The Horsehead and Flame Nebula
The Horsehead Nebula (also known as Barnard 33) is a small dark nebula located about 1,375 light-years from Earth in the constellation of Orion. The nebula is located just to the south of Alnitak, the easternmost star of Orion's Belt, and is part of the much larger Orion molecular cloud complex. It appears within the southern region of the dense dust cloud known as Lynds 1630, along the edge of the much larger, active star-forming H II region called IC 434, a bright emission nebula that forms a curtain behind the Horsehead, giving it its distinct silhouette. The Flame Nebula (NGC 2024) is an active star forming region with a dense cluster of newly born stars, backlighting the dust and gas, and giving it the distinct flame appearance.
February 28, 2025
This is a 2-panel mosaic of the Horsehead and Flame Nebula. Data was captured over 4 nights. I ended up with 10 hours on the Horsehead panel and 8 hours on the Flame panel, as I had to toss about 2 hours on the flame due to high clouds. I decided that should be enough integration time, and brought the data in and got it all stacked.
I’ve put off processing this for some time, since I knew that dealing with the filter halo around Alnitak was going to be a significant challenge. I attempted it a couple times, but was not happy with the result each time. I feel better about how it turned out, but it took several hours of meticulous masking with SetiAstro FAME tool, and careful, iterative processing to get it to a point where I felt it was presentable. I’m ready for my next target!
Technical Details
Imaging Telescope: Astro-Tech AT115EDT
Imaging Camera: ZWO ASI533MC Pro
Mount: Sky-Watcher EQ6-R Pro
Filter: Antlia ALP-T Dual-Band 5nm 2"
Accessories: Antlia OAG and Filter Drawer Assembly, Astro-Tech AT115EDT .8X Reducer, ZWO ASIAIR Plus, ZWO EAF
Software: StarNet, PixInsight, BlurXTerminator, NoiseXTerminator, SetiAstro Star Stretch, SetiAstro Statistical Stretch, Siril, ZWO ASIAIR
Guiding Camera: ZWO ASI174MM
Imaging Dates: January 27, 29, 31, and February 5, 2026
Frames (gain 101.0) f/4.9 -10c: 360x180” (18h)
Integration Time: 18h
Darks/Flats/Dark Flats: 30/30/30
Bortle Dark-Sky Scale: 6.00