Imaging telescopes or lenses: Takahashi FSQ106 EDX4
Imaging cameras: FLI ML-16070M
Mounts: Software Bisque Paramount MyT
Guiding telescopes or lenses: Stellarvue F50
Guiding cameras: ZWO ASI174mm Mini
Focal reducers: Takahashi 645 QE 0.72x Reducer for FSQ106
Software: Sequence Generator Pro V3.0 · Photoshop CC · Starnet ++ · PixInsight Processing Software · Open PHD Guiding PHD2 Guiding · The SkyX
Filters: Astrodon Hα 50mm round 5nm · Astrodon B 50mm square E Series · Astrodon G 50mm square E Series · Astrodon R 50mm square E Series · Astrodon O-III 50mm square 3nm · Astrodon S-II 50mm Square 3nm
Accessory: Optec Gemini Focusing Rotator
Dates:Jan. 13, 2021
Frames:
Astrodon B 50mm square E Series: 37x60" -25C bin 1x1
Astrodon G 50mm square E Series: 37x60" -25C bin 1x1
Astrodon Hα 50mm round 5nm: 52x1800" -25C bin 1x1
Astrodon O-III 50mm square 3nm: 50x1800" -25C bin 1x1
Astrodon R 50mm square E Series: 38x60" -25C bin 1x1
Astrodon S-II 50mm Square 3nm: 46x1800" -25C bin 1x1
Integration: 75.9 hours
Darks: ~23
Flats: ~25
Bias: ~50
Avg. Moon age: 0.32 days
Avg. Moon phase: 0.12%
Astrometry.net job: 4271813
RA center: 7h 0' 41"
DEC center: -3° 49' 37"
Pixel scale: 4.894 arcsec/pixel
Orientation: 0.135 degrees
Field radius: 3.132 degrees
Resolution: 3840x2556
Locations: Sierra Remote Observatories, Auberry, CA, United States
Data source: Own remote observatory
Remote source: Sierra Remote Observatories
Data Acquisition from 2020-10-17 until 2021-01-13
DSO Color Mapping: SH-HO-O with RGB stars
Original Image (Pix) Scale: 4.00
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I believe this is the first successful color image of the nebulae Sivan 5 and Sivan 6. Siv 5 is the larger one at the top. Siv 6 lies beneath it and includes Sh2-287, the bright section bottom center. The swooping HII wisp that stretches from left to right and looks like a ship’s hull isn’t officially part of either nebula, and is probably just part of the interstellar medium.
Astronomer J.P. Sivan and his associates identified these nebulae in 1974 from an Hα survey of the Milky Way in which they appeared as a couple of tiny, irregular blots. Apparently, no one has bothered with them since.
Sivan Nebulae are large and exceedingly faint: this image spans over 5° of the constellation Monoceros and uses 74 hours of narrowband data. For 74 hours I got good Hα, adequate SII, and faint but usable OIII. The shorter exposures I’ve seen of this region scarcely reveal these Sivan objects at all. Even the three Sharpless objects here barely appear. If you find any images that clearly show these Sivan nebulae, please let me know and I will update this page.
As this is a potential first, I wanted to keep the colors close to true. This is an SH-HO-O treatment with only a little of the Hα in the green channel. The stars are RGB.
...Speaking of blots, in the cosmic Rorschach ink blot test that is interstellar space, to me this looks like a dog (or seal) sitting in a boat with a single sail. So, I call this the Seadog Nebula.
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