote:Remember, these images are in the infrared, which shows kinetic energy's translation into the EM spectrum, best.
Visible light spectrum shows the 'presence' of matter best.
Thus NASA's chioce of wavelengths for the LCROSS imaging.

As comets are exactly the same composition as asteroids (comets are NOT dirty ice balls) they contribute no water to the Moon when they are accumulated by the Moon.