IC434 - The Horsehead Nebula
From Wikipedia:
The Horsehead Nebula (also known as Barnard 33 or B33) is a small dark nebula in the constellation 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.
The nebula was discovered by Scottish astronomer Williamina Fleming in 1888 on a photographic plate taken at the Harvard College Observatory.
My words:
Well, where to start.
After weeks of bad weather (OK, the days were bright and clear but the nights were cloudy) I finally got a chance to take the rig outside and try my hand at imaging.
I previously spent a night tuning the guide camera settings to remove the noise and hot pixels. I saved the setting religiously, in the expectation that Ekos would be working perfectly when the next chance to image arose. Nope. Not to be - the old, broken, non-functional settings had returned and overwritten my evening’s work. I said lots of rude words at that point and put all the working values back. (I’ve since found where I think the incorrect values are coming from and manually edited them. We’ll see if that worked or not.)
I had originally planned to image an object that isn’t listed in Stellarium. Going by the shape of it, it’s a supernova remnant, and would make a great image. Except that it didn’t rise above the roof of my house until late in the night. The Pleiades were next on the list of desired targets, but they’re hidden by the fence behind me, so no luck there.
Then I remembered that I hadn’t managed to capture the Horsehead Nebula in any great detail. (There is an image of it somewhere here, but it’s very small and dim.) So with what time I had left, I grabbed as much data as I could.
I’ve noticed that the amount of light pollution in my suburb has increased over the past year, and this data set is no different. Washed out colours, poor contrast between the nebulae and the background. It’s really depressing if I start to think about it. (Anyone got a spare block of land with dark skies where I can live?)
The images were all stacked in SiriL, as usual. This time around I processed the resultant output twice after using starnet++ to split out the stars and nebula into two images. The first I tweaked the resultant files with SiriL before recombining them into one image. The second one I used Affinity Photo to process the two images and then combine them.
To my eyes, the Affinity image looks better because there aren’t large purple ‘shadows’ in the halo around Alnitak.
Where to from here? More data, as always! Although I’ll be using the L-Enhance filter to capture more of the Hydrogen-Alpha goodness, and (hopefully) cut down on the glare from Alnitak and the other bright stars in the area. I just need another clear night. I might even put the diffraction filter on the front of the scope and get some cool diffraction spikes on the stars, too.
Update - 2024-01-01
New Year’s Eve? I don’t need to party on NYE when I have an entire sky of stars and sights to see.
So I had the rig out and - miracle of miracles - the guiding worked perfectly all night long! No losing the guide star, no crashing after a dither operation. Just a smooth run with an average error of 1 arc-second or less for the entire session. It also appears that Ekos is remembering my settings - although I have them memorised so can easily put them back in - if I remember!
The auto-focus routine, on the other hand… It didn’t want to play well for some reason. Luckily, I knew how many steps to move the EAF and get a focus that was close enough. Given that 8800 EAF steps moves the focus tube about 15mm, I feel that the difference between positions 8800 and 8850 will be too small for me to see.
So then it was a matter of kicking off a sequence of 2-minute exposures and retiring inside to faff around on the computer.
With the L-Enhance filter in place, the halo around Alnitak (the bright star to the left) is very much reduced. The difference in the halo around it is noticeable when comparing the images below. Although I did forget to add the diffraction-spike generating filter…
Image 1 data:
- Gain: 100
- Offset: 10
- Temperature: 0 degrees C
- Exposure: 60 seconds
- Frames: 61 Lights, 50 Darks, 25 each of Flats and DarkFlats (61 minutes integration in total)
- Filter: UV-IR Cut
- Processed with SiriL (stacking, pre-processing and star removal with Starnet++) then finished in Affinity Photo v2 and also in Siril
Image 2 data:
- Gain: 100
- Offset: 10
- Temperature: 0 degrees C
- Exposure: 120 seconds
- Frames: 61 Lights, 50 Darks, 25 each of Flats and DarkFlats (122 minutes integration in total)
- Filter: Optolong L-Enhance
- Processed with SiriL (stacking, pre-processing and star removal with Starnet++) then finished in Affinity Photo v2
Equipment: SW72ED @ 420mm / HEQ5-Pro / ASI183MC-Pro / SV165+SV305 / Kstars/Ekos
This image uses only the data from the NYE session - the L-Enhance filter really highlights the H-Alpha signal, hence the overall orange tint.
The final image combines both data sets into one image. THe H-Alpha data really boosts the nebula behind the horse head, and adds some subtle detail to the ‘Flame’ nebula at the left.