Celestial hemisphere:  Northern  ·  Constellation: Cepheus (Cep)  ·  Contains:  Iris Nebula  ·  LBN 475  ·  LBN 483  ·  LBN 487  ·  LBN 495  ·  LDN 1168  ·  LDN 1170  ·  LDN 1171  ·  LDN 1172  ·  LDN 1173  ·  LDN 1174  ·  NGC 7023  ·  PGC 166711  ·  PGC 2817439  ·  Sh2-136  ·  T Cep  ·  VdB139  ·  VdB141
Iris Nebula (May 2022), Paul Macklin
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Iris Nebula (May 2022)

Revision title: Process refinement

Iris Nebula (May 2022), Paul Macklin
Powered byPixInsight

Iris Nebula (May 2022)

Revision title: Process refinement

Equipment

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Acquisition details

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Description

Current processing steps (revision D): 
Steps in AstroPixelProcessor: The main goal here (besides stacking) is to get a good preliminary stretch, good star colors with somewhat reduced intensity, and minimize light pollution.
+ Stack as normal.
+ Remove light pollution at 30% stretch
+ Stay at 20% bg, 3 sigma, 2.5% base
+ Calibrate star colors as normal
+ Reduce stars with intensity at 85%, size at 90%.
+ Use the built-in sharpening at around 3% to bring out more details for the inner core. Optionally, increasing the HL value may show the central star a little better. 
+ Export as tif

Steps in photoshop (round 1): The main goal here is to clean up the colors and contrast, and light curves.
+ Crop and rotate as needed to 6000 x 4000
+ Auto color (with caution--watch for washed out bright details)
+ Adjust levels. Auto is probably okay. It'll typically increase black level to around 20 and choose a gamma of 1.49
+ Adjust curves. Since auto levels already applied a brightening, I typically might use linear contrast here.
+ Adjust hue/saturation in the blue, cyan, and magenta channels by increasing saturation +50 and decreasing brightness -25. This helps bring out colorful details in the center.
+ Optionally reduce yellow saturation -15 to -25 to deal with Tau-Cep

Steps in Topaz: Here we want to reduce noise with a minimalist touch to avoid artifacts.
+ Choose low light.
+ Set Reduce noise to 1%
+ Set Enhance sharpness to 5%
+ Set Recover original detail to 50% to help reduce any sharpening artifacts.
+ All other settings at 0.

Steps in photoshop (round 2):
+ Adjust levels one last time. Keep gamma at 1. Whatever auto suggests as a black clipping, probably cut it in half.
+ Adjust curves once more as needed. Probably linear contrast.
+ Save and export as desired.

Comments

Revisions

  • Iris Nebula (May 2022), Paul Macklin
    Original
  • Iris Nebula (May 2022), Paul Macklin
    B
  • Iris Nebula (May 2022), Paul Macklin
    C
  • Final
    Iris Nebula (May 2022), Paul Macklin
    D

B

Title: Increased to 9 hours of data

Uploaded: ...

C

Title: Increased to 11.75 hours, improved processing.

Description: I revised my processing steps a bit in this step, with more refined stretching in AstroPixelProcessor in particular, and better blending in Topaz. More details in the main description.

Uploaded: ...

D

Title: Process refinement

Description: I used some of the built-in sharpening in AstroPixelProcessor to bring out more fine detail in the inner iris.

Uploaded: ...

Sky plot

Sky plot

Histogram

Iris Nebula (May 2022), Paul Macklin