There's a fantastic BBC Horizon documentary called, "Seeing Stars" which includes, among other things, a SOFIA mission: http://www.dailymotion.com/video/x1kacli_bbc-horizon-2011-se...
The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
31–40 of 47 posts
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#32Earlier quoted context omitted.
It's normal to take many short exposures and stack them up to get a long one. The length is dictated by the amount of noise in your detector. From a look at the Wikipedia article, it looks like they need a lot more than just short exposures on Sofia.
Yes, you can stack short exposures, but long exposures are better in astrophotography (as a single 10 second exposure has a higher signal-to-noise ratio than 10x 1s exposures). If you take it to the extreme, it's very difficult to differentiate between the signal and the noise if your exposures are really short, which makes astrophotography in cities without a tracking quite mount difficult.
Can you explain the cause of the difference between one long exposure and stacking short exposures? I'd naively expect one 10s exposure to produce equivalent data to 10x1s exposures.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#33Earlier quoted context omitted.
Agreed, unfortunately meaningful projects such as this are not a high priority for the US electorate (and thus the US Congress) [1]. My hope is that growing interest by college students in STEM subjects [2] will ultimately lead to an increased understanding of the importance of these projects in the long term. [1] http://en.wikipedia.org/wiki/Budget_of_NASA [2] https://www.stemconnector.org/sites/default/files/store/…
One could always ask for support saying a given experiment could prove the, say, biblical flood or somethimg equally silly. If someone believes that all animals on Earth descend from the living cargo of a wooden ship, it should be possible to convince them of anything . Hacking a right-wing nutty congresscritter is an intriguing concept.
And, I guess, Bill Maher is a right-wing nutty? He believes Mars and Moon missions would be a great waste of money.
The Bible isn't holding us back....it's our lack of imagination and lazy jokes and the conflation of capital and fiat currency.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#34Earlier quoted context omitted.
Yes, you can stack short exposures, but long exposures are better in astrophotography (as a single 10 second exposure has a higher signal-to-noise ratio than 10x 1s exposures). If you take it to the extreme, it's very difficult to differentiate between the signal and the noise if your exposures are really short, which makes astrophotography in cities without a tracking quite mount difficult.
Can you explain the cause of the difference between one long exposure and stacking short exposures? I'd naively expect one 10s exposure to produce equivalent data to 10x1s exposures.
What I suspect nawitus is referring to involves the read noise of a CCD. There is always some low level noise involved in reading out a CCD. If this noise dominates, which may be the case for amateur astrophotography, it can explain the noise difference between a single exposure and stacking an equivalent number of shorter exposures.
If for the sake of illustration, the read noise is 10 counts and the signal for a 1 second observation is 10 counts, you will have a signal to noise of 1. Stacking 10 of these will give you a signal to noise of ~3 (square root of 10). Conversely, for the 10 second observation, you will have 100 counts for a signal to noise of 10.
However, there are other sources of noise, and instruments at major observatories are generally designed such that the read noise is not the dominant source of error either through more sensitive detectors or gathering more light (a bigger telescope or larger pixels) or some other means. If even a short exposure constitutes 1000000 counts, the difference between one 10s exposure and ten 1s exposures will be negligible.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#35Earlier quoted context omitted.
Can you explain the cause of the difference between one long exposure and stacking short exposures? I'd naively expect one 10s exposure to produce equivalent data to 10x1s exposures.
What I suspect nawitus is referring to involves the read noise of a CCD. There is always some low level noise involved in reading out a CCD. If this noise dominates, which may be the case for amateur astrophotography, it can explain the noise difference between a single exposure and stacking an equivalent number of shorter exposures. If for the sake of illustration, the read noise is 10 counts and the signal for a 1…
Exactly the sort of thing I was looking for. Thanks for the explanation, it makes perfect sense. I hadn't realized that there would be sources of noise that hit you for each read.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#36Here is one of the runs they did last year:
http://flightaware.com/live/flight/NASA747/history/20130717/...
The arches are when they are doing their observations.
Edit: For some reason the map is centering over the Atlantic when I open the link, the flight path is actually from New Zealand if you can't see it to start with.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#37During one of my many Lyft rides I learned the driver was also one of several managers on this project. We had an interesting chat about it, and it left me wishing that the people involved in this sort of work were paid substantially more.
oh interesting. I'm also a lyft driver/scientist. I'm doing a series of in-car interviews of scientists, I'd love to try to talk to him, would you be able to contact me (details in profile)?
Scientists in Sedans getting Sauced?
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#38I wonder if the plane flies during the day or night? I would assume that for a given mission its one or the other, which makes me also wonder how fast or slow it flies. Even though it is looking in the infrared - wouldn't the daylight still affect it?
We only fly at night. Well, technically speaking, we can observe with the sun up, but the guider cameras are optical which makes it nearly impossible to track any targets when the sky is bright. Moreover, we have to stay well away from the sun as the telescope would focus the sunlight with enough intensity to destroy itself. So, yeah, we only fly at night. Airspeed is roughly mach 0.85.
Do you have more info about the airplane performance? I'm working on a flight simulator and this plane is one of the 747's we're going to add.
I'd love to get more details about the differences compared to a regular 747SP.
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#39Earlier quoted context omitted.
One could always ask for support saying a given experiment could prove the, say, biblical flood or somethimg equally silly. If someone believes that all animals on Earth descend from the living cargo of a wooden ship, it should be possible to convince them of anything . Hacking a right-wing nutty congresscritter is an intriguing concept.
And, I guess, Bill Maher is a right-wing nutty? He believes Mars and Moon missions would be a great waste of money. The Bible isn't holding us back....it's our lack of imagination and lazy jokes and the conflation of capital and fiat currency.
... or both you and the GP are partially right and _both_ are holding us back. :/
Re: The Jet With a 17-Ton Telescope That NASA Uses as a Flying Observatory
#40During one of my many Lyft rides I learned the driver was also one of several managers on this project. We had an interesting chat about it, and it left me wishing that the people involved in this sort of work were paid substantially more.
Agreed, unfortunately meaningful projects such as this are not a high priority for the US electorate (and thus the US Congress) [1]. My hope is that growing interest by college students in STEM subjects [2] will ultimately lead to an increased understanding of the importance of these projects in the long term. [1] http://en.wikipedia.org/wiki/Budget_of_NASA [2] https://www.stemconnector.org/sites/default/files/store/…
NASA is so prestigious that they basically can get away with paying everyone very little. They aren't stuck with bottom of the barrel people even though they pay them bottom of the barrel wages.
I'm not saying it's right or wrong, but I don't think more funding would really change much (other than allow them to fund more projects, but I'd argue that there are some serious diminishing returns at this point)