Imaging Diary - IC1396 Elephant's Trunk Nebula

Essential Information

• Name - IC 1396 Elephant's Trunk Nebula
• Constellation - Cepheus
• RA - 21h39m00s
• DEC - +57°29′24″
• Apparent Magnitude - 3.5
• Apparent Size - 1.5°
• Actual Size - >100ly whole nebula, 20ly for the 'Trunk'
• Distance - 2400ly from Earth

Successes and Failures

Admittedly this was a long shot of a target with an astro-modified DSLR, it is a much better narrowband target which can help bring out a wealth of details and looks great in the famous Hubble Palette . Add to that the fact that it is currently at its lowest point in the sky until the late summer months and you have a lot of atmosphere in the way and a nice light pollution gradient from the glow of London in the North.

Nevertheless I was eager to try a nebula target out with the newly astro-modified DSLR and the now stable mount and guiding I've worked so hard towards for months.

The result was not surprising but equally exciting as I had never managed to tease any H-alpha out of images with the DSLR before. The image is over-processed, noisy and pretty ugly overall but all the same it was worth the challenge and did prompt me to look into combatting the light pollution in future as well as push me towards considering a narrowband capable imaging camera in the future.

Acquisition Details

• Date - 2020-03-23
• Imaging Scope - Skywatcher 130PDS @ 650mm
• Imaging Camera - Canon 400D Astro-Modified for Ha response
• Guide Scope - Svbony 50mm Guide Scope
• Guide Camera - ZWO ASI290MM Mini
• Light Frames - 48x300s for 4 hours total
• Dark Frames - 10x300s
• Flat Frames - 60x0.5s with DIY Flat Planel
• Flat-Dark Frames - 50x0.5s
• Bias Frames - 50x0.00025s (1/4000 minimum exposure on camera)
• Moon Age - 28.73 days
• Moon Phase - 0.72%
• Bortle Sky - Class 5 Suburban Skies
• Pixel Scale - 1.8 arcseconds per pixel
• Field Radius - 1.024 degrees
• Platsolving - Astrometry.net Solution
• Astrobin - Astrobin Link

Processing Details

• Stacking - Astro Pixel Processor

  • Calibrated Light frames with Bias/Flat/Dark/Dark Flat
  • Registered and performed Local Normalisation without Background Neutralisation
  • Integrated best 85% of frames for 48 total
  • Drizzled with Bayer Drizzle at Scale 2.0 and TopHat Kernel at 1.0 droplet size
  • Saved final stacked image in linear 16bit FITS format

• Processing - StarTools

  • Bin - Image 50% back to original size
  • AutoStretch - Reveal image and problems
  • Crop - Removed edges of stack and worst coma
  • Wipe - Remove light pollution gradients
  • AutoDev - Re-do Stretch with Trunk as Region of Interest (ROI)
  • Contrast - Push background down and bring signal forwards
  • HDR - Reveal large scale structures
  • Sharp - On 'Large' to reveal medium-Large scale structure detail
  • Decon - Reverse atmospheric seeing effects and reveal medium-scale detail
  • Life - 'Less=More' preset to reduce background, enhance nebulosity
  • Color - Bring colours as close to natural as possible
  • Tracking Off - Grain Equalisation noise reduction at large scale to remove worst noise
  • Flux - Introduce small amount of sharpening back into the image on areas exclusding stars
  • Shrink - Reduce star sizes by 1 pixel

• Final Touches - Photoshop CC 2020

  • Duplicate - Original image to save original state in bottom layer
  • HLVG - Hasta La Vista Green to remove residual green cast from the image
  • Duplicate - Copy the HLVG applied image for fallback purposes
  • Camera RAW Filter - Apply balancing to White, Black, Shadows, Highlights, Saturation to balance overall image
  • Camera RAW Filter cont. - Apply small amount of sharpening, smooth noise with Luminosity Noise Reduction, Colour Noise Reduction
  • Curves Adjustment Layer - Apply curves layer on top of the image to introduce a subtle s-curve to bring up highs, bring down lows for overall final contrast tweaks