Starship Asterisk*

Keyman wrote:

Further, just last year the 50-meter wide asteroid 2012 DA14 was discovered that will pass inside the orbit of Earth's geosynchronous satellites this coming Friday. A collision with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate. One likely result is a global extinction of many species of life, possibly dwarfing the ongoing extinction occurring now.

Really guys? A posting with the above exerpt, and we're discussing what filters were used for the picture??

What would Mariesa van Huyten say? :wink:

Further, just last year the 50-meter wide asteroid 2012 DA14 was discovered that will pass inside the orbit of Earth's geosynchronous satellites this coming Friday. A collision with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate. One likely result is a global extinction of many species of life, possibly dwarfing the ongoing extinction occurring now.

neufer wrote:

Chris Peterson wrote:
Of course, the path of the asteroid is curved, as well. It isn't visually apparent in such a narrow field (although it could probably be measured instrumentally), but the actual curve is a convolution of the fast orbital motion of the telescope and the slower orbital motion of the asteroid.

Convolution isn't quite the right word. Combination, conflation...

• v_a(t)= position vector of the asteroid
  
  v_e(t)= position vector of the Earth
  
  v_h(t)= position vector of Hubble [ = (v_h(t)-v_e(t)) + v_e(t) = (Hubble orbit) + Earth orbit ]
  
  v_ah(t)= [v_a(t)-v_h(t)] = relative position vector of asteroid vis-à-vis Hubble
  
  n= unit Hubble pointing vector (in celestial coordinates).
  
  P_n(t) = n x (n x v_ah(t))/(n ⋅ v_ah(t))
  where P_n(t)= path vector of the asteroid in the Hubble(/camera obscura) image plane.

gratefulguy wrote:With very limited knowledge of astronomy, I ask the group's indulgence in wondering if the other (shorter) blue lines indicate other asteroids and are the yellow lines just an artifact of the imaging process, or do they denote movement of some other type of object?
Thanks to all who bring this website to us.

Chris Peterson wrote:

Beyond wrote:Which is why i don't try to figure out and keep track of filters and wave lengths. It gives me a headache I'm just not photo-astrologically minded. I just look at the pretty pictures.

Well, in an image like this there's no need to know the specifics of the filters used, and little need to know the specifics of the color map used. But it is necessary to understand that this is a stack of two images, each mapped to a different color, or much of what we see becomes impossible to interpret.

neufer wrote:Correction: Think of the apparent motion of Ents in front of a fixed full moon as observed from a moving car or train.

neufer wrote:Convolution generally implies some sort of universal smearing out such as an exact global cluster image as convolved (i.e., smeared out) with the tiny Airy disk (+ diffraction spikes) of the Hubble (or, unfortunately, the ugly Response Function of the original miss-focused Hubble).

Chris Peterson wrote:

neufer wrote:Convolution isn't quite the right word. Combination, conflation...

Actually, I think its the most technically accurate word, since we are looking at a curve described by a new function created by the mathematical convolution of two other functions (one describing the motion of the HST, and one by the motion of the asteroid). However, the other words you suggest are also descriptive of what's going on, in a less mathematical sense.

neufer wrote:Convolution isn't quite the right word. Combination, conflation... :?:

Correction: Think of the apparent motion of Ents in front of a fixed full moon as observed from a moving car or train.

Chris Peterson wrote:

neufer wrote:

stephen63 wrote:
What does it indicate when the asteroid has such a curved path?

You are observing the curved path of the Hubble, itself, in its orbit.

(Think of the apparent motion of trees in front of a fixed full moon as observed from a car or train.)

Of course, the path of the asteroid is curved, as well. It isn't visually apparent in such a narrow field (although it could probably be measured instrumentally), but the actual curve is a convolution of the fast orbital motion of the telescope and the slower orbital motion of the asteroid.

Chris Peterson wrote:Where did you find information on the filters used for the two exposures?

Beyond wrote:Which is why i don't try to figure out and keep track of filters and wave lengths. It gives me a headache :!: I'm just not photo-astrologically minded. I just look at the pretty pictures. :lol2:

Chris Peterson wrote:

geckzilla wrote:It ends up looking cyan and yellow because both filters used are combined 50/50 to produce the green channel.

Right, which is just the mechanism used to map the two images to cyan and yellow. That's why we see no red, no blue, and no green in the image.

geckzilla wrote:It ends up looking cyan and yellow because both filters used are combined 50/50 to produce the green channel.

Chris Peterson wrote:(I don't think that the mapping used here was blue and red, but rather cyan and yellow. It is the white objects that were detected by both filters. Where did you find information on the filters used for the two exposures?)

Ann wrote:By the way, why are most of the streaks so blue? Well, it's because this picture was made using only two filters, 606 nm and invisible infrared at 814 nm. (I believe that the orange filter can also be described as "clear", meaning that it detects all visible light.) The objects detected by the orange or visible filter are shown as blue, and the objects detected by the infrared filter as red. Yellow objects are detected by both the infrared and the orange filter.

neufer wrote:

stephen63 wrote:What does it indicate when the asteroid has such a curved path?

You are observing the curved path of the Hubble, itself, in its orbit.

(Think of the apparent motion of trees in front of a fixed full moon as observed from a car or train.)

Messican wrote:
Tomorrow's picture; What's a scupture?

• It's a scup sculpture.

http://en.wikipedia.org/wiki/Scup wrote:

<<"Scup" is a shortened form of a Narragansett word like mishcùppaûog. The scup, Stenotomus chrysops, is a fish which occurs primarily in the Atlantic from Massachusetts to South Carolina. Another English name for the fish, paugie, is a shortening of the same word which simply removes the other side of it. Along with many other fish of the family Sparidae, it is also commonly known as porgy. Scup grow as large as 18 in and weigh 3 to 4 lb, but they average ½–1 lb. In the Middle Atlantic Bight, scup spawn along the inner continental shelf. Their larvae end up in inshore waters, along the coast and in estuarine areas. At two to three years of age, they mature. Scup winter along the mid and outer continental shelf. When the temperature warms in the spring they migrate inshore. They are fished for by commercial and recreational fishermen. They are a fine fish to eat because of their light flavor and are sometimes called panfish. Popular methods of cooking include but are not limited to frying, broiling and baking.>>

stephen63 wrote:
What does it indicate when the asteroid has such a curved path?

http://hubblesite.org/newscenter/archive/releases/1998/10/text/ wrote:
<<The Hubble images capture an asteroid as a long trail produced by its motion across the camera's field of view. The trails appear like the streaks of light found on photos taken at night of speeding cars with their headlights on. In Hubble's case, asteroid trails show a unique curvature due to the continuously shifting position of the telescope as it orbits the Earth. This effect, known as parallax, allowed Evans and Stapelfeldt to determine distances and sizes for the asteroids spied by Hubble. A similar parallax effect is the key to depth perception in human vision: our eyes are set apart so that we can see three dimensionally.

"Asteroid trails observed by the Hubble telescope are usually curved because the telescope travels in a curved low- Earth orbit," Stapelfeldt says. "By precisely measuring the shape of the trails, we can solve for the distance to each asteroid at the time it was observed. It isn't possible to do this using a stationary telescope on the ground.">>