06 Sep 11
1 edit
Originally posted by PsychoPawnOut of the mouth of babes🙂 How bout this one:
I think you got your urls a little mixed up.
http://www.physorg.com/news/2011-09-lroc-images-sharper-views-apollo.html
The two URL's somehow got concacted together. I just look at the end of the URL to see if it matches and it did but the beginning was a bit off.
07 Sep 11
1 edit
this is old stuff and the hoax believers have already debunked it. i can't remember where, you'll have to scan the sites. the argument has to do with the fact that there is a better quality image of this exact site without visible tracks, while this out of focus image has visible tracks which suggests a nasa edit job.
--edit--if i remember correctly, it was on the open minds forum/john lear subforum. that's still a lot to look through, maybe you can ask around there.
07 Sep 11
1 edit
Originally posted by VoidSpiritThese are new photos, the lunar probe has been running for only a couple of years and they just altered the orbit so it came down to about 20 Km from the surface. If you look at the photo's you can see the tracks they left when they walked around very clearly, much better resolution then the ones that went before.
this is old stuff and the hoax believers have already debunked it. i can't remember where, you'll have to scan the sites. the argument has to do with the fact that there is a better quality image of this exact site without visible tracks, while this out of focus image has visible tracks which suggests a nasa edit job.
--edit--if i remember correctly, ...[text shortened]... orum/john lear subforum. that's still a lot to look through, maybe you can ask around there.
You have a link to what the hoaxers call refutations? I don't see how they can debunk these new photos.
08 Sep 11
1 edit
Originally posted by sonhouseperhaps that other argument was about alleged footprints at another alleged apollo landing site. i think the same argument would apply. we have a low quality/resolution image where craters are barely visible as fuzzy circles offset by clear as day- footprints.
These are new photos, the lunar probe has been running for only a couple of years and they just altered the orbit so it came down to about 20 Km from the surface. If you look at the photo's you can see the tracks they left when they walked around very clearly, much better resolution then the ones that went before.
You have a link to what the hoaxers call refutations? I don't see how they can debunk these new photos.
it was obvious they edited the previous image because we had a better quality image without visible footprints to counterbalance it. i'm calling edit on this one too. with today's technology, there is no excuse for fuzzy images. it's like they had better cameras in the 60's.
08 Sep 11
3 edits
Originally posted by VoidSpiritResolution is a matter of the size of the optics Vs the distance to the object in question.
perhaps that other argument was about alleged footprints at another alleged apollo landing site. i think the same argument would apply. we have a low quality/resolution image where craters are barely visible as fuzzy circles offset by clear as day- footprints.
it was obvious they edited the previous image because we had a better quality image without v nology, there is no excuse for fuzzy images. it's like they had better cameras in the 60's.
The Hubble has a 2 meter mirror, roughly, and can parse a 360 degree circle into about 25 million slices. You can work that out for yourself, the res of Hubble in terms of arc seconds is about 0.05 arc seconds.
If that scope was circling the moon at say 100 Km, 100,000 meters, That represents a circle of about 600,000 meters, way rounded of course. So that kind of scope would be able to get something like 25 mm of resolution on the surface of the moon if it were 100 km from the surface.
The Hubble is about 360,000 km from the moon, a circumference of about 2.1 million Km or 2.1 billion meters. Divide by 25 million and you come out with about 90 or so meters of resolution of surface detail on the moon.
Clearly not even close to see actual hardware on the moon much less footprints.
If I knew the resolution of the photo's newly released I could calculate the size of the mirror used but my guess is to get lunar probes to the moon would limit the mirror size to more like 1/10th of a meter, 100 mm, maybe even 200 mm size.
Say the mirror was 200 mm, then it would at best represent 1/10th the res of Hubble, or able to parse a circle into just 2.5 million parts. So lets run the numbers on that:
We already know the Hubble 100 km up from the moon would give something like 25 mm, about 1 inch of res. so that would make the res of 200 mm 10 inches at that distance. But it was more like 20 km up, so the res would be 5 times better or so, then 2 inches of res for that mirror.
2 inches may be enough to visualize an actual footprint but there may be artifacts introduced by the camera movement, it would be sweeping by at a high rate of speed and some smearing would be inevitable so the res may be just what we see, it looks to me like a couple of feet or so, 1/12th of the res of a fixed camera. So that is about the best we can expect till someone walks around with a camera on the sites up close and personal. I assume that will be done maybe in the next century.
09 Sep 11
Originally posted by sonhousei don't doubt it would be next century at least. we don't have the technology today to send humans safely to the moon and back. which makes me wonder if we had it 50 years ago.
So that is about the best we can expect till someone walks around with a camera on the sites up close and personal. I assume that will be done maybe in the next century.[/b]
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09 Sep 11
Originally posted by VoidSpiritNot consistently, we didn't. Apollo 13 proved that. But it was the height (depth?) of the Cold War. Safety and consistency were not nearly as important as a good agitprop stunt, and mere astronauts were expendable.
i don't doubt it would be next century at least. we don't have the technology today to send humans safely to the moon and back. which makes me wonder if we had it 50 years ago.
Richard
09 Sep 11
Originally posted by sonhouseActually its more complicated than that.
Resolution is a matter of the size of the optics Vs the distance to the object in question.
What also matters is the focus of the telescope and also the sensitivity and resolution of the sensor. The angle of sky a telescope covers depends on its curvature not on how big it is. How much light it can gather (and thus the required length of exposure) is determined by the size of the mirror. How many dots per picture, is determined by the sensor.
11 Sep 11
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Originally posted by twhiteheadYes but the fundamental limits will always be the size of the mirror or objective lens V the distance. There is a point at which you get diminishing returns from ever more sensitive detectors and well as the resolution from the sensors. Not sure how much improvement capability is there for detectors now, that has been an ongoing research focus for decades.
Actually its more complicated than that.
What also matters is the focus of the telescope and also the sensitivity and resolution of the sensor. The angle of sky a telescope covers depends on its curvature not on how big it is. How much light it can gather (and thus the required length of exposure) is determined by the size of the mirror. How many dots per picture, is determined by the sensor.
I Don't imagine there is going to be any kind of breakthrough at this point in time, more like small incremental improvements that would mostly be useful for astronomy or medical research.
12 Sep 11
Originally posted by sonhouseI disagree. For a fast moving camera, the critical formula includes light gathering capacity (mirror size), exposure time (must be faster if the camera is moving), and sensitivity and resolution of sensor.
Yes but the fundamental limits will always be the size of the mirror or objective lens V the distance. There is a point at which you get diminishing returns from ever more sensitive detectors and well as the resolution from the sensors.
All are fairly fixed parameters and cannot be adjusted in a spacecraft that cannot be serviced.
For Hubble however, there is the advantage that most of what it looks at is not moving, so it can have extremely long exposures:
http://en.wikipedia.org/wiki/Hubble_Deep_Field
Between December 18 and December 28, 1995—during which time Hubble orbited the Earth about 150 times—342 images of the target area in the chosen filters were taken. The total exposure times at each wavelength were 42.7 hours (300 nm), 33.5 hours (450 nm), 30.3 hours (606 nm) and 34.3 hours (814 nm), divided into 342 individual exposures to prevent significant damage to individual images by cosmic rays, which cause bright streaks to appear when they strike CCD detectors. A further 10 Hubble orbits were used to make short exposures of flanking fields to aid follow-up observations by other instruments.[4]
13 Sep 11
Originally posted by twhiteheadThat is all well and good to have Hubble pointed at stuff for days and such but that does not increase the resolution, only the sensitivity to weaker light sources. The moon is not a weak light source and of course you need fast reacting sensors and there are tricks you can play with moving cameras like making 3D images by taking successive frames in different locations, something spacecraft are good at, but you can't make a silk purse out of a sows ear. If you have a 25 mm scope you cannot get better than its limit of resolution no matter what you do.
I disagree. For a fast moving camera, the critical formula includes light gathering capacity (mirror size), exposure time (must be faster if the camera is moving), and sensitivity and resolution of sensor.
All are fairly fixed parameters and cannot be adjusted in a spacecraft that cannot be serviced.
For Hubble however, there is the advantage that mo ...[text shortened]... hort exposures of flanking fields to aid follow-up observations by other instruments.[4][/quote]
A 2 meter scope like Hubble has a res of about 0.05 arc seconds, pretty darn good.
A 200 mm scope is going to have about 0.5 arc second res at best.
A 20 mm scope does about 5 arc seconds. There is nothing you can do about that.
All the fast and ultra pixel cameras is not going to change that.
If you want 10 mm minimum feature size in your image and you are 100 Km away, you need X size mirror no matter what the camera does. That would be roughly 1/3 the res of the Hubble, about 0.15 arc second res and you would need about a 700 mm scope. If you had a 70 mm scope you would have 100 mm res at best.
That's why I thought the min. scope size was probably about 200 mm for the probe in orbit around the moon where they were about 20 odd Km above the surface.
They might get a bit better res if they could repeatedly image the same spot and do a bit of digital image trickery to increase the res a bit better than the pixel count but I don't think they are doing that yet anyway. That would all be post production stuff on Earth, wouldn't need to change anything on the probe.
It's too bad they don't have a 1 meter mirror on the moon probe that would have been awesome, 0.1 arc sec. res to start with....
13 Sep 11
Originally posted by sonhouseI am afraid I do not follow your logic at all. With a standard handheld digital camera, the formula for resolution includes lens size, zoom, sensitivity, exposure etc. I do not believe that resolution is ever limited by lens size. A cell phone camera with a 1mm can potentially take as good a picture as a camera with a 20mm lens if the zoom and sensitivity are sufficient.
If you have a 25 mm scope you cannot get better than its limit of resolution no matter what you do.
My understanding of a space telescope is that the zoom is determined by the curvature of the dish, not the size of the dish.