Jelly Fish Nebula Capture and Processing

All Images

Equipment

Mount: iOptron GEM 28

Optical Train Equipment: 

• William Optics Zenithstar 61II APO Doublet Refractor
• William Optics Adjustable Flat61 for Z61
• ZWO Electronic Focuser
• ZWO 7-Position Electronic Filter Wheel for 36mm Unmounted Filters (Version II) 
• Antlia 3.0nm Narrowband Sulfur II (SII) Pro Imaging Filter - 36mm Unmounted
• Antlia 3.0nm Narrowband Oxygen III (OIII) Pro Imaging Filter - 36mm Unmounted
• ZWO 7.0nm Narrowband Hydrogen Alpha (Ha) - Filter - 36mm Unmounted
• R (Baader Planetarium LRGB 36 mm Round CCD Filter )
• G (Baader Planetarium LRGB 36 mm Round CCD Filter )
• B (Baader Planetarium LRGB 36 mm Round CCD Filter )
• Dew Straps for Guide Scope and Refractor.

Guiding: 

• William Optics 32mm f/3.75 UniGuide Guidescope
• ZWO 120mm mini (red filter)
• ASI Air Plus
• Used previous calibration
• Dither: Small, every 2 frames

  Acquisition: 

• ASI Air Plus using Plan Mode
• Flats & Flat-Darks using Spike-a-flat and NINA Flat Wizard (Dynamic brightness)
• Darks using ASI Air Plus
• (No Bias frames)

Capture Data Calibration Frames

My Google Spreadsheet

Processing

Preprocessing

1. Used Blink to eliminate obvious errors, clouds/elongated stars.
2. Used Subframe Selector to eliminate subs:
   - Full Width Half Maximum
   - PSF Signal Weight
   - Eccentricity
3. Weighted Batch Preprocessing Script
   - Cosmetic Correction
   - Subframe Weighting (defaults)
   - Image Registration
   - NO Image Integration
   - Output Pedestal (DN) = 100
   - Grouping Keyword of FILTER
4. Opened registered files in Blink to find the frame with the least amount of gradient.
5. Normalized Scale Gradient script using previous step to define the reference frame
   - All defaults except checking 'Auto Exit'
6. Used NSG's Image Integration to create stacked image with no changes.

Linear Processing

1. Dynamic Crop
2. Dynamic Background Extraction
3. Linear Fit was applied to G & B using R as base.
4. Channels were combined with ChannelCombination
5. Photometric Color Calibration 
6. Color Calibration
7. Background Neuralization
8. Linear Noise Reduction using MultiscaleLinearTransform
9. Another Linear Noise Reduction using MultiscaleLinearTransform

Non-Linear Processing

1. Used EZ Soft Stretch Script to bring to linear state using defaults.
2. Used EZ Star Reduction to make stars smaller.
3. Extracted the luminance from the combined RGB to create a synthetic luminance.
4. Removed the stars using Starnet++
5. Created a Range Mask to protect the nebulosity.
6. Used HDRMultiscaleTransform to brighten and sharpen image slightly.
7. Used LocalHistogramEqualization to step up the contrast. (25)
8. Used LocalHistogramEqualization again to step up the contrast. (75)
9. Used Curves to boost the overall nebula brightness and the blue channel.
10. Did NOT use SCNR to remove Green as I liked the way it looked.
11. Used MultiscaleLinearTransform to sharpen the nebula. It really improved the head of the Jellyfish.
12. Added the stars back into the RGB image using Pixel Math.
13. Blurred the RGB image with Convolution.
14. Used LRGBCombination with the synthetic luminance file to sharpen the image.
15. Used LRGBCombination/Chrominance Noise Reduction  with the synthetic luminance file to enhance the color and smooth the noisy background.
16. Used ICCProfileTransformation to ready image for the web.