Scroll Down

California Nebula, HaRGB

1,000 light years away, the rich of hydrogen nebula NGC 1499 burns like an eternal flame in the constellation of Perseus, an Ancient Greek demigod, founder of Mycenae.

Processing Details

Star Alignment of the linear Ha, Red, Green and Blue data using PixInsight's Star Allignment (Hydrogen-α frame as a reference).

Dynamic Crop on all frames using the same process.

Background Noise Resduction with Dynamic Background Extraction (using 50 points on non-nebula areas).

Linear Fit was performed on all the frames using the Red frame (STF was applied on it, ScreenTransferFunction with linked RGB channels).

Noise Reduction was performed with MultiscaleLinearTransform, 4 layers with the following settings (R as default):

  • Layer 1: Threshold 0.500, Amount 0.50, Iterations: 1

  • Layer 2: Threshold 0.500, Amount 0.50, Iterations: 1

  • Layer 3: Threshold 0.500, Amount 0.50, Iterations: 1

  • Layer 4: Threshold 0.500, Amount 0.50, Iterations: 1

The RGB frame was created using the Channel Combination process, where the frames were mapped accordingly. The red was reduced with SCNR at 0.25.

Further noise reduction was applied with ACDNR and StdDev of 1.0 and Amount 0.50.

Star Reduction was applied with Star Mask and Morphological Transformation, both set at default settings.

Curves Transformations were applied to boost RGB/K and Saturation.

Final touches were performed with Photoshop that include a Selective Sharpening with High Pass Filter (with radius 1.5).

Tech Card

Date / Location

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

Equipment

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

Sensor Cooling Temperature: -15C

Filters: 1.25 5nm Astrodon Ha, 1.25 Astrodon LRGB Gen2 E-Series Tru-Balance Red, 1.25 Astrodon LRGB Gen2 E-Series Tru-Balance Green, 1.25 Astrodon LRGB Gen2 E-Series Tru-Balance Blue

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

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

13 x 180 Red subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

9 x 180 Green subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

9 x 180 Blue subs (Unity Gain, Gain: 139, Offset: 21, Binning 1x1)

Total Integration Time

2hrs 48mins

Calibration Frames

20 Darks, 20 Flats (Ha flat for Ha, and Luminance flat for RGB

Software

PixInsight 1.8 Core

Photoshop

SharpCap