Stargazing Event Horizon Telescope Results Released Yesterday (April 10, 2019)

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davenn

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An obvious way to get more baseline for VLBI is to go into outer space, but not many radio-astronomy satellites have been launched, satellites like HALCA and Spektr-R.

well there is a much easier way and it doesn't involve the massive cost of space based scopes and it also gives a massive VLBI
... namely observations 6 months apart on opposite sides of the Earth's orbit, an approx 300 million km baseline :smile:


D
 
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The observations have to be simultaneous for this to work.
 

PAllen

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The observations have to be simultaneous for this to work.
I assumed the smiley meant @davenn was well aware of this.
 

davenn

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The observations have to be simultaneous for this to work.
I assumed the smiley meant @davenn was well aware of this.

Actually, they don't, the data can be collected with good timing and then sync'ed once all data is collected
this is just the same for the Earth based radio telescopes that were involved in the M87 observations

NOT ALL of them could see M87 at the same time .... as we don't live on a flat earth, simultaneous obs's are impossible


Dave
 
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You cannot use that baseline for VLBI in the way the Event Horizon telescope did if you take the data 6 months apart. You need to record the same waveforms at multiple places to do interferometry.
NOT ALL of them could see M87 at the same time
But always more than one when they took data, otherwise recording data would have been pointless.

Independent of the physics: Think about it for a second. Would they have made an image with a <10,000 km baseline if there was a way to get a baseline 30,000 times longer with the same telescopes?
 

davenn

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You cannot use that baseline for VLBI in the way the Event Horizon telescope did if you take the data 6 months apart. You need to record the same waveforms at multiple places to do interferometry.
But always more than one when they took data, otherwise recording data would have been pointless.

and there you just contradicted yourself 😄 :wink:
6 hours or 6 months, don't make any difference and there would still be more than one observing at the 6 months apart


D
 
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and there you just contradicted yourself 😄 :wink:
No I didn't. Maybe you misread my post?
You need simultaneous observations. 6 hours time difference between telescopes would ruin it in the same way 6 months do. The Event Horizon Telescope only used data where at least two telescopes could observe at the same time - more are better.
 

Orodruin

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6 hours time difference between telescopes would ruin it in the same way 6 months do.
Depending on the distance between the telescopes ... 😉
The point is that you need to observe the same wave front. That is how you do interferometry.
 
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well there is a much easier way and it doesn't involve the massive cost of space based scopes and it also gives a massive VLBI
... namely observations 6 months apart on opposite sides of the Earth's orbit, an approx 300 million km baseline :smile:


D
If it was this easy, it could have been done in the '70s, maybe even the '60s
 

davenn

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If it was this easy, it could have been done in the '70s, maybe even the '60s
think about what you wrote
now think about the available technology at that time

so no, it couldn't have been done
 

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