The Horsehead Nebula is one of those targets I've admired in other people's images for years, so it was about time I had a go at it myself. It sits in the constellation Orion alongside its neighbour the Flame Nebula, and this is the kit I pointed at it on the night:
- William Optics Zenithstar 81 + Sky-Watcher HEQ5 Pro
- ZWO ASI 294MC Pro + Optolong L-eXtreme filter
- William Optics 50mm Slide-base Uniguide Scope + ZWO ASI 120MM Mini
- ZWO ASIAir Pro
The Horsehead itself is a dark nebula, a dense pillar of dust that creates a silhouette against the glowing hydrogen emission of IC 434 behind it, shaped exactly like a horse's head seen in side profile. The red you see in images comes from that glowing hydrogen background, not the Horsehead itself. Once you've seen it, you can't unsee it.
My plan was to frame the shot so that the Flame Nebula, which sits adjacent to the Horsehead, would fit in a single image. That should be possible with my telescope, which has a focal length of about 450mm with the reducer fitted. For exposures I went with three minute subs, which I reckoned would be enough to gather a decent amount of signal without blowing out the image too much, since there are some very bright stars in that part of the sky.
Time was the other constraint. As with my previous session on the Orion Nebula, the constellation drops behind my neighbour's house around midnight, so I had to make the most of it while I could. With some preparation and planning ahead, I thought about five hours of data was achievable. To squeeze out every minute, I set the telescope up while it was still light, then did a polar alignment as soon as it started getting dark, ready to begin shooting the moment proper astronomical darkness arrived.
How the night went
For once, the setup routine behaved itself. I balanced the rig, got everything connected and ran a quick polar alignment, all of which went smoothly. I slewed the telescope across to the target and it was soon capturing three minute sub exposures, on track for roughly the five hours I was hoping for.
The only concern was the weather, which had changed during the course of the day. Some cloud was due to roll in, though it looked intermittent and high, so I hoped it would only wash a few frames out a little rather than ruin the night. Worst case, I'd filter out the bad subs when pulling everything into PixInsight and keep only the best quality frames, hopefully still ending up with a respectable image.
This was my first time shooting this target, so I genuinely didn't know how the final image would turn out. If nothing else, it serves as a baseline for future attempts. That's astrophotography all over really: it's a bit of a minefield, you never quite know whether you'll run into back focus issues, weather, guiding problems or something else entirely, and you keep learning every time you put the telescope outside.
So did the night pay off? Here's the finished Horsehead and Flame image:
Horsehead NebulaWilliam Optics Zenithstar 81 APO · ZWO ASI 294MC ProView in gallery →
The whole session is in the video above, and if you'd like to join me for the next target, a subscription on YouTube is the best way to do it. Clear skies!