Urantia Book Forum

Urantia Book Discussion Board : Study Group
It is currently Fri Apr 03, 2020 11:00 pm +0000

All times are UTC - 7 hours




Post new topic Reply to topic  [ 32 posts ]  Go to page Previous  1, 2, 3
Author Message
PostPosted:  
Offline

Joined: Tue Apr 05, 2011 11:52 am +0000
Posts: 92
ubreader76 wrote:
(Curtis also believes that NASA has pictures of this architectural sphere -"Mother Ship" taken by the Casini-Saturn probe - See: http://www.helloearth.info and click on the NASA Connection - I verified this picture was pulled directly from NASA website in 2007).

The comments on the page http://helloearth.info/nasaconnection/n ... ction.html are not very informed. Contrast these two comments: The stars are the same stars in all 3 images and NASA/JPL directs Cassini to switch to a TELEPHOTO lens.... The basics of photography says that if you switch to a telephoto lens, the field of view will change, and thus you will not be able to see the same stars any more. After all, the telephoto lens would not be much of use if it did not change the field, would it?

The next thing being that there is no telephoto lens on the Cassini probe but it does have both a narrow field and a wide field camera, which does produce a similar effect. See http://saturn.jpl.nasa.gov/spacecraft/c ... ssdetails/ for details. The wide field camera has a field of view of 60microradians x 1024 pixels = 61.4 milliradians in total. That equals 3.5 degrees. The narrow field camera is one tenth of that.

I then searched for the pictures with comments at the Nasa site.

Here's the most controversial one: http://saturn.jpl.nasa.gov/photos/raw/r ... geID=76730
It was taken pointed to Tethys at approximately 509,689 kilometers away.

The "previous" image is: http://saturn.jpl.nasa.gov/photos/raw/r ... geID=76731
This one was taken pointed to Tethys at approximately 508,727 kilometers away.

Hence, the difference in distance between the images is 962 kilometers. Whatever is seen on the first image is already past in the second (or maybe the other way round). In any case, the object is not very large, as the first image shows it in full, but not with much detail, while the latter one does not show it at all. If it were large, we would expect to see a detailed view of it, especially as the background stars are the same and hence the field of view has not changed. Besides, the object is almost straight ahead, so it should not have gone out of the field of view if it were large.

The third image which is shown first on that website is: http://saturn.jpl.nasa.gov/photos/raw/r ... geID=77038
This one was taken pointed to Tethys at approximately 508,065 kilometers away, a difference of 662 kilometers.

NASA seems to number the images in apparently random order, maybe in the order that they were processed. Thus, we have no way of knowing about the order of that the images were taken. However, the distance from Tethys, as stated on the image comments, gives two possible orders, depending on whether the probe was approaching Tethys or receding from it. The order could be the same as shown on the website - or the opposite of it.

These images were taken probably within a few minutes, depending on the speed of the spacecraft at the time.

The space is a hostile environment, and what applies to photography on Earth does not always apply to photography in space. First of all, as we are dealing with an electronic sensor, many kinds of disturbances can affect the results. Cosmic rays can produce random dots in images, even on Earth. Without the attenuation of the earthly atmosphere, the effect is much more pronounced. This is why any new celestial findings always require at least two separate photographs, to rule out random particle interference.

The image in question, however, does not seem like it was produced by a single cosmic particle. The shape is not round or elliptic, and it does have a curious black part inside as well as graduated upper left side. In space, it is hard to judge distances, but based on that upper left graduation and the general blurriness, I would be tempted to say that the object was very close to the camera. That, in turn, means that the object was quite small, with a probable size in a range of a few centimeters to a few meters. Blurriness could be a result from the object being too close to the telescope, meaning it is not in focus. The shape seen could be a result of the shape of the object and the black part could be a part of the object that is in (its own) shadow.

As Cassini was flying near Saturn, I would guess that it was a stray particle from the Ring. This is consistent with its high reflectivity (a lot of the Ring is made of ice particles).


Top
 Profile Send private message  
Reply with quote  
PostPosted:  
Offline

Joined: Tue Apr 05, 2011 11:52 am +0000
Posts: 92
Additional comment:

I am pretty certain that the narrow field camera was used in this image, because it was taken of a far away object which is still quite small. http://saturn.jpl.nasa.gov/spacecraft/c ... ssdetails/ says that the focal length of that instrument is 2000 mm with a focal ratio of 10.5. Using the other parameters from the page says that the hyperfocal distance of such an instrument is 31.7 kilometers.

Hyperfocal distance means that if an instrument is focused to it, it will produce sharp images upto infinity. However, an astrophysical instrument is certainly focused to infinity, because all of its targets are there. This basically means that between zero and the hyperfocal distance objects are no longer sharp. Looking at the unsharpness the object, I'd estimate it must be nearer than one fourth of the hyperfocal distance, i.e. at 7.9 kilometers.

Using the field of view (0.35 degrees) and estimating that the object takes 60% of the height of the image, the absolute maximum size of it is 58 meters - and probably a lot less. That does not sound like an interstellar base ship.

For the wide field camera, the hyperfocal distance would have been 951 meters. One fourth of it is 238 meters, which would mean that the maximum size of the object would be 17 meters. Hence, even less probable for the object in question.

Besides, bright objects get enlarged in images taken with digital cameras. So in all probability the object is still smaller than its image shows.

My conclusion: whether such an interstellar base station exists or not, this photo is not showing it.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 32 posts ]  Go to page Previous  1, 2, 3

All times are UTC - 7 hours


Who is online

Registered users: No registered users


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You can post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group