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Contains:  AO Cas, R Cas
Getting plate-solving status, please wait...
Sivan 2 (Siv 2, Siv2), 


            Jeffrey K Lovelace

Imaging telescopes or lenses: Takahashi FSQ-106

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: Photoshop CC  ·  Sequence Generator Pro V3.0  ·  Open PHD Guiding PHD2 Guiding  ·  The SkyX  ·  PixInsight Processing Software

Filters: Astrodon O-III 50mm round 3nm  ·  Astrodon S-II 50mm round 3nm  ·  Astrodon Hα 50mm round 5nm  ·  Astrodon B 50mm round E Series  ·  Astrodon G 50mm round E Series  ·  Astrodon R 50mm round E Series

Accessory: Optec Gemini Focusing Rotator  ·  FLI CFW-2-7 50mm round 7 position filter wheel

Astrodon B 50mm round E Series: 24x120" -25C
Astrodon G 50mm round E Series: 24x120" -25C bin 1x1
Astrodon Hα 50mm round 5nm: 24x1800" -25C bin 1x1
Astrodon O-III 50mm round 3nm: 24x1800" -25C bin 1x1
Astrodon R 50mm round E Series: 24x120" -25C bin 1x1
Astrodon S-II 50mm round 3nm: 24x1800" -25C bin 1x1

Integration: 38.4 hours

Darks: ~25

Flats: ~25

Bias: ~50

Bortle Dark-Sky Scale: 1.00

Mean SQM: 22.00 job: 3824091

RA center: 0h 14' 29"

DEC center: +51° 11' 53"

Pixel scale: 8.057 arcsec/pixel

Orientation: 90.045 degrees

Field radius: 3.227 degrees

Resolution: 1602x2400

Locations: Sierra Remote Observatories, Auberry, CA, United States

Data source: Own remote observatory

Remote source: Sierra Remote Observatories


Data Acquisition from 2019-10-01 until 2019-11-25.
Original Image scale: 4.0 (the submitted image is 0.5 scale)
Narrowband Color: HSO

The first successful narrowband tricolor image of Sivan 2?

Little is known about the nebula Sivan 2 (Siv 2) beyond it lying approximately 1380 parsecs (4500 light years) away and being an HII region. To my knowledge there are only a small number of previous images of this subject. Of those, the earliest is when it was identified in a 1974 Hα sky survey by astrophysicist Jean-Pierre Sivan ( ). it also appears in the ongoing Hα MDW Sky Survey ( The other more targeted images, though groundbreaking in their own ways, are either broadband RGB or RGB + Hα; and as such they can show only a vague reddish haze.

Sivan 2 is indeed a very faint target. This image integrates 12 hours each of Hα, SII, and OIII data (all filters 3nm). I also captured a few hours or broadband RGB to produce properly calibrated stars.

This is an HSO image in which (Hα) is mapped to the red channel; SII is green, and OIII is blue. The areas with both abundant red Hα and green SII combine to create strong golden tones of course; but with the stronger Hα in the red position there are descent reds as well where only Hα exists, unlike in SHO (Hubble palette) images.

Aside from the aesthetics, this tricolor NB image reveals details about Sivan 2’s gaseous structure entirely missed in earlier photographs. The surprising relative abundance of OIII might indicate a specific evolution of this area, perhaps as an ancient planetary nebula; but I will leave that to the astrophysicists.



Jeffrey K Lovelace
License: None (All rights reserved)

Sky plot

Sky plot


Sivan 2 (Siv 2, Siv2), 


            Jeffrey K Lovelace