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Phys 1830 Lecture 18
Second Term Test is coming
up Friday Mar 6.
Covers material after previous
test (pseudo-cummulative).
Topics from “how images are
made” (lecture 11) through
“computer simulations”
(coming up).
Check material online for test
information.
Opportunities to study:
Monday : AstroClub
Allen 330? at 3pm
Wed Allen 330 at 5:30pm
Office hour: Monday
Allen 514 at 3pm
Upcoming Classes
• Visualization:
– Workshop
– Computer Simulations
• Planetary Systems
– Formation
– Simulations
– Observations
• Our Solar System
• Solar System Formation
Quiz
Phys 1830: Lecture 18
Bubble Nebula – NGC 7635
summary
Recall column
• Goal: Explore how to construct
a public outreach image.
• Within each public outreach
image is the struggle between
scientific meaning and visual
aesthetic.
Summary:
Recall column
summary
• Composition Considerations:
– Lead the eye to keep it in the
picture plane.
– Create a foreground, middleground, and background.
– Consider how the image will be
read in terms of temperature, etc.
• Colour Considerations:
– Harmonious colours work with the
viewers’ physiology.
– Optical effects can be used to help
explain the science.
– There are 7 colour contrasts.
Simple Colour Wheels
B is called blue but is purple
(i.e. blue-violet)
R is called red but is orange
(i.e. red-orange)
Goal:
Select colours to make a harmonious final image.
That is, generate a final image with
complementary colours, greys (not browns), at
least one of the 7 contrasts, etc.
Seven Colour Contrasts
Which of these contrasts interest you and your partners?
Seven Colour Contrasts
Fire up GIMP! (Take Notes!)
1. Setup layer file (.xcf)
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Make new file with black background
Copy thumbnails into layers with screen mode
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Copy visible, paste, name, set mode = screen.
black background layer helps reduce noise.
2. Colourize each layer
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Copy layer, turn off original
Use levels tool to select colour in active layer
colour need not be what your eye would see; consider
aesthetics and visual grammar.
3. Adjust colours
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Curve tool
helps reduce noise, increase detail and harmony.
Fire up GIMP!
4. Create single layer file (.tiff)
– Make new file with black background
– Copy visible from .xcf file and anchor, flatten.
5. Adjust colours
– Curve tool
– generate striking images
6. Orient
7. Crop
• both 7 & 8 guide the eye.
8. Cosmetics (remove cosmic rays & noise)
If you are ahead of the class, do a different colour rendition! See if it works better.
Cosmetics
• make unresolved sources white
(layer in a stretched B&W image)
• remove CRs and chip seams in optical images
(clone tool)
Critique --MONDAY
When finished on MONDAY send an email with 3 items
1. Send your jpg images to
[email protected] for the website and
for grading.
2. Include the full names and student numbers of
everyone on your team
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state their attendance for each day (if in attendance it
will be assumed that they participated).
3. BRIEFLY state the following in your email:
• what were your final colours
• what were your final contrasts
• did your image have an appropriate vertical or diagonal element to
retain the viewer’s attention
• how do your results compare to your goals?
Lesson 1
• The process of making astronomy images is
iterative. Sometimes one has to go right back
to the stretching.
Lesson 2
• More than one colourization, orientation, etc
is valid.
Compare with other versions:
http://www.physics.umanitoba.ca/~english/vizimagesUVi
c/
http://www.physics.umanitoba.ca/~english/2013fallphys1
830/bwimaging/imagesindex.html
Examples of various versions of a
nebula in optical exercise
The following slides show that there is not ONE
right way to colourize and present an image -there are many valid renditions.
summary
Compare Your Images:
Recall column
The Veil Nebula: Mortfield & Cancelli
Far
Close
• We saw the Veil Nebula when we did
surface brightness.
• This is made by serious amateur
astronomers using just hydrogen and
oxygen.
Compare with Hubble Heritage Team
Recall column
summary