Horsehead nebula revisited

Since we are coming to the end of winter, I thought that I had better make full use of the opportunity to image the Horsehead nebula. Otherwise I may have to wait another 8-10 months before I can image it again. I was particularly keen to try imaging it with the Astronomik Deep Sky RGB filters and CLS-CCD filter. But I also did a few H-alpha images to see what it could add.

Equipment used:

ZWO ASI178MM-cooled camera, Samyang 135mm F2.0 lens, Geoptik EOS to T2 adapter, iOptron ZEQ25, Lacerta MGEN autoguider, TS 8×50 finder scope used as guide scope, Microsoft Surface Pro 3 with Nebulosity 4 for image capture.

Images were pre-processed with Nebulosity, aligned and stacked in Deep Sky Stacker. These L(CLS-CCD) RGB & H-alpha images were then stacked together to form the colourimages in Nebulosity. Post-processing was then done in StarTools and final image adjustments done in Capture One Pro 8.

Settings used: Gain 300, 1 min for CLS-CCD (about 50 subs) and RGB subs (about 40 red, 20 green and 12 blue). Gain 300 7 x 2 min subs for H-alpha.

First is the LRGB stack with the Astronomik CLS-CCD and Deep Sky RGB filters. I am pretty impressed with this set of filters, although I have not compared it to the older Type 2c Astronomik LRGB filters; I basically skipped this and went narrowband imaging in the beginning due to the presence of moonglow.

Horsehead nebula in LRGB, with CLS-CCD for luminance channel, and Astronomik Deep Sky filters for RGB
Horsehead nebula in LRGB, with CLS-CCD for luminance channel, and Astronomik Deep Sky filters for RGB

I did manage to capture a few subs with the Astronomik 12nm H-alpha filter, so I decided to see what it would look like stacked together. Even with just 14 mins of integration time, there is considerable detail to be seen. But that is 14 mins at F2.0, which is the equivalent of nearly 2 hrs at aperture of F5.6.

Stack of H-alpha 7 x 2min subs @ Gain 300
Stack of H-alpha 7 x 2min subs @ Gain 300

Now I thought to myself, what would the image look like if I substituted the red channel with the H-alpha image. As you can see, it brings up much more detail and contrast to the dust clouds around the Horsehead. I did have to boost the red channel for this stack, as the amount of red channel captured was much less than the green and blue, owing to the capture of only 12nm in the H-alpha region.

H-alpha image used for the red channel instead
H-alpha image used for the red channel instead

But it just goes to show what the great camera the ASI178MM-cooled is, and how well it works with the Samyang 135mm F2.0 lens.

Boon