- Image
centered on: RA 20:50:53 DEC +60:20:45
- Exposure
time: 3 hours, 45 minutes, LRGB = 120:35:35:35 minutes
(15 min. L and 5 min. RGB sub-exposures)
- Lens/telescope: Takahashi FSQ-106ED (4.2")
quadruplet ED refractor at f/3.6
- Image scale: 2.89 arcseconds per
pixel, FOV 160.2' x 120.6' (F = 385 mm at 5.4 micron pixels)
- Camera: SBIG
ST-8300M
(T:
-20 degrees
Celsius) with Astronomik LRGB filters
- Mount: Astro-Physics Mach1 GTO
(guide rate: 1x, PEM activated)
- Guiding: TS
OAG +
SX Lodestar + PHD (small dither, settle
< 0.5)
- SQM: 21.4 magnitude per square
arcsecond
- Location: Etoile St. Cyrice, Hautes-Alpes,
France
- Date: September 1 - 2, 2011
Workflow
Image
acquisition in Nebulosity (v2.4.0):
- Capturing
5 flat frames per channel with a Geoptik
Flat Field Generator
- Capturing
8 L light frames of 15 min. and 7 R, 7
G and 7 B light frames of 5 min. per channel
Pre-processing
in
Nebulosity
(v2.4.0),
Sigma
Beta
10,
Maxim
DL
(v4.56)
and RegiStar
(1.0.7):
- Pre-processing
the
flat
frames
with
a
master
bias
frame
(from
library)
and
stacking
them
(5
per
channel)
at "Average /
Default" in Nebulosity
- Pre-processing
the
light
frames
with
the
stacked
flat
frames
and
a
master
bias
frame
- Subtracting
the
bad
pixels
from
the
pre-processed
light
frames
with
bad
pixel
maps
(from
library)
- Aligning
(registering) the pre-processed, bad
pixels subtracted light frames and saving each individual file
- Stacking
the individually saved registered files
(per channel) with "Standard Deviation Masking" algorithm in Sigma
Beta 10
- Aligning (registering) the colour
channels in RegiStar.
- Combining
the colour channels (RGB ratio 1:1:1.8,
"Bgd Auto Equalize" checked) to create an RGB image in Maxim DL
- Trimming
the dark edges of the L image and RGB
image in Nebulosity
- Applying
the "Digital Development Processing
(DDP)" tool for both the L and the RGB image
- Applying
"Adjust Colour Background
(Offset)" for
the RGB image
- Aligning
the L image to the RGB image in RegiStar and saving the
images as 16-bit TIFF files
Post-processing
in
Photoshop
(CS4)
and Nebulosity
(v2.4.0):
- Placing
the RGB image as a layer on top of the L
image (layer blend mode "Colour") in Photoshop
- Slightly
adjusting
levels on
both
the
L
and
RGB
layer
in order to set thet background brightness to 25:25:25
- Increasing
the colour intensity of the RGB layer
with "Match Colour"
- Iteratively
slightly
adjusting
levels and curves on both the L and RGB to increase
contrast
- Applying
"Hasta La Vista, Green!" on the RGB layer
- Colour
balancing by adjusting contrast on the a and b channels in Lab Colour
mode
- Selective
colour enhancement with "Selective Colour" on the RGB layer
- Sharpening image with "Tighten
Star Edges" (L and RGB layers merged/flattened)
- Applying "Deep
Space Noise Reduction"
action
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