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Heart Nebula, SHO

The Heart Nebula in SHO. 3 hours and 29 minutes of Hydrogen-α, Oxygen III and Sulfur II using 5nm and 3nm Astrodon filters and a monochromatic CMOS camera sensor.

Processing Details


Star allignment of the linear H, OIII and SII data with StarAllignment, Hydrogen-α frame as a reference.

Frames were cropped with DynamicCrop using the same process.

The background noise of the frames was reduced with Automatic Background Extraction.

The Pixel Math formula:

  • R: SII * .6 + Ha * .4

  • G: Ha * .6 + OIII * .1

  • B: OIII * 1

Auto-stretch of the SHO integration with the Screen Transfer Function (STF) and Curves Transformations.

Blue reduction 0.40 with SCNR.

Noise Reduction with ACDNR.

Histogram Transformation optimisations.


Selective Sharpening with High Pass Filter.

Tech Card

Date / Location

Middle of Februrary 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

70 x 120" Ha subs (Gain 200, Offset 50/16, Binning 2x2)

73 x 120" OIII subs (Gain 200, Offset 50, Binning 2x2)

66 x 120" SII subs (Gain 200, Offset 50, Binning 2x2)

Total Integration Time

3hrs 29mins

Calibration Frames

25 Darks, 20/20/30 Flats for Ha/OIII/SII


PixInsight 1.8 Core