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J K Lovelace

Location of Photo:

Sierra Remote Observatories

Date/Time of photo:

2019-10-01 until 2019-11-25


FLI ML-16070M and Takahashi FSQ-106EDX4


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 (http://articles.adsabs.harvard.edu/full/1974A&AS...16..163S ). it also appears in the ongoing Hα MDW Sky Survey (https://www.mdwskysurvey.org/). 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.