B33/NGC 2024 - The Horshead and Flame Nebula - Dec 2025 Image Processing Walkthrough.
December 17, 2025
My 2025 image of Barnard 33 nd NGC 2024
🔭 Project Summary
Target: B33 – The Horsehead Nebula (with NGC 2024 – The Flame Nebula)
Capture Dates: October 27 & 28, 2025
Constellation: Orion • Distance: ≈ 1,300–1,500 light-years
Type: Dark Nebula (B33) silhouetted against emission backdrop (IC 434) + Emission Nebula / H II Region (NGC 2024)
Imaging Period: October 27–28, 2025 • Total Integration: 5 h 59 m 30 s (LRGB + Ha)
Filters: L · R · G · B (ZWO 36mm Unmounted LRGB Gen II) + Ha (Astronomik 36mm 6 nm)
Telescope: William Optics FLT 132mm f/7 APO Refractor + P-FLAT7A 0.8× Reducer
Camera: ZWO ASI2600MM-Pro (−15 °C; Gain 0 LRGB, Gain 100 Ha)
Mount: iOptron CEM60 on custom steel pier
Processing: PixInsight & Photoshop
Location: Whispering Skies Observatory · Honeoye Falls, NY (USA)
Field Includes: IC 431, IC 432, IC 435, LBN 934, LBN 944, LBN 958, LBN 962
Table of Contents Show (Click on lines to navigate)
Special Note
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Abbreviations Used
BXT BlurXTermminator by RC-Astro
CC Cosmetic Correction
CT Curves Transformation Process
DBE Dynamic Background Extraction Process
ET Exponential Transformation
HDRMT HDR MultiScale Transform
HDRC HDR Composition
NXT NoiseXTerminator by RC-Astro
MLT Multiscale Linear Transform
PI PixInsight
PS Photoshop
SCNR Subtractive Chromatic Noise Reduction Process
SFS SubFrameSelector
SPCC SpectroPhotometric Color Calibration
STF Screen Transfer Function
STF->HT method – Drag the STF triangle to the base of HistogramTransformation, then apply it to the image to take it nonlinear.
SXT StarXTerminator by RC-Astro
WBPP Weighted Batch Preprocessing Script
Summary:
M42/43 HDR HaLRGB Processing Flow
Two-column swimlane summary aligned to your M42 2025 PixInsight → Photoshop sequence.
Processing this Image
(All Processing is done in PixInsight, with some final touches done in Photoshop)
1. Blink
I screened all subs and cal frames with Blink. I was surprised that I did not remove ANY frames collected for this image.
2. WBPP 2.8.9
All frames were loaded into WBPP:
Reset everything
Load all lights
Load all flats
Load all darks
Select - maximum quality
Reference Image - auto - the default
Select the output directory for the WBPP folder
Enable CC for all light frames
Pedestal value - auto
Darks - set exposure tolerance to 0
Lights - set exposure tolerance to 0
Lights - all set except for a linear defect
set for Autocrop
I chose NOT to use Drizzle processing.
WBPP run in 1:01:14 minutes - no errors
WBPP Calibration View
WBPP Post Calibration View
WBPP Pipeline View
3. Load Master Images and Create Color Images
Load all master images and rename them.
Master Ha -300-seconds
Mater LRGB-90-seconds
Using CombineChannels, create the Master RGB 30-second and the Master RGB 90-second color images
Master L, R, G, B 90-second images
Master_Ha image. (click to enlarge)
Master RGB 90-second image (click to enlarge)
4. Initial Process of Linear Lum data
Run DBE for the Lum linear image. Use subtraction for the correction method. Choose a sampling plan that avoids the nebulae and bright stars. (see below)
Run BXT - Correct only. This cleans up the stars at the corners. Not much to do in this image, as the scope is very crisp.
Run PFSImage script to measure star sizes. X = 2.67 Y= 2.43. This will influence the values used in BXT.
Run Full BXT - I am using an enhanced set of values to shrink stars more. These are about a third more than the measured star sizes. See the BXT Panel Snapshot below.
Run NXT V3; refer to the parameters in the snapshot below.
Run SXT - no need to save the Lum stars, as we will not be using them.
Master L Image DBE Sampling Plan (click to enlarge)
Master L- Before DBE (click to enlarge)
Master L after DBE (click to enlarge)
Background Subtracted by DBE (click to enlarge)
Measuring Star Sizes with PFSImage Script (click to enlarge)
BXT Settings Used. (click to enlarge)
NXT Panel used. (click to enlarge)
Master Lum Before BXT Correct Only, After BXT Correct Only, After BXT Full, After NXT
Final Master Lum Image
Master Lum Starless Image (click to enlarge)
5. Initial Process of Linear Ha data
Run DBE for the Lum linear image. Use subtraction for the correction method. Choose a sampling plan that avoids the nebulae and bright stars. (see below)
Run the PFSImage script to measure star sizes. X = 2.35, Y 2.17. This will influence the values used in BXT.
Run BXT Correct Only
Run Full BXT using the parameters in the screen snapshot below.
Run NXT V3; refer to the parameters in the snapshot below.
Run SXT - no need to save the Lum stars, as we will not be using them.
I want to combine the Ha and L data later on, so I ran a LinFit here, using the L as the reference.
Finally, I ran SXT to remove stars, but I did not preserve the stars - I will not be using the Ha stars going further.
Master Ha Sampling Plan (click to enlarge)
Master Ha Before DBE (click to enlarge)
Master Ha after DBE (click to enlarge)
Master Ha Background (click to enlarge)
PFSImage measuring star sizes on the Ha Master
BXT Params used
NXT Params used.
HA Before BXT, After BXT Fix Only, After BXT Full, After NXT V3
Master Ha before SXT (click to enlarge)
Master Ha Starless image (click to enlarge)
6. Process the RGB Masters
Run DBE using Subtractive correction
Select a background preview and run SPCC on the image
Run BXT - Correct only. This cleans up the stars at the corners. Not much to do in this image, as the scope is very crisp.
Run PFSImage script to measure star sizes. X = 2.57 Y= 2.2. This will influence the values used in BXT.
Run Full BXT - I am using an enhanced set of values to shrink stars more. These are about a third more than the measured star sizes. See the BXT Panel Snapshot below.
Run NXT - see params used in screenshot below
Run SXT and save Star images.
Master RGB 90sec Sampling Plan (click to enlarge)
Master RGB 90sec before DBE (click to enlarge)
Master RGB 90 sec after DBE (click to enlarge)
Master RGB Background removed (click to enlarge)
Master RGB 90-second before SPCC(click to enlarge)
SPCC Panel showing parameters used.
SPCC Regression results.
Master RGB after SPCC.
PFSImage panel showing star sizes.
BXT Panel showing parameters used.
NXT Params used.
Master RGB Master Before BXT, BXT Correct Only, Full BXT, After NXT Full
Master RGB before SXT.
Master RGB Starles Image
Master RGB Stars only image.
7. Go Nonlinear
Using the STF->HT Method, convert the linear Lum and Ha images to nonlinear. Remember that we did a LinearFit of the Ha to the L image, so use the STF when doing this.
Using the STF->HT Method, take the linear RGB image nonlinear.
Using Seti Astro Star Stretch, take the RGB Star image nonlinear. (See Panel snapshot below for parameters used).
Nonlinear Starting Lum Image (click to enlarge)
Nonlinear RGB image (click to enlarge)
The nonlinear RGB HDR image.
The Star Stretch Script and parameters used.
The resulting Star image
8. Process the Nonlinear Lum Starless Image
Use CT to lighten the outer tenuous nebulae and darken the core a bit
Apply HDRMT with 9 layers and “To Lightness” checked. This will open up blocked highlights. I tried various levels, but 7 seems best.
Apply CT
Apply LHE with a scale of 64, a contrast limit of 2.0, an amount of 0.1, and an 8-bit histogram. This is designed to enhance small-scale structures.
Apply LHE with a scale of 200, a contrast limit of 2.0, an amount of 0.1, and a 10-bit histogram. This is designed to enhance medium-scale structures.
Apply NXT V3 now (see parameters in the screenshot below).
Now do a final sharpening operation with MLT - see the screenshot below.
The initial L image (click to enlarge).
HDRMT applied (click to enlarge)
After LHE - Small Scale (click to enlarge)
NXT Params used (click to enlarge)
After CT (click to enlarge)
After CT (click to enlarge)
After LhE - Medium Scale (click to enlarge)
Apply NXT V3 (click to enlarge)
MLT Sharpening Panel
After MLT Sharpening run (click to enlarge)
9. Process the Nonlinear Ha Starless Image
Use CT to darken the outside and darken the core a bit.
Apply HDRMT with 7 layers and “To Lightness” checked. This will open up blocked highlights. I tried various levels, but 7 seems best.
Apply CT to adjust the tonescale after the previous step.
Apply LHE with a scale of 222, a contrast limit of 2.0, an amount of 0.10, and a 10-bit histogram. This is designed to enhance medium-scale structures.
Apply MLT Shaprening with params shown in the screensnap below.
Iniital Nonlinear Ha image(click to enlarge)
After HDRMT (click to enlarge)
After CT (click to enlarge)
After CT (click to enlarge)
After LHE Mid-scale (click to enlarge)
MLT Sharpen Parameters
After Sharpening.
10. Combine L and Ha image, and Process
Use PixelMath to blend the HA and L image. I tried different blend rates:
10% L - 90% Ha
25% L - 75% Ha
50% L - 50% Ha
I chose the second mix.
Adjust with CT
Create a GAME gradient mask that covers the Flame and the bright nebula near the Flame - call this the LHaMask
Apply HDRMT with the LHAMask. Use 7 layers and check “To Lightness”. This will open up blocked highlights.
Apply CT with the LHaMask
Use the RGBWOrkingSpace Panel to set the RGB coefficients to 1.0. We don’t want color scaling for future operations.
PM Blend example equation
10% L - 90 % Ha Blend (click to enlarge)
25% L - 75% Ha Blend (click to enlarge)
50% L - 50% Ha Blend (click to enlarge)
The Blended HaL image. (click to enlarge)
LHA Mask (click to enlarge)
CT Aplied with the LHA Mask in place (click to enlarge)
After CT (click to enlarge)
After HDRMT wIth the LHAMask (click to enlarge)
Set RGBWorkingSpace coeffcients to 1.0.
14. Process the RGB Image
Let's create some masks that we will be using with this image:
Use GAME to create the CoreMask. This gradient ellipse will be used to lighten the Trapezium area.
Use RangeSelection to create a RangeMask using:
Range of 0.5 to 0.8
Smoothness of 5
Create a Red ColorMask with the params in the snapshot below.
Use CT to boost it.
Create a Blue ColorMask using the parameters shown in the screenshot below.
Use CT to boost it.
Let’s start by dealing with those blown-out highlights. Apply HDRMT with levels = 8, “To Lightness’ and ‘Lightness mask’
Apply CT to adjust contrast and color saturation.
Apply the Inverted CoreMask and do a CT to darken the Trapezium area slightly
Now we want to inject the HaL image. The core area is already saturated, so we want to protect it before we apply this. So:
Apply the RangeMask
This will protect the core area
Use ChannelCombination in the ColorMode and enable only the Neutral channel, using the HaL Image.
Apply to the RGB HDR image.
The masked Area now seems too light. Let's invert the RangeMask and use CT to bring it in line.
Let’s try to bring out more detail in the RangeMask Area. Run HDRMT with the mask in place, and use Levels=10, ‘To Lightness.’
Now apply the Red Mask and use CT to adjust color, saturation, and tone.
Now apply the Blue Mask and use CT to adjust color, saturation, and tone.
Apply a final CT with no Mask.
Now I would like to ‘polish’ this starless image in Photoshop. Specifically, I want to use the Camera Raw Effects filters for Texture, Clarity and Dehaze filter, along with the colormixer.
Write the RGB HDR image to a 16-bit unsigned TIFF file
Pull into Photoshop and polish
Export to a new 16-bit unsigned TIFF file
Bring this back into PixInsight
The Core Mask (click to enlarge)
Params used to create the Red Mask
Params used to create the Blue Mask
The initial RGB HDR image (click to enlarge)
After CT (click to enlarge)
After Injecting the HaL image using the Inverted RangeMask (click to enlarge)
After HDRMT of the RangeMask area (click to enlarge)
After CT with the Blue Mask (click to enlarge)
The RangeMask
Initial Red Mask (click to enlarge)
After boosting with CT (click to enlarge)
Initial Blue Mask (click to enlarge)
BlueMask after CT boost (click to enlarge)
After HDRMT (click to enlarge)
CT with the Inverted Core Mask
After CT adjust with the RangeMask (click to enlarge)
After CT with the Red Mask (click to enlarge)
After A final CT with no Mask - Export this to Photoshop (click to enlarge)
Final Starless Image after Photoshop polish.
15. Add the Stars Back In
Using the ScreenStars Script, add stars back into our RGB starless image.
The script used to add the images back in,
Stars now added - Image ready for Photoshop Polishing!
16. Export the Image to Photoshop for Polishing
Save the image as a TIFF 16-bit unsigned and move to Photoshop
Make final global adjustments with Clarify, Curves, and the Color Mixer - slight tweaks really
Added Watermarks
Export Clear, Watermarked, and Web-sized JPEGs.
The Final Image!
The First Cropped Image
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Thanks,
Pat
