NGC 6946 - Arp 29


Object: NGC 6946, 9.6m, 11.5' x 9.8', SAB(rs)cd spiral galaxy, at a distance of approximately 6.5 Mpc (21 Mly) on the Cygnus-Cepheus border.


Subimages L: 20 x 300 sec (1.7 hrs), Input FWHM = 2.6 - 3.3", Combined FWHM=2.95", Deconvoluted FWHM=2.1"
Subimages RGB: 8 x 300s (0.7 hrs) binned 2x2
Scope: C11XLT EFL=1659 mm (f/6 effective)
Mount: Losmandy G11 with Gemini L4
Camera: ST8XME+CFW10 set to -20C
Guiding: Self-guide, ExpTime=2s, dithered
Acquisition and processing: MaxIm DL/CCD v4.5 and v5
Imaged on: Oct 4, 2007

Processing Log

Lum channel:
Remove Bloom, manually adjusted rectangles
CCDSharp Lucy-Richardson deconvolution, 7 stars selected, 4 iterations
Remove Pedestal, Subtract 1438 from data
DDP, No filter, bgd=90, mid = 600

Blue channel:
Remove Pedestal, 528 ADU
DDP, No filter, bgd=90, mid = 600

Green channel:
Remove Pedestal, 880 ADU
DDP, No filter, bgd=90, mid = 600

Red channel:
Remove Pedestal, 876 ADU
Red channel: DDP, No filter, bgd=90, mid = 600

Color image:
Color Combine, Lab, auto bgd, 1:1.1:1.3
Stretch, From 65K to 255
Color Balance, Bgd:auto, 5% to Blue channel
Clone, Fixed haloes and bloom remnants with Gaussian Blur of r=1.3
Color Balance, Bgd:none, 7% to Blue and green channels

Alternatively Processed


Subimages L: 47 x 300 sec (3.9 hrs)

Lum channel:
Stack SigmaClip with all frames, used astrometric align
Stack SigmaClip with all frames, used astrometric align, auto upsampled x2
Crop 180,30 x 940,940
Crop 180,30 x 940,940
Remove Bloom manually adjusted rectangles and used Clone tool to put some stars back
CCDSharp LR 7 stars selected, 4 iterations
Remove Pedestal Subtract 1175 from data
DDP No filter, bgd=90, mid = 600

Blue channel:
Remove Pedestal 530
DDP No filter, bgd=90, mid = 600

Green channel:
Remove Pedestal 880
DDP No filter, bgd=90, mid = 600

Red channel:
Remove Pedestal 890
DDP No filter, bgd=90, mid = 600

Color image:
Color Combine Lab, 1:1.1:1.3, Lw=100%
Stretch From 65K to 255, gam=0.6, low=3000 high=66190
Clone Fixed haloes and bloom remnants with Gaussian Blur of r=1.3 and some bad pixels
Adjust Sat 125%
Crop 15,15 x 910,910