Target: Horsehead Nebula
Date: January 15, 2026 - January 18, 2026
Location: My Backyard in Georgetown, Texas
Sky Conditions: Clear skies, 23-44°F, Wind: 10-15 mph, Moon: 8% illuminated.
Bortle Class: 5

This week’s image resulted from a minor error that prompted me to experiment with a new processing technique. We had four consecutive clear nights, and I wanted to make the most of the nearly moonless sky to capture the Horsehead Nebula. Typically, I photograph the Horsehead using a narrowband filter, but this time, I wanted to gather as much light as possible using only the IR filter to create a broadband image.

All 4 nights seemed to go smoothly as I photographed the nebula with the internal IR filter in my Seestar S50. However, I must have accidentally used the LP filter on the first night. When I opened the files on my computer, I noticed approximately 1000 x 20-second subframes using the LP filter. Since I didn’t want to discard a third of my subframes, I decided to combine the broadband RGB images with the narrowband images.

Once again, I consulted the processing guides provided by Philippe Bernhard and followed his instructions for processing OSC RGB and dual-band Ha OIII images.

https://astro-photographie.fr/wa_res/files/OSC5-Processing_of_OSC_RGB_and_dualband_Ha-OIII_images.png?t=

Unfortunately, before stacking the subframes, I encountered another issue. As my telescope tracked the Horsehead Nebula across the sky, it dipped behind our banana tree each night. I had to go through 3000 subframes to remove approximately 1000 frames that had banana leaves obscuring the sky. Despite this setback, the stack still contained about 11 hours of data, but I hate to waste any precious imaging time.

I’m certainly going to continue imaging the Horsehead through the end of February. It’s a beautiful object in the night sky and worth the time investment.

Post-Processing Workflow

Software Used: Siril, PixInsight, Photomator

Stacked broadband RGB and narrowband images in separate stacks in Siril using Naztronomy's smart telescope script
Cropped Images, applied AutoDBE, and exported .fit file for further processing in PixInsight
RGB Image:
BlurXTerminator: Correct Only
Plate Solved Image
Applied Spectrophotometric Color Calibration
BlurXTerminator: Default value
StarXTerminator: Unscreened / Removed Stars (RGB star Image will be used later)
NoiseXTerminator: Default on starless RGB image.
Statistical Stretch 2.0
Narrowband Image:
BlurXTerminator: Default value
StarXTerminator: Unscreened / Removed Stars (discarded narrowband star Image)
NoiseXTerminator: Default on starless narrowband image.
Extracted Ha and OIII channels with DBXtract.
Statistical Stretch 2.0 on Ha and OIII images.
Combined Image:
Combined non-linear Ha, OIII, and RGB images with Combined RGB and Narrowband script.
Curves Adjustments: Adjusted luminance, saturation, and RGB/K channels to add contrast and boost color.
RGB Star Image:
Seti Astro's Star Stretch. Color boost at .5 and SCNR checked.
Combined HORGB starless image with star image in pixel math using ~(~SL*~S).
Exported as PNG.
Photomator:
Adjusted white balance as final color correction.

21. Adjusted highlights level to reduce white clipping.