The thread for space cadets!

[peter grimes]

Oooh!! Can we start talking about Astrophotography here?

I've barely started to dabble.

I'm lucky enough to have access to an 8" Meade Cassegrain-Schmidt, and I own a Nikon D3200. This summer I got the adaptors to make them "kithh", but I opted for the off-brand cheapos. Don't make the same mistake!! There's lash in the t-ring adaptor, and that's unacceptable for quality work.

There are some software packages available to assist in processing and frame-stacking, but I haven't yet used any of those. I'm on an iMac, and all the free stuff is Windows / Linux. I'm not sure if it's worth running a VirtualMachine for this sort of stuff, since it's very processor-intensive.

Just about everything I've been reading up on comes from reddit.com/r/astrophotography

 

[uppi]

Oooh!! Can we start talking about Astrophotography here?

Wait...there is more to astrophotography than sticking a camera to the end of a telescope?

I guess the problem is that consumer telescopes are built for the human eye, and it takes some optics to adjust that for a camera.

There are some software packages available to assist in processing and frame-stacking, but I haven't yet used any of those. I'm on an iMac, and all the free stuff is Windows / Linux. I'm not sure if it's worth running a VirtualMachine for this sort of stuff, since it's very processor-intensive.

For simple image processing tasks I would recommend ImageJ, which is free, quite powerful and should have a Mac version.

For more complex tasks, there is a point where you want an programming environment with libraries for image processing. MATLAB is quite good at that, but way too expensive for hobby projects.

 

[PlutonianEmpire]

Been meaning to post this all day, but IRL is a female dog, as always.

But this should be in a similar vein as astrophotography. I think....

http://www.nasa.gov/content/goddard...elps-amateur-astronomers-detect-alien-worlds/

NASA-funded Program Helps Amateur Astronomers Detect Alien Worlds

A new program will let amateur astronomers detect exoplanets – worlds outside our solar system – by observing nearby bright stars and recording faint dips in their brightness caused by transits from planets in orbit around them.

The program is called Open Source Differential Photometry Code for Amateur Astronomy Research (OSCAAR) and was developed in part with NASA funding. It is available for free online at:

http://oscaar.github.io/

"From NASA's Kepler mission, we know there are potentially thousands of exoplanets or more," said Brett Morris, a research associate at NASA's Goddard Space Flight Center in Greenbelt, Md., who is lead developer of the OSCAAR program. "These planet candidates were discovered by looking at the brightness of thousands of stars over time. A certain fraction of the planets orbiting those stars are aligned such that they transit the star -- that is, they pass in front of the star as seen from earth. The transit will block out just a small amount of that star's light when we view it from Earth. If we measure that star's brightness over time, it will change by up to two or three percent, which can be measured by the commercial-grade detectors that many amateur astronomers and small observatories at academic institutions already have."

 

[peter grimes]

OK, here's a neat visualization of the observational orbits of J002E3 - a near earth asteroid.

What I find very curious are the multiple intersections of different orbits that happen to coalesce on different points of the Moon's orbit. Perhaps this is only an artifact of the 2D rendering - or is this a natural phenomenon of most bodies that get involved with the Earth-Moon system before being ejected?

 

[hobbsyoyo]

My guess is the rendering is throwing things off but IDK.

By the way,
Orbital Sciences launched an Antares rocket with Cygnus cargo carrier to the station today. The launch went smoothly; interstingly: the Antares uses engines left over from the Soviet Moon Rocket, N1. I can write up a history of that project if anyone is interested.

 

[Crezth]

Orbital Sciences is a cool example of non-SpaceX private space working well. That was a neat launch.

 

[SouthernKing]

What I find very curious are the multiple intersections of different orbits that happen to coalesce on different points of the Moon's orbit. Perhaps this is only an artifact of the 2D rendering - or is this a natural phenomenon of most bodies that get involved with the Earth-Moon system before being ejected?

It's definitely the rendering.

 

[uppi]

I disagree, that is not the rendering, that is the effect of the moon you see there. When the asteroid enters its orbit around earth, it is very close to the moon. it seems that it gets dragged into that orbit by the moon, otherwise the orbit would look quite different. because of this, the parameters of the orbit are not that different than those of the moon's orbit, so it spends a lot of time in the vicinity of the moon orbit. If you look at the situation when the asteroid leaves the orbit, the moon is also very close to it, so I would say that it is the moon again which kicks the asteroid out.

This seems to be a particular feature of two heavy bodies and one very light body. Just the earth and the asteroid would not result in such an orbit.

 

[peter grimes]

Are we talking about the same phenomenon?

I was specifically interested in the 4 apparent intersections of the asteroid with the Moon's orbit, at roughly:
20 degrees,
160,
210,
340.

 

[uppi]

Are we talking about the same phenomenon?

I was specifically interested in the 4 apparent intersections of the asteroid with the Moon's orbit, at roughly:
20 degrees,
160,
210,
340.

Maybe not

I would still guess it is the effect of the moon. The points at 160 and 210 degrees are pints where the moon came quite close to the asteroid and those somehow define the point at 20 degrees. The one at 340 seems to be more of a coincidence, though. But thats all a bold guess, without a simulation, I wouldn't put much weight behind that statement.

The two orbits seem to be more or less in plane (another guess, though), so I would be hesitant to call it an effect of the projection into 2D.

 

[hobbsyoyo]

I disagree, that is not the rendering, that is the effect of the moon you see there. When the asteroid enters its orbit around earth, it is very close to the moon. it seems that it gets dragged into that orbit by the moon, otherwise the orbit would look quite different. because of this, the parameters of the orbit are not that different than those of the moon's orbit, so it spends a lot of time in the vicinity of the moon orbit. If you look at the situation when the asteroid leaves the orbit, the moon is also very close to it, so I would say that it is the moon again which kicks the asteroid out.

This seems to be a particular feature of two heavy bodies and one very light body. Just the earth and the asteroid would not result in such an orbit.

Maybe not

I would still guess it is the effect of the moon. The points at 160 and 210 degrees are pints where the moon came quite close to the asteroid and those somehow define the point at 20 degrees. The one at 340 seems to be more of a coincidence, though. But thats all a bold guess, without a simulation, I wouldn't put much weight behind that statement.

The two orbits seem to be more or less in plane (another guess, though), so I would be hesitant to call it an effect of the projection into 2D.

You can't really make these assumptions from a top-down 2d rendering. The astreroid could never even come close to the moon if it passes the moons orbit at a point hundreds of thousands or millions of kilometers above or below it.

It is also possible, even probable, that the asteroid crosses the moon's orbit as it does for reasons that have nothing to do with the moon. The Earth's gravity is so much stronger than the moon's that it alone could determine the major shape of the asteroids orbit with the moon having very little influence.

 

[Winner]

By the way,
Orbital Sciences launched an Antares rocket with Cygnus cargo carrier to the station today. The launch went smoothly; interstingly: the Antares uses engines left over from the Soviet Moon Rocket, N1. I can write up a history of that project if anyone is interested.

The engines are awesome; the one thing in which the Russians were (and still are) ahead of the West.

 

[hobbsyoyo]

The engines are awesome; the one thing in which the Russians were (and still are) ahead of the West.

Yup!

Although the Merlin 1D's have the highest thrust-to-weight ratio of any rocket, they're the exception to the rule of mediocrity.

 

[LamaGT]

Yup!

Although the Merlin 1D's have the highest thrust-to-weight ratio of any rocket, they're the exception to the rule of mediocrity.

Aren't the Merlins actually based on the N1 as well?

 

[hobbsyoyo]

No, they are a new, in-house SpaceX design with open-cycle combustion sequence. The N-1's NK-15/33's used a more efficient, closed-cycle combustion sequence.

 

[uppi]

You can't really make these assumptions from a top-down 2d rendering. The astreroid could never even come close to the moon if it passes the moons orbit at a point hundreds of thousands or millions of kilometers above or below it.

It is also possible, even probable, that the asteroid crosses the moon's orbit as it does for reasons that have nothing to do with the moon. The Earth's gravity is so much stronger than the moon's that it alone could determine the major shape of the asteroids orbit with the moon having very little influence.

I am not making the assumptions, I am seeing the influence of the moon. The path of the asteroid is certainly not two-body physics (i.e. Kepler's laws), so it has to be (at least) a three-body effect. I agree that the Earth alone could determine the shape of the asteroids orbit, but that would not result in such an orbit. If it was just the earth, the Earth would not capture the asteroid, but slingshot it back into space on the first pass. So you need a third body, and the most probable one is the moon. That is just basic momentum conservation. That the largest deviations from the orbit determined by Earth's gravity happen, when the moon is close by in the projection is further evidence that there is an influence of the moon. You might be able to argue that the sun is the third body, but I think that's unlikely.

If the asteroid is influenced by the moon at several points of its orbit around the earth, then it is also likely that their orbits are roughly in plane. Otherwise they would interact at one point, but be far away from each other at the other point.

 

[Crezth]

The engines are awesome; the one thing in which the Russians were (and still are) ahead of the West.

That's a bold claim. Why do you say this? Do you just mean rocket engines or...?

 

[hobbsyoyo]

I am not making the assumptions, I am seeing the influence of the moon. The path of the asteroid is certainly not two-body physics (i.e. Kepler's laws), so it has to be (at least) a three-body effect. I agree that the Earth alone could determine the shape of the asteroids orbit, but that would not result in such an orbit. If it was just the earth, the Earth would not capture the asteroid, but slingshot it back into space on the first pass. So you need a third body, and the most probable one is the moon. That is just basic momentum conservation. That the largest deviations from the orbit determined by Earth's gravity happen, when the moon is close by in the projection is further evidence that there is an influence of the moon. You might be able to argue that the sun is the third body, but I think that's unlikely.

If the asteroid is influenced by the moon at several points of its orbit around the earth, then it is also likely that their orbits are roughly in plane. Otherwise they would interact at one point, but be far away from each other at the other point.

You are making two assumptions:
1) That the asteroid is passing close to the moon
2) The orbital path we see is in large part due to the moon's influence.

I'm saying we can't say either are the case without a better perspective and actually doing the orbital equations. You can say two-body this, three body that, but it's an empty claim without actually doing the equations. The presented video misses the entire third dimension, which can royally screw with us and mislead what we think we see. You also earlier stated that the orbits look planar - which is another bad assumption. Not to beat up on you, but it's actually a terrible assumption because that asteroid can come in at angle to earth's orbital plane but from a 2-d perspective, it looks planar because in 2-d it is.

One other thing, even in a two body system, if you simplify the earth as a perfectly flat sphere, then you can draw some conclusions on how the asteroid would act. But that's another bad simplification as the lumpiness and squashed nature of the earth significantly effect orbital trajectories.

 

[peter grimes]

the lumpiness and squashed nature of the earth significantly effect orbital trajectories.

Seriously? I didn't think that graviational anomalies on the scale of Everest or the deep oceans could have enough of an effect on something like this. Satellites, maybe.. I mean, I don't know anything about this but it seems to me that since the Tibetan Plateau is a relatively tiny bump on the scale of the whole planet, the gravitational anomaly would be washed out by the rest of the mass around and behind it.

4500m is the average elevation, and the earth is 6 x 10^6 m - so we're talking .1% change in that one spot. It really has an effect?

 

[hobbsyoyo]

Nah you're right