Rosette Nebula, SHO, 2019

5,000 light years away from our planet, an open cluster of young and bright suns excite nearby atoms to produce this flowery nebula, the Rosette Nebula.

Capturing the Light

I collected about 5 hours of Hydrogen-α (Ha), Oxygen (OIII) and Sulfur (SII) using my light-pollution fighting setup from my light polluted garden, using dedicated scientific narrowband filters and an astro-monochromatic CMOS sensor constantly cooled at -15C.

Processing Details


I calibrated the frames, stacked them and star-aligned them using Star Alignment. Then, I used Pixel Math algorithms to process the data with a specific pattern that NASA is using to produce the stunning photos from the data they gather from the space Hubble telescope, Hubble palette, SHO (stands for Sulfur II, Hydrogen-α and Oxygen III).

I spent 3 hours fine-tuning the algorithm, performing a series of pixel-level arithmetic and logical operations between images and suddenly I got the perfect result. Then, I applied noise reduction with ACDNR that stands for Adaptive Contrast-Driven Noise Reduction, a highly flexible implementation of a novel noise reduction algorithm. I also used Automatic Background Extractor, Histogram Transformation, auto-stretched it with STF (Screen Transfer Function) and improved the contrast and saturation with Curves Transformations.


In the end, I applied some final touches with Photoshop including a Selective Sharpen method with the High Pass Filters, which worked really well.

Tech Card

Date / Location

26th & 27th February, 25th, 28th March 2019, Bedworth, GMT+0, United Kingdom, Bortle Class 5 ~SGM: 19.57 mag./arc sec2


Camera: ZWO ASI 1600MM-PRO USB 3.0 Mono (Type CMOS)

Sensor Cooling Temperature: -15C

Filters: 1.25" 5nm Astrodon Ha, 1.25" 3nm Astrodon OIII, 1.25" 3nm Astrodon SII

Imaging Telescope: Takahashi FS-60CB

Correcting Lens: Takahashi Reducer 0.72x (composite focal length at 264mm and focal ratio at f/4.9)

Mount: iOptron CEM25EC

Image Quality

12Bit ADC (FITS)

Exposure time per image / number of composities and sensitivity

50 x 180" Ha subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

42 x 180" OIII subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

42 x 180" SII subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

Total Integration Time

6hrs 42mins

Calibration Frames

20 Darks, 20 Flats


PixInsight 1.8 Core