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.

Jelly Fish Nebula

 About

Here are all Capture Details for this extensive project!

The Jellyfish Nebula is a well known object among amateur astronomers. It is especially noted for it's obvious photographic nature containing a lot of blue and red. It is also rich in hydrogen alpha (Ha) and sulfur iii (Sii) and needs more capture time for Oxygen iii (Oiii.)

IC443 lies on the foot of one of the twins of the constellation Gemini, Castor between the bright stars Tejat and Propus.

Image courtesy of Stellarium

Both Ha and Sii have wavelengths in the Red spectrum while Oiii is aligned to the Blue spectrum.  

Some Light Science

The Jellyfish Nebula, or (Index Catalogue) IC 443, is the remnant of a supernova lying a relatively close distance in astronomical terms of 5,000 light years from Earth. IC 443 may be the remains of a supernova that occurred 3,000 - 30,000 years ago. IC 443 is one of the best-studied cases of supernova remnants interacting with surrounding molecular clouds. IC 444 is a nebulous region near Tejat or μ Gem

SHO

Commonly known as the Hubble Palette where Siii is mapped the the Red channel; Ha to the Green channel; Oiii to the Blue channel.

SHO w/ RGB Stars

HOO

Ha to Red; Oiii to both Green and Blue

Ha

68 exposures @ 180" (3h 24') 

Oiii

78 exposures @ 300" (6h 30') 

Sii

30 exposures @ 300" (2h 30')