Un ritratto di varie nebulose di emissione nel Gemelli meridionale e nell'Orione settentrionale. In cima si trova il brillante gruppo di stelle Messier 35, con il piccolo più d
3579 x 5400 px | 30,3 x 45,7 cm | 11,9 x 18 inches | 300dpi
Data acquisizione:
17 marzo 2021
Altre informazioni:
A portrait of various emission nebulas in southern Gemini and into northern Orion. At top is the bright star cluster Messier 35, with the small more distant open star cluster NGC 2158 below and to the right of it. Left of centre is the shell-like supernova remnant, IC 443, aka the Jellyfish Nebula. The small blue reflection nebula above and to the left of it is IC 444 amid a field of fainter emission nebulosity. The round and bright nebula at bottom is IC 2174 in Orion, aka the Monkeyhead Nebula. It is mostly an emission nebula but has some blue reflection components. The smaller round red nebula above it is Sharpless 2-247. It appears to be an ionized HII region, as a form of bubble, but is not a planetary nebula. So this is a field of various forms of nebulas: emission, reflection and supernova remnants. Missing is an obvious planetary nebula or dark nebula. The orange star to the right of the Jellyfish is Propus, or eta Geminorum. This is a stack and blend of filtered and unfiltered exposures, the latter set maintaining the natural star colours, and avoiding the haloes introduced by the filters, particularly the L-eXtreme. The image is a blend of: 10 x 6 minutes at ISO 800 without a filter + 8 x 12 minutes at ISO 1600 with an Optolong L-eNhance dual narrow-band filter + 6 x 16 minutes at ISO 3200 with the Optolong L-eXtreme vary narrowband filter, the latter set taken at the end of the sequence when the field was quite low. Through masking the L-eXtreme images contributed only some of the nebulosity, particularly the subtle cyan fringes on the leading edges of IC 443 — it is the Oxygen III cyans that the L-eXtreme is good at picking up. All were with the Canon EOS Ra camera and through the SharpStar 76mm triplet apo refractor with the EDPH reducer/flattener for f/4.5. Guiding was with the multi-star Lacerta MGEN3 stand-alone auto-guider, which also controlled the camera shutter and performed dithering between each frame to shift each exposure by a few p
