Sunday, April 6, 2008
Stereo Technique, general notes
NOTES ABOUT IMAGE SIZE.
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When you process the image, it should be at original resolution or moderately
scaled down.
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After all the processing is done, image has to be scaled down for viewing.
The rule of thumb is, that distance between two images should not be large than distance between eyes.
Large the picture is, the more difficult it is to form a stereo image.
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With the Cross Vision method, the image scale can be somehow large.
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GENERAL NOTES OF THE METHOD USED
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Technique precented here is different, than one I have used for my images.
The reason is, that there is now no need for professional 3D-software.
It has some limitations, but overall the actual results are more or less similar.
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Many astro Enthusiastics have done about similar things before with stereo images.
The main difference from this method is, that methods used usually are not very suitable for complex forms, like nebulas.
They are mainly based on simple methods, where objects are moved linear way to
create pseudo 3D-effect.
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If based on real data from objects, those images can be pretty accurate presentaions of the real phenomens.
The reason I'm interested this kind of thigs is, that this way I can see the "real" nature of the object with my own eyes, and maybe I'm able to reveal some of the hidden beauty of the targets as well
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Stereo image viewing instructions
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PARALLEL VISION ISTRUCTIONS:
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In parallel freeviewing the image for the left eye is on the left and the image for the right eye is on the right. You stare into the screen so that your eyes are aimed (more or less) parallel. As you stare into the screen you will get double vision as each eye sees the L & R images separately. When you are staring in at the right distance the middle two images will overlap and become 3d. The outer two images will remain and will still be 2d.
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CROSS VISION INSTRUCTIONS:
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In cross eye freeviewing the image for the left eye is on the right and the image for the right eye is on the left. You stare at a point about 1/2 way to the screen so that your eye's gaze is crossing at the half way point. Thus the left eye sees the correct image which is on the right. As you cross your eyes the image will go double. When your eyes are crossed the correct amount the middle images will overlap and be in 3d. The two outer images will remain and will be in 2d.
How to do Stereo Image pairs, Step by Step instructions
This is a "step by step" instructions, how to turn your 2D-astro images to 3D-stereo pairs
by using a mainstream software, in this case, PhotoShop.
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NOTE!
This step by step presentation is done by using images for the Parallel Vision method.
If you need the Cross Vision method, just swap Right and Left image to the opposite order.
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STEP 1
Dublicate selected astro image and name them as Left and Right.
After this we will make all the changes to the image "Right.bmp"
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STEP 2
In Step 2 we will separate all the stars to the new layer
and supress all the stars from Background layer
Zoom in the image and select stars by using the "color range" tool
under the "select" menu.
After selection is defined use the "expand selection" command under "Select" menu.
Use radius of 2 pixels.
After that, create a new layer and name it "Stars"
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Now click layer "Stars" with right mouse button and select "Select Layer Transparecy"
After that, select the "Background" layer as a active one and turn off visibility of the "Stars" layer
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Now use command "Minimum" under "Filter/Others" menus.
Use 1 as a radius.
After that run "Dust and Scratches" command under "Filter/Noise" menus.
Use radius 2-3.
There is still some fainter stars visible in the image but we'll teke care of them later.
The image in PS should look somethin like this, whe layer "Stars" is turned off.
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STEP 3
Now is time to add some volume to the image!
We'll do it by using "displacement map" technique in PS.
First duplicate the image "Right" destroy layer "Stars" and turn it to the grayscale image.
(Image/Mode menus and select "Grayscale")
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Add some gausian blur to the grayscale image, in this example I have used
radius 5, but you might need to do some experiments.
Blur is used here, becouse we do not want to add "3D-noise" to the
image, sometimes it can work as an effect tough.
After that, save the image as "DisMap.psd", note it has to be in PSD-format!
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Under the "Filters" menu select "Distort" and there pick the command "Displace"
In control window, select "Stretch to fit" and "Repeat Edge Pixels" put "Vertical Scale" to 0
and the "Horizontal Scale" to, lets say, 5.
The Horizontal value has direct influence how strong
the 3D-appearance will be, it's very easy to overdo, so you might need to do some experiments.
Clic OK.
Filter then ask you to pick up the "Displacement Map", use one you created in previous step.
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STEP 4
After step 3, we have a "Raw" stereo pair image. You can now see how it looks!
If the effect is too strong or weak, just go back few setps and adjust values in Displacement
menu.
As you can see, there is allready 3D-appearance in image.
Stars are still "flat" and the object is "glued" to the background.
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First we handle the object.
Select the main object loosly with the "Lasso" tool,
and add some "feather" to the selection, value 12 is used here.
Turn the selection to the new layer, name it as "Object1".
(Here is just one main object, but there can be several of them)
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After that we can modify the objet's location in Z-axil and allso its "tilt"
in the space.
In this case, moving objet to the Left moves it closer the viewer and moving it to the Right
moves it deeper in image.
You can control it by moving object with the arrow buttons while looking the object as stereo
at the same time.
To changes object "tilt" in Z-axel we use "Transform" commands under the "edit" menu.
Select command "Distor" and skew the image as seen in picture above. You should stil look
the image pair as a stero at the same time to see the effect.
Remember again, it's very easy to overdo it.
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STEP 5
Now we have the object located as we want it to be.
In this step we will take care of stars.
We want that stars are frorming a volume, not a plane.
If there is juts few stars, we can move them manually with same manner as we moved the main
object.
But if there is hundrets of stars it's too much work to move them one by one.
We have all the brighter stars allready in separate layer, now we just have to select them with
"random" manner to be able to build a realistic volume.
First we will create a "selection map" for the stars.
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Duplicate the image, flattent the layers, fill it with neutral gray and scale it down 25%.
Select command "Noise" under the "Filter" menu.
Under the "Noise" selct command "Add Noise"
Use values as seen in the image above.
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Scale image up 400% by using "Nearest Neighbor" method under the "Image Size" menu.
Use command "Color Range" under the "Select" menu to select lighter pixels
in crated Noise image.
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After that move the created selection to the "Rigt" image and use command "create a New Layer by Cut"
You can now use the same selection, rotated and/or scaled, to create more new layers with
separated stars.
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Now we can move star layers smal amount to the different directions, and create
some smooth volume to the star field.
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There is still many very faint stars at image backgound, we can use same method to them
as above. The object is in separate layer, so it will stay unharmed.
Use even more delecate movements for background stars.
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NOTE!
Use very small movements at first, you will easily destroy the stereo effect with
too strong movements.
Brighter, separate stars can be moved manually, use clone tool to move stars
and erase original. (We can assume, that very bright stars are closer than dim ones)
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NOTE 2!
For more realistic look you can divide stars to different layers by using the star brightness as a selection criteria. You can use "Select Color Range" command together with gaussian blur to
make selection as accurate as possible. More layers you use , more accurate is the result.
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STEP 6
We have created a image pair for the Parallel Vision.
To create one for the Cross vision we just swap the images horizontaly.
The image pair for the Cross vision
Friday, April 4, 2008
The Great Sh2-240 as a Stereo pair
Image pair for Parallel Vision
Image pair for Cross Vision
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I made this stereo pair again.
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I have improved my method even more accurate.
The 3D impression is "realistic" vision of the object as it is a
3d structure floating in the space.
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This is a artistic visualisation of the object, not the accurate presentation of real distances.
How ever, I have based distance information to different kind of data, that can be read out
of the original RAW-image data.
For example, star magnitude is used to determine star levels in 3D-image.
In nebula area of image I have used level of gray to determinite its location in Z-axel, but with nonlinear manner.
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As usual, there is two versions.
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One for parallel vision, and the other one for cross vision method.
Thats becouce some part of the viewers can see one of the method in 3D, but not
the other. (I can't see cross vision images)
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PARALLEL VISION ISTRUCTIONS:
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In parallel freeviewing the image for the left eye is on the left and the image for the right eye is on the right. You stare into the screen so that your eyes are aimed (more or less) parallel. As you stare into the screen you will get double vision as each eye sees the L & R images separately. When you are staring in at the right distance the middle two images will overlap and become 3d. The outer two images will remain and will still be 2d.
-
CROSS VISION INSTRUCTIONS:
-
In cross eye freeviewing the image for the left eye is on the right and the image for the right eye is on the left. You stare at a point about 1/2 way to the screen so that your eye's gaze is crossing at the half way point. Thus the left eye sees the correct image which is on the right. As you cross your eyes the image will go double. When your eyes are crossed the correct amount the middle images will overlap and be in 3d. The two outer images will remain and will be in 2d.
Thursday, April 3, 2008
NGC 2903
NGC 2903 is a barred spiral galaxy about 21 million light-years away
in constellation Leo.
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IMAGING DETAILS
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Optics: Meade LX200 GPS 12" @ f6.3
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Camera: QHY8
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guiding: SXV-AO, active optics unit and LodeStar guider @ 11Hz
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Exposures: 9 x 1200s+ Flats and Bias frames, no darks total exposure time 2h 15min.
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Filter: IDAS LP
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UPDATE,
There was color channel error in the image.
Now colors are correct.
Wednesday, April 2, 2008
NGC 4565
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This beautiful edge-on galaxy, in constellation Coma Berenices, has a unbarred spiral structure.
Distance from our home planet is about 53 milijon light-years.
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Transparency was poor, but seeing better than usually in my location.
Result from that, is tighter stars and some details can be seen in the galaxy disc.
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IMAGING DETAILS
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Optics:
Meade LX200 GPS 12" @ f6.3
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Camera:
QHY8
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guiding:
SXV-AO, active optics unit and LodeStar guider
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Exposures:
8 x 1200s+ Flats and Bias frames, no darks
total exposure time´2h.
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Filter:
IDAS LP
Tuesday, April 1, 2008
New feature, sorting by category
I have added a new feature to the Blog.
On the right hand side, there is a "Posts By Category" list.
It's now more convient to browse older posts.
Saturday, March 29, 2008
Sh2-240 with more photons.
The Sh2-240 (Simeis 147) is a very faint supernova remaint in Taurus.
The image is in false color to show hydrogen alpha emission.
Original BW H-alpha image at the bottom
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This is a huge object, it covers nearly 3 degrees (6 full moons) on the sky.
Estimated distance from my home town Oulu is about
3000 light-years. The width of the object is 160 light-years.
This supernova remnant has an apparent age of about 100.000 years.
(Light from massive explosion reached Earth 100.000 years ago)
In the center of the remaint, there is a fast spinning neutron star or pulsar.
I started this project with, Sh2-240 supernova remant, at march 6. 2008.
So far I have collected lights for this very dim object litle by litle.
I feel like there have been all possible troubles with this object.
Number one, weather... like to say word or two but I hold back.
Number two, mechanical problems with guiding and only with this object!
Number three, bad flats, there is something seriously wrong with my flat frame box.
(I'll make a new one by using EL-panel!)
And many more troubles, only about one of three light frames was usable
doe the thin upper clouds.
They are allmoust impossible to spot from my location. Normally so thin clouds does not do too much harm. In this case the target has so low surfage brightness, that even slight
variations in transparency distroy the image.
The effect of bad trancparency is possible to spot during processing, so lots of work for nothing has been done here.
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IMAGING DETAILS
Optics:
Canon FD 200mm f2.8 lens with full aperature
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Camera:
QHY8
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Platform and guiding:
LX200 GPS 12" with QHY5 guider and PHD-guiding
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Exposures:
10 x 3600s + 4 x 2700s + 3 x 900s H-alpha + Flats and Bias frames, no darks
exposure time so far 13h 45min.
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Filter:
Baader 7nm H-alp + IDAS LP for RGB
Hydroge alpha channel only
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Update:
I reprocessed images, and I was able to go litle deeper, I think.
The data is yet "thin" and more exposures are needed, maybe an other ten hours.
Friday, March 28, 2008
Sh2-129
Sh2-129 is a very dimm diffused H-alpha nebula in the constellation of Cepheus.
The nebula is situated about 4 degrees west from IC 1396.
I made a small mosaic to show the actual location compared to IC 1396.
IC 1396 image is from 24.03.2008 and can be seen alone in previous post.
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IMAGING DETAILS
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Optics:
Canon FD 200mm f2.8 lens with full aperature
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Camera:
QHY8
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Platform and guiding:
LX200 GPS 12" with QHY5 guider and PHD-guiding
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Exposures:
6 x 1800s H-alpha +4 x 600s RGB + Flats and Bias frames, no darks
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Filter:
Baader 7nm H-alp + IDAS LP for RGB
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