LBN902 is a small HII region that seems to have been missed by Sharpless, unless he figured it was already included in Sh2-273 (the Cone/Christmas Tree area). It appears to be a distinct object, brighter and with its own small features, separated from the more diffuse nebulosity of the huge Sh2-273 area by a deep lane of dust.
I asked Charles Pevsner to gather some narrowband data for me from the scope we share at DeepSkyChile, which I’ve processed here using an HOO palette, as the SII was faint and indistinct. LBN902 is the bright feature at center. The triangular dark nebula at left is Barnard 39, though it’s not clear how much of that area he meant to catalog as B39 as he doesn’t provide a size, nor was it on any of the pictures in his atlas. (Two of the dark patches are noted as LDN1609 and LDN1610, but the others were missed by Lynds.) The small open cluster at center-top is NGC2259.
What I am most curious about is the strong OIII signal at right. Looking at widefield images I’ve taken in the past, this OIII signal extends over 1 degree, and it doesn’t follow the usual pattern of HII regions, where the OIII is faint and in the center of a denser area of H-alpha signal–in fact Sh2-273 already has a patch of OIII signal that follows that pattern exactly. This is a separate area of unusually strong ionized oxygen where there is little hydrogen.
If anyone knows more about the astrophysics of this particular area, please let me know. I’ve searched the literature to little avail. Regardless of where it came from, it provides for striking color contrast in this image!
- Exposures (-10ºC, gain=0):
- Ha: 40×300s
- OIII: 35×300s
- Total exposure time: 6.25 hours
- Taken remotely from DeepSkyChile, Jan 25 and Feb 2, 2024 – data acquired by Charles Pevsner
- Telescope: Takahashi TOA-130 with flattener (f/7.7)
- Camera: ZWO ASI6200MM-Pro
- Mount: 10Micron GM1000HPS
- Guiding: none
- Acquisition: NINA
- Processing: AstroPixelProcessor, PixInsight
Deep-sky Imaging 