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I agreeImaging telescope or lens:CELESTRON EdgeHD 800
Imaging camera:ZWO ASI1600MM-Cool
Mount:Orion Atlas Pro AZ/EQ-G
Guiding telescope or lens:CELESTRON EdgeHD 800
Guiding camera:ASI120MM
Focal reducer:Celestron 0.7x Focal Reducer
Software:Main Sequence Software Sequence Generator Pro, Adobe Photoshop, PHD 2
Filters:Astronomik ProPlanet 742 IR-pass 1.25", Astronomik OIII 6nm CCD 1.25", Astronomik SII 6nm CCD 1.25", Astronomik H-alpha 6nm CCD 1.25"
Accessories:Moonlite CHL 2.5" Large Format Crayford Edge Focuser, Orion Thin Off-Axis Guider (TOAG)
Resolution: 4656x3520
Dates:July 27, 2018, July 28, 2018, July 29, 2018, July 31, 2018, Aug. 9, 2018, Aug. 23, 2018, Aug. 24, 2018, Sept. 5, 2018, Sept. 12, 2018, Sept. 13, 2018, Sept. 17, 2018, Sept. 18, 2018, Sept. 20, 2018, Sept. 21, 2018, Sept. 22, 2018, Sept. 23, 2018
Frames:
Astronomik H-alpha 6nm CCD 1.25": 184x240" (gain: 139.00) -20C bin 1x1
Astronomik OIII 6nm CCD 1.25": 118x240" (gain: 139.00) -20C bin 1x1
Astronomik ProPlanet 742 IR-pass 1.25": 77x240" (gain: 139.00) -20C bin 1x1
Astronomik SII 6nm CCD 1.25": 127x240" (gain: 139.00) -20C bin 1x1
Integration: 33.7 hours
Darks: ~50
Flats: ~50
Bias: ~256
Avg. Moon age: 13.28 days
Avg. Moon phase: 69.38%
Bortle Dark-Sky Scale: 5.00
Astrometry.net job: 2337001
RA center: 13.291 degrees
DEC center: 56.620 degrees
Pixel scale: 0.525 arcsec/pixel
Orientation: 90.794 degrees
Field radius: 0.426 degrees
Data source: Backyard
The Pacman Nebula, NGC281, is an emission nebula about 10,000 light years away in the constellation of Cassiopeia. The nickname is due to its wide-field resemblance to the Pacman video game character. Though, high magnification and deeper exposures tend to wash that resemblance away. The nebula is home to many Bok globule dust clouds which are likely still forming stars.
While it took me a good while to circle back around to processing this image, I was able to combine all the data I collected on it. In total, the integration topped 33 hours. I think many astrophotographers would immediately notice this looks a bit different than a standard "Hubble Palette" SHO mix. The twist here was the inclusion of near infrared (NIR) data. The NIR was shot through an Astronomik IR pass filter designed for planetary use. The filter cuts on at 742nm. Since modern CMOS astro cameras only have limited sensitivity to IR wavelengths, it really took narrowband style exposures to bring the signal out. Still, this channel was the weakest of the four used in the image.
The color mix:
Red: NIR, SII
Green: Ha
Blue: OIII
The final mix was color shifted a bit to remove the predominant green cast. I was pleased to see that NIR did show some reddish nebulosity in areas not usually seen in this nebula. It worked! :) Interestingly, the brightest of these spots is within a major dust lane of the nebula. I can only suppose that there are some concealed stars behind this dust, but that is only a guess. It also contributed to the purple tones in the core of the nebula.
Enjoy a different spin on a common target.
| Cloudy Nights |
| ZWO ASI1600MM/QHY163M |
| Schmidt-Cassegrain Telescope (SCT) Imagers |
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