Apollo 16 Flag is Still Casting Shadows

Phage
reply to post by cestrup

 

More evidence the journalist made stuff up (or, at best, did not understand what he was being told).

The first attempt to spot the spacecraft will be made using only one of the VLT's four telescope mirrors, which are fitted with special "adaptive optics" to cancel the distorting effect of the Earth's atmosphere.

This makes no sense, there is no possibility whatsoever that an 8.2 meter telescope could image Apollo landers. It would require a telescope with a 100 meter mirror. blogs.discovermagazine.com...

BTW, here is an infrared image of the Moon from the VLT. Taken in April of 2002, before the article was published, it has a resolution of 130 meters.
www.eso.org...

edit on 4/15/2014 by Phage because: (no reason given)

with all due respect, I think we're discussing different things. I'm merely going by the quotes in the article. What the journalist writes in between are neither here nor there. Both men seemed to think they could gather images by what they were quoted saying. So do you have anything of these men refuting what they said in this article? You'd think if the journalist was twisting their quotes there'd be some mention of it somewhere. I know many scientists would want the air to be cleared if someone journalist were quoting them as being intellectually dishonest.

So, do you think these two scientists were being misquoted? Or were they just wrong?

onebigmonkey

cestrup
reply to post by Rob48

 

No, JW got that from the horse's mouth. This is from a press release:

"the astronomers were able to see details on the scale of one milli-arcsecond, corresponding to being able to distinguish, from the Earth, the headlights of a car on the Moon."

amber.obs.ujf-grenoble.fr...

edit on 15-4-2014 by cestrup because: (no reason given)

And as pointed out this is not an optical telescope that they are talking about, and that result is not talking about actually seeing something on the moon, it is discussing something 300 light years away and using a simple analogy.

So, why would they measure resolution in arc-seconds?

edit to add: isn't it considered an optical/near infrared telescope?

Also, as Phage illustrated -- It seems the VLT can produce some nice images of the moon. Maybe the scientists believed they could harness more of its power and resolve some cool images of the Apollo landings.

cestrup

So, do you think these two scientists were being misquoted? Or were they just wrong?

Based on my experience as a subeditor trying to un-mangle journalists' versions of science, I'd go with misquoted.

If you look at the actual story, which is here: www.telegraph.co.uk...

you can see that the only directly relevbant quote from West is "They would most probably be sufficiently sharp to show something at the sites". "Something", not the landers themselves. Perhaps he was thinking of possibly using the interferometer to look for a long shadow at a low sun angle. That possibility is mentioned in the email linked by Phage, which I have no reason to disbelieve is genuine: the names and facts check out.

So, why would they measure resolution in arc-seconds?

edit to add: isn't it considered an optical/near infrared telescope?

Arcseconds is just a measure of angular size: the apparent size of an object in the field of view.

I think you are getting confused between the two instruments. The VLT is indeed a visible/near-IR telescope. But the VLTI, which is what has the 2 milliarcsec resolution, is an interferometer. Basically it takes images from four separate telescopes and combines the light, and gains information from the patterns of interference fringes that result. It's not taking an image that you or I would interpret as a photograph, although they can be combined to produce nice images. All this only works for small point sources of light though.

reply to post by Rob48


Dr Richard West, an astronomer at the VLT, confirmed that his team was aiming to achieve "a high-resolution image of one of the Apollo landing sites".

There's this one too.

cestrup
reply to post by Arbitrageur

 

@ Rob - the picture you posted of a city scape looks much more resolute to me than the LRO photos.

Without an atmosphere to soften the shadows like on Earth, the Moon images have harsh contrast. LRO images we've seen are also in B&W.

Let's adjust that city image to simulate it being taken in vacuum and in B&W:


Not so lovely and detailed now, is it?

wildespace

cestrup
reply to post by Arbitrageur

 

@ Rob - the picture you posted of a city scape looks much more resolute to me than the LRO photos.

Without an atmosphere to soften the shadows like on Earth, the Moon images have harsh contrast. LRO images we've seen are also in B&W.

Let's adjust that city image to simulate it being taken in vacuum and in B&W:

Not so lovely and detailed now, is it?

No offense, my man but that looks far less pixelated than the LRO photos.

reply to post by cestrup


Again, it is because your mind is able to fill in details because you can identify the various sorts of objects. The lunar surface looks like a jumble at every scale.

Rob48

cestrup

So, do you think these two scientists were being misquoted? Or were they just wrong?

Based on my experience as a subeditor trying to un-mangle journalists' versions of science, I'd go with misquoted.

If you look at the actual story, which is here: www.telegraph.co.uk...

you can see that the only directly relevbant quote from West is "They would most probably be sufficiently sharp to show something at the sites". "Something", not the landers themselves. Perhaps he was thinking of possibly using the interferometer to look for a long shadow at a low sun angle. That possibility is mentioned in the email linked by Phage, which I have no reason to disbelieve is genuine: the names and facts check out.

So, why would they measure resolution in arc-seconds?

edit to add: isn't it considered an optical/near infrared telescope?

Arcseconds is just a measure of angular size: the apparent size of an object in the field of view.

I think you are getting confused between the two instruments. The VLT is indeed a visible/near-IR telescope. But the VLTI, which is what has the 2 milliarcsec resolution, is an interferometer. Basically it takes images from four separate telescopes and combines the light, and gains information from the patterns of interference fringes that result. It's not taking an image that you or I would interpret as a photograph.

edit on 15-4-2014 by Rob48 because: (no reason given)

You're right, I did get the two confused. Now wasn't the image Phage posted from the VLTI? JW called it the "VLT Array" so I suppose he could have meant all four. And didn't the artcle from ESO suggest a resolution of 1 miiliarcsec for the VLTI?

Damn, this gets down right confusing? lol

cestrup

No offense, my man but that looks far less pixelated than the LRO photos.

"Looks". Looks can be deceptive. Shall we test that?

To avoid cries of foul I will go back to the original image at this page:

Zooming in in Photoshop until the individual pixels are visible. No resampling done: these are the original pixels.



A car appears to be about 12 pixels long. 12 x 30cm = 3.6 metres. That seems a little short even for a hatchback (a Ford Fiesta is 406cm long) but it's pretty close to the claimed resolution. If anything the resolution appears to be slightly worse than the claimed 30cm per pixel, unless those are very small cars!

Now the original-size LRO image from here:



I make the diameter of the main LM body (excluding legs) to be 16 pixels. 16 x 25cm = 4.0 metres. It's hard to be exact because the bright reflection is overwhelming the sensor.

Let's check that against the actual LM drawings:



Depending on precisely which measurement you take, the diameter is just over or just under 14ft. That is about 4.2 - 4.3 metres.

I'd say that compares pretty favourably, wouldn't you?

(excuse the fact that the pixels appear larger in the first image - I made them the same apparent size on my screen but ATS seems to resize images...)

cestrup
No offense, my man but that looks far less pixelated than the LRO photos.

I agree with you on that LRO images seems to be more pixelated than regular images taken on Earth. I don't know the reason for this, might have something to do with data compression as it gets sent to Earth. But even with this pixelation, there's still obviously something more going on in those images than just rocks and craters.

If you look at a whole LRO image strip that contains an Apollo site, scroll around to look at the ordinary lunar landscape, and then randomly come across what is alleged as an Apollo site, you will instantly know you're looking at something special. Have a go yourself: wms.lroc.asu.edu... (the Apollo site is slightly above the middle, and by the right edge)
Here's another strip with the same Apollo site: wms.lroc.asu.edu...

Find me a lunar rock that has a flat reflective top like the Descent Stage has, and casts the same kind of near-vertical shadow, and find me the tracks that look like astronauts' foot tracks, and I'll consider the claim that we're looking at nothing but the natural lunar terrain.

cestrup

You're right, I did get the two confused. Now wasn't the image Phage posted from the VLTI? JW called it the "VLT Array" so I suppose he could have meant all four. And didn't the artcle from ESO suggest a resolution of 1 miiliarcsec for the VLTI?

Damn, this gets down right confusing? lol

You mean this image? www.eso.org...

That is from a single 8.2 metre telescope, not from the interferometer.

The ESO press release did say "on the scale of one milli-arcsecond" for the VLTI, yes. Scientists like to talk in terms of orders of magnitude, so the difference between 1marcsec and 2marcsec is not too significant, really. It's of that order.

interesting video about light and shadows

Rob48

cestrup

You're right, I did get the two confused. Now wasn't the image Phage posted from the VLTI? JW called it the "VLT Array" so I suppose he could have meant all four. And didn't the artcle from ESO suggest a resolution of 1 miiliarcsec for the VLTI?

Damn, this gets down right confusing? lol

You mean this image? www.eso.org...

That is from a single 8.2 metre telescope, not from the interferometer.

The ESO press release did say "on the scale of one milli-arcsecond" for the VLTI, yes. Scientists like to talk in terms of orders of magnitude, so the difference between 1marcsec and 2marcsec is not too significant, really. It's of that order.

Yeah, I meant that image. Thanks for clearing that up! What would an image of the lunar landscape look like from the VLTI?

999zxcv

interesting video about light and shadows

Please describe the contents of the video, in compliance with Terms & Conditions. Pretty sure we have seen this content before, so don't waste everyone's time.

reply to post by cestrup

As far as I know (and this REALLY isn't my field of expertise!) you wouldn't be able to get a usable image of the lunar surface using the VLTI. Interferometry is designed for resolving very small sources of light against a dark background. The moon is much too big and bright for the technique to work (again, this is based on what I have read rather than any personal knowledge).

To quote from Olivier Hainaut at ESO (in the other thread Phage linked to)...

In any case, I am really sorry, but the observations would not work, if they were ever attempted. It is one of the most frustrating issue with interferometry: it works well only for small things on a dark background. Anything extended adds noise, but no details can be seen on it.

Another relevant quote from his email to explain a bit better what was meant:

The original claim was that with the VLTI (see below), we would be able to resolve details as small as the size of an astronaut on the Moon.

VLTI is the interferometer combining several telescopes of the VLT, which gives a resolution similar to that of a telescope whose diameter would be equal to the distance between the actual telescopes involved with the interferometer.

That claim is true, and VLTI routinely resolve details as small as that. See, for instance these results showing details on the surface of a star: [EDIT: original link is broken but this is the sort of image he was referring to: amber.obs.ujf-grenoble.fr... ]

The problem is that VLTI works only with "coherent sources" - in short, the light must come from very sharp objects (like a very distant star), and does not work with extended sources (like a patch of lunar soil). So, when we now refer to the Moon as an example for VLTI, we say "we would be able to distinguish the 2 headlights on a lunar rover" (as these are 2 sharp sources).

DJW001

999zxcv

interesting video about light and shadows

Please describe the contents of the video, in compliance with Terms & Conditions. Pretty sure we have seen this content before, so don't waste everyone's time.

Time is a thing god made plenty off to waste as we see fit and i did describe what was in the video it was about light and shadows


here is another interesting video for you to lol at

reply to post by Rob48


Well, bear with me here, Rob -- if West were speculating about seeing Apollo sites with the VLT/VLTI; which one would he be referring to? I'm assuming the latter

reply to post by cestrup


The quote mystifies me, I must admit. There is no way you could image Apollo hardware with the single VLT telescope. As shown the best image from that had a resolution of around 70 milliarcseconds (the VLT FAQ page gives a maximum possible resolution of about 50 milliarcsec which is still nowhere enough).

But I don't know why any expert would be suggesting using the VLTI to image the moon. It doesn't make sense.

My best guess at what happened is that the Telegraph journalist got confused and mixed up Dr West talking about the VLTI resolution and that somehow influenced him to "massage" the quotes to fit the story. It shouldn't happen (and the Telegraph is considered to be a fairly reputable paper) but, having working in the newspaper industry myself, I know that journalists are often pretty sloppy when it comes to quotes. They sometimes tend to have an idea in their head about what story they want to write, and then shoehorn in any available quotes, taken out of context, to fit with that. Again, it shouldn't happen (and in my capacity as a subeditor/fact-checker it's my job to weed out that sort of thing), but sadly it does.

Unfortunately Dr West has retired from ESO now (he is in his seventies) so it is unlikely anyone could easily reach him for clarification. After all that article was written more than 11 years ago.


*Edit quick explanation of what those resolutions mean... the moon has an apparent diameter of about 1865 arcseconds. Its diameter is about 3480km, so at the distance of the moon, 1 arcsec represents about 3480/1865 = 1.9km. So 1 milliarcsec represents a little under 2 metres at the distance of the moon. Based on that calculation, I'd say that even with the VLTI, the claim of "resolving the lunar rover headlights on the moon" is a little exaggerated! Resolving an object the size of an astronaut... maybe just about. But only with the VLTI, which is no good for taking pics of the moon!

reply to post by Rob48


I was under the assumption that this story happened because ESO wanted to get "high resolution pics" of the apollo sites. West and Messey seemed to think they were unless, of course, they were misquoted (throwing out all of the jibberish from the writer of that piece)