don-goldman-europe2001narrowband
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Don Goldman, Ph.D. Astrodon Imaging May, 2011 www.astrodonimaging.com Sierra-Remote Observatories • Bisque Paramount ME (MKS400) • RCOS 14.5” Classical Cassegrain Truss, PIR/TCC,Apogee U16M/CFW, Astrodon MonsterMOAG, ST-402 • AP130, Apogee U16M/CFW, RoboFocus • Bisque Paramount ME (MKS400) • RCOS 16” RC tube, Apogee U16M/CFW, PIR/TCC, Astrodon MonsterMOAG, ST-402 guider • FSQ106N, MonsterMOAG, SBIG Remote Guide Head, STL11000/FW8, RobofocusTRANSCRIPT
Narrowband CCD Imaging
Don Goldman, Ph.D.Astrodon Imaging
May, 2011
www.astrodonimaging.com
EquipmentSierra-Remote Observatories
• Bisque Paramount ME (MKS400)• RCOS 16” RC tube, Apogee U16M/CFW,
PIR/TCC, Astrodon MonsterMOAG, ST-402 guider
• FSQ106N, MonsterMOAG, SBIG Remote Guide Head, STL11000/FW8, Robofocus
• Bisque Paramount ME (MKS400)• RCOS 14.5” Classical Cassegrain
Truss, PIR/TCC,ApogeeU16M/CFW, Astrodon MonsterMOAG, ST-402
• AP130, Apogee U16M/CFW, RoboFocus
Topics• What is narrowband imaging?
• Benefits• Narrowband filters
• Mapped Color Processing Tutorial
M1
Broadband Objects
Emit light over a continuum of wavelengths
GalaxiesNGC253
Star Clusters
47Tuc
ReflectionNebula
NGC1579
Narrowband Objects
Emit light at discrete wavelengths due to ionization from nearby UV sources
EmissionNebula
NGC7822
Planetary Nebula,
Wolf-Rayet Bubbles
Helix
SupernovaRemnants
Vela
Benefits of NB Imaging
• Enhanced structural contrast• Use in light-polluted locations
• Extend use of equipment when moon is up
• Add H-a to LRGB for more structure
• Mapped NB color for Hubble-like images
• Hybrid color NB + RGB stars
NGC3576
Natural Color + Great Detailwith H-a/OIII in PN
PuWe1 MWP1 NGC246
YM16 Abell 31 NGC6164
NB for Extended Halos – M97
Normal 3 nm OIII Combined
What is Narrowband?
Photometric Red Imaging Red H-alpha(UVBRI) (RGB)
H-alpha
Photometric RedImaging Red
OIII H-alpha SII
Bandwidth120 nm80 nm5 nm
Contrast Improvement
Wide Red (Orange)
Narrow Red H-α 9 nm H-α 6 nm H-α 4 nm
3x5min exposures, RCOS 12.5” Ritchey-Crétien, SBIG STL11000XM CCD, Bisque Paramount ME
Crescent Nebula, Wolf-Rayet Bubble in Cygnus, NGC 6888
Enhanced Structure at Hi-Res
Conventional RRGB(courtesy Rob Gendler)
Red = H-αBlue=Green=OIII(Don Goldman)
Crescent Nebula in Cygnus, NGC 6888
Comparison of 3 vs 6 nm OIII
• 20” RC• Full Moon• Background ADU decreased from
5700 to 1800• Gradient gone• Smaller stars• Greater faint detail• Moonlight strongest at OIII
Photometric RedImaging Red
OIII H-alpha SII
H-a Filter Transmission Plot
0102030405060708090
100
640 645 650 655 660 665 670Wavelength, nm
% T
rans
mitt
ance
(I/Io
)
Narrowband Filter
Background ADU count scales with FWHM
FWHM, or bandwidth(controls noise, N, or non-emission signal
For highest S/N(contrast):
1. Highest transmittance
2. Smallest bandwidth
Peak Transmittance(controls Signal, S)
100 photons
93 photons
6 nm
Narrowband Filter Selection• 4.5 - 7 nm FWHM
• All 5 nm is good starting point• Good for most scopes – f/10 to f/3
• Moonlight• More at blue-green OIII (more gradients)• Less for deep red H-a, SII
• Consider narrower OIII (3 nm) to reduce moonlight • Consider 3 nm if you have severe light pollution• Start with H-a first, then add OIII, then SII• Can mix FWHM
• Astrodon 5 nm H-a/SII and 3 nm OIII (my Australian setup)• All Astrodon 3 nm (my Yosemite remote setup)• Personal note – fine detail is AMAZING with 3 nm
• Your budget
3 nm and Fast Optics• Decrease signal
~10-12% at f/2.9• Starting high at
93%T (10% loss still > 80%T)
• Background < ½ of 7 nm filter
• Do not need special upshiftedfilter
• See our research http://www.astrodon.com/Orphan/astrodonfaqnarrowband/
Image courtesy of Cesar Quiroga, QSI540 Epsilon-180, Astrodon 3 nm H-a
Narrowband Processing Tutorial
Melotte15 in The Heart Nebula, IC 1805
Goals• Demonstrate clipping layer mask method• Achieve rich, vibrant colors• Improve color of NB Stars• Add 3-D “feel” to our 2-D data• Multiscale High-Pass Filtering
Color Mapping
• Combining Blue, Green, Red, is obvious– All you need is the weighting
• Dual NB (H-a, OIII) – Supernova remnants, planetary nebula - natural look– B ~ G = OIII, R = H-a
• Tricolor NB (H-a, OIII, SII)– Both SII and H-a are red– Hubble (HST) palette (B = OIII, G = H-a, R = SII) most common– CFHT palette (B = SII, G = OIII, R = H-a)
• NB Weights?
Photometric RedImaging Red
OIII H-alpha SII
NB Color Combine Methods• Assign RGB in Maxim, CCDStack, Image
Plus….– Once weights are used and combined, cannot go back
• Preprocess and merge channels in Photoshop– www.flemingastrophotography.com (Neil Fleming)– Once weights are used and combined, cannot go back
• Clipping Layer Mask– http://old.astrodon.com/oldsite/RectorImageProcessing.pdf (Dr. Travis Rector,
U. Alaska)– http://www.imagingdeepsky.com/Presentations.html (Ken Crawford)– Most flexible– Can change hue, intensity, saturation at any time in the process
Clipping Layer Masks in Photoshop• Each NB (H-a, SII, OIII) layer is
in Screen (projector) mode• Each NB layer has a hue/
saturation layer mask• Each layer mask is “clipped”
only to the NB layer immediately below
• Change hue (color) and intensity for each NB independently at any time in the process
• Can add other clipping layer masks, e.g. curves for each NB
Colors are superimposed in
Screen mode as if 3 projectors were used
Melotte 15 in IC 1875 - Masters
SII 3 nmOIII 3 nmH-a 3 nm
Photoshop ProcessingMapped Color
1. Add H-a, OIII. SII preprocessed, registered 16-bit TIF files and label2. Convert image to RGB3. Create hue/saturation (H/S) adjustment layer for each layer
a) Click colorize in H/S adjustment layerb) Slide saturation to 100%c) Slide Lightness to -50d) Slide Hue to 120 for H-a (Green)e) Slide Hue to 230-240 for OIII (Blue)f) Slide Hue to 360 for SII (Red) g) Right click adjustment layer and select “create clipping layer
mask”4. Select “Screen” blending mode for H-a, SII and OIII image layers (not
layer masks)5. Adjust lightness to taste6. Add curves adjustment adjustment layers as needed
Clipping Layer Mask SII
Repeat for OIIITurn off SII screen layer first to see OIII layer
Complete with H-a
Turn Other Layers On
Adjust SII Overall Intensity• Double click on H/S SII adjustment layer• Change the Lightness from -51 to -42
Add SII Curves Clipping Layer Mask
Add H-a Curves Clipping Layer Mask
If you don’t like it, just turn the curves layer off. Cannot turn off the Hue/ Saturation layer.
Change to “Natural Color”• Many do not like the HST color palette• SII is red• Change (green) H-a Hue to red/magenta
PN in Natural Color with H-a/OIII
• Two OIII layers (G,B), H-a (red/magenta)
PuWe1 MWP1 NGC246
YM16 Abell 31 NGC6164
Add RGB Stars• NB stars are
unattractive• Often have
magenta halos• Remove
magenta halos with Selective Color and then Desaturate
• Add RGB stars as top layer
• Blending mode to Lighten Color
Photoshop Processing Selective High-Pass Filtering
1. Duplicate layer2. Select Filter/Other/High Pass3. Select a pixel scale of ~7 for sharp detail (e.g. tendrils)4. Select a pixel scale of ~35-45 for large scale (e.g. galaxy arms)5. Change the blending mode to overlay (sharper) or soft light6. Adjust opacity to taste7. Select hide-all layer mask from Layers8. Use brush in foreground (white) mode9. Adjust brush size 10.Paint over just the areas you want sharpened avoiding stars11.Collapse and save as single-layer 16-bit TIF for prints12.Save 8-bit 72 dpi JPEG file for posting
High Pass Filtering in Photoshop
Fine High Pass (5-9 pixels) to bring out fine structure (e.g. filaments)
Coarse High Pass for 3-D
Review• What is narrowband imaging• Narrowband filters• Benefits• Mapped color using clipping layer masks• Luminance layer• High pass filtering for 3-D effect• Magenta star cleanup• Adding RGB stars• Questions?
Contact: [email protected]
Thank You!!Clear Skies