From: "Tim" <tjp314@pacbell.net>

Date: May 1, 2008 6:12:44 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Moon Anaglyph


Alberto:


When I tried to open that file, I got a "file not found" message, so I

haven't seen it.


I'm a geologist, and work with stereo orbiter images of Mars all the

time.  20 years ago, all we had was Viking Orbiter, which was seldom

intentionally stereo (except for landing site selection for the Viking

Landers), so the parallax is all over the place.  But The Viking

orbiters did acquire enough data such that there is a fair amount of

stereo over much of the planet, at least at regional scales.  Most of

the pairs listed as "useable" for stereo viewing of topography have

parallax or separation angles on the order of several degrees to 45

degrees (or even more).  In my experience, separation angles of at

least 15 degrees were necessary to see much topography, particularly

in plains regions.


The HiRISE camera team on the Mars Reconnaissance Orbiter mission does

targeted stereo of areas of high scientific interest and landing

sites.  To get the conjugate image, the spacecraft has to be rolled

off nadir, so they often have to "take what they can", but they

typically try to acquire stereo pairs with a separation angle of about

20 degrees.


-Tim.

--- In Astro_IIDC@yahoogroups.com, "richter1956" <richter1956@...> wrote:


Tim,

2 degrees are a normal working condition for our eyes.

Looking at an object 2 meters far from our eyes we have a 2 degree

separation 

angle.(depending on the distance between the eyes)

You surely agree that at 2 meters far we still perceive a strong 3D

effect... but at 4 meters 

too (1 degreee).


Of course our brain can process even bigger angles with stronger 3d

effect, but 2 degrees 

are considered as the base-rule for the 3d vision (distance between

cameras= 1/30 of the 

distance from the object).


Did you check the test  image i uploaded  with red/cyan glasses?

The 3D Moon roundness is perfectly detectable.


I guess that our eyes/brain can help more than expected.


The  3D perception through stereograms (later through

autostereograms too)  

demonstrated also that 3D synthesis is not influenced by  the  main

subject of the image.

The 3D perception is a direct brain synthesis based on viewing

difference  and happens 

even with a meaningless  random series of dots or patterns 

represented in the image.


http://www.makina.it/Shuttle-Autostereo.jpg


Anyway do exist an easier 3rd option: no libration, no spaceflight

but simply connect an air 

compressor to some old unused oil pipe going deep in the ground, and

inflate the Earth 

until the necessary diameter is reached!


regards


Alberto







--- In Astro_IIDC@yahoogroups.com, "Tim" <tjp314@> wrote:


A few degrees isn't enough of a baseline for stereo viewing.  You'd

need libration (or leaving the Earth!) to get more.  


-Tim.


--- In Astro_IIDC@yahoogroups.com, "richter1956" <richter1956@> wrote:


Hi Jeff,

i know the other possibilities for 3D imaging of the Moon.

The one i choose is the easier for a single person / single night 

because it is not so 

difficult to get some image approx 3 hours before and 3 hours after

the meridian (4 hours 

could be even  better of course).

In this case we could get approx 1° of difference.

That is not much (2° could be better) but enough to get some 3d

effect.


Did you check with 3d glasses the image i uploaded into the Lunar

section?

The sphere shape could be easily detected.


The limit of this method is the NON.realtime imaging like the

simultaneous photos do,

Another little problem is caused by the terminator and the shadows

that move a little 

within the 6 hours interval.


Anyway i like this kind of imaging not for scientific purposes but

for the emotional impact 

caused by the 3D view.


If that method will work even on detailed images, like the Alan

Friedman ones, then we 

could dream to fly with an Apollo mission :-)


Regards


Alberto




--- In Astro_IIDC@yahoogroups.com, Jeff Phillips <imjeffp@> wrote:


I was involved briefly with a Luna 3D project a couple of

years ago  

where we were trying to coordinate photographers in both

hemispheres  

to make simultaneous photos of a feature, using the Earth's

diameter  

as a baseline. IIRC, we were never able to coordinate dates and

weather.


The other problem was that the eastern photographer had to shoot  

early in the morning.  If I were going to try again, I'd try to  

coordinate two cameras, one in S. Africa and the other in

eastern  

Europe (around 20°E for both, 30°S & 50°N).


One thing to try for a single observer would be to use

libration to  

create your baseline. I'd need to do more research to

determine two  

nights with the moon at the same age (within several hours at

least)  

and opposite librations (if that's the word).


On Apr 28, 2008, at 12:05 PM, Alan Friedman wrote:


Hi Alberto,



Thanks for the interesting project idea.


I am afraid if I ever experienced six hours of good seeing,

I will  

be flying with a harp in heaven! But I will keep it in mind

should  

I encounter such a fine night on earth.


best wishes,

Alan



On Apr 28, 2008, at 6:26 AM, richter1956 wrote:


Hello to all,


i recently added 2 files in the Lunar section.


One of them is an anaglyph to be watched with red/cyan 3D

glasses:




Anaglyph-SouthPole 3000x2000.jpg






I! 'm wondering about doing some anaglyph starting from

high-end  

quality images like Alan Friedman ones... :-)


Maybe Alan could kindly take a wonderful detail (like the  

delicious Plato or Copernicus i can see on his site ) 3 hours  

before the meridian transit and 3 hours after that  

transit....pleeease!!


I guess  that 6 hours-difference  could be enough to reveal

the  

internal 3d structures of the craters but i'm not sure of that.


The sine-qua-non condition is to have the very best image

quality  

and the most similar settings (exposure, contrast etc) for

the 2  

images.




I attempted to get single craters images but my quality was

not  

enough even because i found bad seeing in almost one of the 2  

shots (yes you need 6 hours of good seeing).






The other file added is a Moon mosaic grabbed with my C8.


I printed a 70x100 cm poster of it:


080214-The Moon 6353 x 4326.jpg






kind regards to all




Alberto




PS: i did some experiment with DMK on well known DSO (M51)

not  

guided: really interesting results.









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