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The tadpole galaxy: HST data processed with
PixInsight
Mehdi Bozzo-Rey, [email protected]
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About the tadpole galaxy● Other “names” :
○ UGC 10214- Uppsala General Catalog of Galaxies (12921 galaxies - northern hemisphere)○ Arp 188 - Atlas of Peculiar Galaxies, produced by Alton Arp (338 galaxies)○ PGC 57129 - Catalog of principal galaxies (73 197 galaxies)
● Distance: 420 million light years● redshift: z=0.031358
Mehdi Bozzo-Rey: [email protected]
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about the tadpole galaxy - spitzer (Infrared)
Mehdi Bozzo-Rey: [email protected]
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Redshift and the police car● Doppler effect:
○ when the police car comes towards you at high speed : increased pitch (high frequency, which means shorter wavelength)
○ after the police car passes by : decrease in pitch (lower frequency, which means higher values for the wavelength)
● Sound and light : both waves, the same process applies● for the light: shorter wavelength = blue shift, if the wavelength has higher
values = red shift● If an object goes away from you: redshift. If it is going towards you: blueshift
Mehdi Bozzo-Rey: [email protected]
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What can you do when you know the redshift ?● You can calculate how fast a galaxy is moving away from you !● When z is small compared to 1 (which is our case) the velocity of the galaxy is
given by : v=c z, where c is the speed of light● v = 300 000 * 0.031358 = 9407 km/s !
Mehdi Bozzo-Rey: [email protected]
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How old is that picture, anyway ?● Distances in astronomy always relate to time as light travels at a finite speed
(300 000 km/s)● 425 Mly means … the light the HST caught left the galaxy before … we even
had dinosaurs on earth !
Mehdi Bozzo-Rey: [email protected]
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425 Mly … Silurian
Mehdi Bozzo-Rey: [email protected]
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425 Mly … arthropods
Mehdi Bozzo-Rey: [email protected]
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tadpole galaxy: how to get the data (1)
Mehdi Bozzo-Rey: [email protected]
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tadpole galaxy: how to get the data (2)
Mehdi Bozzo-Rey: [email protected]
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One last word about PixInsight and image processing From the PixInsight forum:
Mehdi Bozzo-Rey: [email protected]
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PixInsight : loading the data
Mehdi Bozzo-Rey: [email protected]
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STF - Autostretch
Mehdi Bozzo-Rey: [email protected]
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dynamic crop
Mehdi Bozzo-Rey: [email protected]
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STF - autostretch again
Mehdi Bozzo-Rey: [email protected]
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DBE - sample generation
Mehdi Bozzo-Rey: [email protected]
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DBE : tolerance
Mehdi Bozzo-Rey: [email protected]
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DBE: sample weight
Mehdi Bozzo-Rey: [email protected]
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DBE: not in background
Mehdi Bozzo-Rey: [email protected]
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DBE: image correction
Mehdi Bozzo-Rey: [email protected]
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DBE: extracted background
Mehdi Bozzo-Rey: [email protected]
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DBE: before / after
Mehdi Bozzo-Rey: [email protected]
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background neutralization: preview
Mehdi Bozzo-Rey: [email protected]
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background neutralization: using the preview as ROI
Mehdi Bozzo-Rey: [email protected]
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color calibration
Mehdi Bozzo-Rey: [email protected]
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autostretch again (unlink channels)
Mehdi Bozzo-Rey: [email protected]
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sampleformat conversion: convert to 64bit image
Mehdi Bozzo-Rey: [email protected]
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save STF process
Mehdi Bozzo-Rey: [email protected]
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rename STF icon
Mehdi Bozzo-Rey: [email protected]
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reinject STF process in histogram transformation (1)
Mehdi Bozzo-Rey: [email protected]
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reinject STF process in histogram transformation (2)
Mehdi Bozzo-Rey: [email protected]
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apply histogram transformation and disable stf (F12)
Mehdi Bozzo-Rey: [email protected]
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masks: luminance or lightness ? (1)Extracting lightness
Mehdi Bozzo-Rey: [email protected]
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masks: luminance or lightness ? (2)extracting luminance
Mehdi Bozzo-Rey: [email protected]
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masks: luminance or lightness ? (3)luminance vs lightness
Mehdi Bozzo-Rey: [email protected]
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Things to remember when creating masks● We need at least 2 masks: one for the structure, one for the background● What is black will stop the process from being executed in this area● What is white acts as an open window in front of the picture: the
process/transformation will be executed in this area● There are multiple ways of building masks, channel extraction for luminance /
lightness with histogram transformations is the easiest way● You may need more than 2 masks in order to achieve the best results !
Mehdi Bozzo-Rey: [email protected]
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clone luminance, invert and rename
Mehdi Bozzo-Rey: [email protected]
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histogram transformation - luminance mask
Mehdi Bozzo-Rey: [email protected]
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histogram transformation - inverted luminance mask
Mehdi Bozzo-Rey: [email protected]
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HDR multiscale transform - luminance mask
Mehdi Bozzo-Rey: [email protected]
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HDR multiscale transform - final
Mehdi Bozzo-Rey: [email protected]
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what happened ??? - tip of the day● if you apply a mask and then duplicate a preview, the mask is lost ! It is
equivalent to applying your process on the preview, using a white mask (i.e. no mask) the size of the preview
● the right way to test is to apply the transformation on the preview and then reset the preview (you can duplicate the transformed preview in order to “save” it)
● conclusion: we need a new mask :-)● The idea is that the original mask is “not white enough” for the core of the
galaxy
Mehdi Bozzo-Rey: [email protected]
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luminance “core” mask
Mehdi Bozzo-Rey: [email protected]
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HDR using our new “core” mask
Mehdi Bozzo-Rey: [email protected]
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you can play with the masks ...
Mehdi Bozzo-Rey: [email protected]
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curves transformation - inverted lum mask - readout
Mehdi Bozzo-Rey: [email protected]
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curves transformation - background final
Mehdi Bozzo-Rey: [email protected]
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curves transformation - core
Mehdi Bozzo-Rey: [email protected]
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Noise reduction:ACDNR - background - previews (1)
Mehdi Bozzo-Rey: [email protected]
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Noise reduction:ACDNR - background - previews (2)
Mehdi Bozzo-Rey: [email protected]
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ACDNR - background - full image
Mehdi Bozzo-Rey: [email protected]
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ACDNR - core- luminance mask (not lum_core)
Mehdi Bozzo-Rey: [email protected]
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color saturation - luminance mask
Mehdi Bozzo-Rey: [email protected]
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Histogram transformation - luminance mask
Mehdi Bozzo-Rey: [email protected]
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curves transformation - luminance mask - blue boost
Mehdi Bozzo-Rey: [email protected]
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the tadpole galaxy published by NASA
Mehdi Bozzo-Rey: [email protected]
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Our tadpole galaxy
Mehdi Bozzo-Rey: [email protected]
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details - NASA
Mehdi Bozzo-Rey: [email protected]
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Our tadpole core
Mehdi Bozzo-Rey: [email protected]
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saving the final image
Mehdi Bozzo-Rey: [email protected]