October 20, 2026

My Image of the SH2-134 region in Cepheus.

🔭 Project Summary

Target: Sh2-134 / Sharpless 134 / LBN 490 — emission nebula complex around Lambda Cephei

Capture Dates: September 6, 11, and 14, 2026

Constellation: Cepheus • Distance: Approximately 2,900 light-years for Sh2-134

Type: Wide-field emission nebula complex with glowing filaments, dark interstellar clouds, and the hot supergiant Lambda Cephei

Imaging Period: September 6–14, 2026 • Total Integration: 17 h 52 m 00 s (SHO narrowband + RGB stars)

Filters: Ha · OIII · SII (Astronomik 36 mm 6 nm) + R · G · B (ZWO 36 mm LRGB Gen II)

Telescope: Askar FRA400 72 mm f/5.6 Quintuplet Air-Spaced Astrograph

Camera: ZWO ASI2600MM-Pro (−15 °C; Gain 100 narrowband, Gain 0 RGB)

Mount: ZWO AM5 on custom steel pier

Processing: PixInsight (SHO narrowband + RGB stars) & Photoshop

Location: Whispering Skies Observatory · Honeoye Falls, NY (USA)

Acquisition Notes: Ha: 68 × 300 s; OIII: 67 × 300 s; SII: 75 × 300 s; R: 14 × 30 s; G: 15 × 30 s; B: 15 × 30 s, all bin 1×1 at −15 °C. Total integration after culling bad or questionable frames: 17 h 30 m narrowband + 22 m RGB.

Image Note: This wide-field SHO narrowband image explores the rich region around Sh2-134 and Lambda Cephei, including the compact emission nebula Sh2-135, numerous Lynds bright and dark nebulae, and Barnard dark clouds such as B169, B170, B171, B173, and B174.

Table of Contents Show (Click on lines to navigate)

Back To Top

Special Note

Welcome to the New Image Processing Page for this project! You got here by following a link in the main Image Project Report, and you can easily return to that by using the back button on your browser.

Abbreviations Used

ACM Astro Color Mixer Script

ACE Astro Contrast Enhancer Script

ASL Astro Star Lab - Prototype tool

ATR Astro Tone Recovery - Prototype tool

BXT BlurXTerminator by RC-Astro

CC Cosmetic Correction

CT Curves Transformation Process

DBE Dynamic Background Extraction Process

ET Exponential Transformation

HT Histogram Transformation

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

🔭 Sh2-134 SHO + RGB Stars Processing Flow

High-level sequence from frame review and WBPP integration through separate nebula and RGB-star processing, masked color refinement, highlight recovery, Astro Star Lab repair and recombination, and final Photoshop output.

1. Blink Review and Frame Culling

Review Lights Inspected all six channels for dew circles, stellar halos, clouds, and tracking problems

Cull Affected Frames Removed 6 Ha, 5 OIII, 7 SII, 7 R, 7 G, and 8 B frames; camera-heater issues made dew the main concern

Check Calibration Frames Darks, dark flats, and flats passed inspection; retained 17 h 52 m of light-frame integration

2. WBPP 3.01 Calibration and Integration

Load and Configure Loaded lights and calibration frames; selected maximum quality, automatic reference and pedestal, CosmeticCorrection, and autocrop

Match Exposure Groups Set dark and light exposure tolerances to zero for precise calibration grouping

Integrate Six Channels WBPP completed in 37 minutes 16 seconds with no errors

3. Construct SHO and RGB Masters

Prepare Masters Loaded and renamed the integrated Ha, OIII, SII, R, G, and B images

ChannelCombination Built the SHO nebula image and a separate RGB image for natural star colors

4. Process the Linear SHO Image

DBE Background Correction Placed background samples to avoid strong nebulosity

Correct and Refine with BXT Applied correct-only mode, measured stars at X = 2.49 and Y = 2.32, then ran full BlurXTerminator with enhanced star-shrinking settings

Denoise and Remove Stars Applied NoiseXTerminator V3, then StarXTerminator; discarded the SHO stars in favor of RGB stars

5. Prepare the Linear RGB Stars

DBE and BXT Correction Subtracted the RGB background and used BXT correct-only to improve stellar shapes and reduce some flare artifacts

SPCC Color Calibration Used a background preview, the Ideal curve, and ZWO R, G, and B filter curves

Refine and Extract Stars Measured X = 1.92 and Y = 1.81; applied full BXT at approximately 4.0, NXT V3, and SXT; retained the RGB stars for later stretching

6. Stretch the Starless SHO Image

STF → HT Stretch Transferred the ScreenTransferFunction stretch to HistogramTransformation to take the starless SHO image nonlinear

7. Build Masks and Establish Color Balance

Warm and Cool Masks Created ColorMask selections at hues 328–68 and 162–259, both with blur 5; boosted each mask with CurvesTransformation

Reduce Green and Magenta Applied SCNR Green at 0.85, inverted, repeated SCNR, and inverted back

Set Tone and Color Adjusted CurvesTransformation, then applied another SCNR Green pass at 0.85 to address remaining green

8. Refine the Starless Nebula

Masked Color Adjustments Used the warm and cool masks with CurvesTransformation to tune color and saturation separately

Curves and Astro Color Mixer Darkened the overall tone, refined cool colors, and reduced warm-color brightness

Astro Tone Recovery Recovered compressed highlight detail in the bright orange regions using the prototype tool

Additional Noise Reduction Tried another NXT pass; improvement was limited in the weak-signal areas

Gentle Contrast Enhancement Applied a small amount of ACE Clarity and Dehaze; avoided Texture adjustments because of visible noise grain

Final Starless Color Polish Refined orange tones with ACM, darkened with Curves, then used targeted Photoshop selections for color mixing and curve adjustments

9. Stretch, Repair, and Recombine RGB Stars

Astro Star Lab Analysis Loaded the RGB stars-only image into the prototype tool for analysis and an initial stretch

Preview Against the Nebula Added the processed starless image and adjusted star presence and color saturation

Review Flagged Stars Inspected approximately 60 flagged bright stars, mostly showing residual dew-related flare artifacts; reviewed automatic repairs and approved suitable results

Output the Composite Combined the refined RGB stars with the processed SHO nebula

10. Photoshop Finishing and Publication

Export 16-bit TIFF Saved the composed image as a 16-bit unsigned TIFF for Photoshop finishing

Crop and Add Watermarks Trimmed the less-interesting left edge while retaining the full image height; added presentation watermarks

Export Final JPEGs Created clear, watermarked, and web-sized versions for publication and sharing

Processing this Image

(All Processing is done in PixInsight, with some final touches done in Photoshop)

1. Blink

General
- Lots of satellite tracks - easy to handle
- Somehow the camera dew heater was not enabled for a couple of nights, and we had very heavy dew. Frames were rejected due to dark dew circles (see below) and halos on stars.

Ha
- 6 frames removed: 4 for dark dew circles, and 2 for clouds. One image had a plane go through it, and I left it in.
OIII
- 5 frames removed for dew.
SII
- 7 frames removed: 2 for tracking, 5 for dark dew circles.
Red
- 7 removed for dew circles.
Green
- 7 removed for dew circles.
Blue
- 8 removed for dew circles.
Darks
- All frames looked suitable.
Dark Flats
- All frames looked suitable.
Flats
- All frames looked suitable

2. WBPP 3.01

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 (this was not needed)
Set for Autocrop
WBPP ran for 37:16. No errors.

3. Load Master Images and Create Color Images

Load all master images and rename them.
Using ChannelCombination, create the Master SHO and RGB color images

4. Initial Processing of the Linear SHO data

Run DBE, adjusting the sampling plan to avoid dense nebulosity.
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 PSFImage script to measure star sizes. X = 2.49 Y = 2.32. This will influence the values used in BXT.
Run Full BXT - I am using the default terms for BXT for the stars. See the BXT Panel Snapshot below.
Run NXT V3 - see params from snapshot below.
Run SXT and don’t save the SHO stars. I will be using RGB stars, so there is no need to keep them.

Before BXT

BXT Correct Only

BXT Full.

Master SHO Before BXT Correct Only, After BXT Correct Only, After BXT Full, After NXT

Master SHO Starless Image (click to enlarge)

5. Process the Linear RGB Data

Run DBE for the RGB linear image. Use subtraction for the correction method. Choose a sampling plan that avoids the nebulae (see below)
Run BXT - correct only. This cleans up the stars at the corners. It also cleaned up a lot of the weird star flare that I had - but not all of it.
Select a preview rectangle that samples the background sky, and then set up and run SPCC.
- Use the Ideal curve
- Use ZWO R, G, & B filter curves,
Run the PSFImage script to measure star sizes. X = 1.92, Y = 1.81. 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 double the measured star sizes. I failed to capture a screenshot of the BXT panel and the BXT series, but I used a value of about 4.0 to clean up the star images
Run NXT V3 - see params from snapshot below.
Run SXT and don’t save the RGB starless image.

Final Master RGB image - Before Star Removal.

6. Keep the RGB Stars Nonlinear - For Now…

At this point in the process, I would stretch my stars and then take them nonlinear. Now I leave them linear, then stretch and combine the stars and starless images at the end of the process using my Astro Star Lab tool.

7. Take the Starless SHO Image Nonlinear

Use the STF→HT method to take the SHO starless Image nonlinear.

8. Process the Nonlinear SHO Starless Image

This is the big meaty step of this process. In this section, I will focus on getting Green and Magenta under control, nailing the tone scale and color separation, doing masked warm/cool refinement, and then ACM/ACE polish.

Create the WarmMask
- Use the ColourMask Process with a Start Hue of 328 and an end hue of 68, with a blur of 5
- Apply CT to boost the mask
Create the CoolMask
- Use the ColourMask Process with a Start Hue of 162 and an end hue of 259, with a blur of 5
- Apply CT to boost the mask
Apply SCNR Green at 0.85 to reduce green in the image.
Invert the image (make magenta regions look green)
Apply SCNR Green at 0.85 to reduce the amount of green in the image.
Invert the Image
Apply CT for Tone and Color.
Apply SCNR for Green at 0.85. There was still too much green after the CT adjustment, so now it looks much better.
Apply the Warm Mask
- Apply CT to adjust color and saturation
Apply the CoolMask
- Apply CT and adjust cool-color saturations
Apply a global CT to darken
Use ACM to fine-tune the Cool colors and darken the Warm colors
The orange areas have some highlights that look a little compressed, so I used my Astro Tone Recovery tool to pull back some compression in the highlights and emphasized the recovered detail there as well.
Then I did another NXT run. (params used can be seen below) The weak-signal areas have a lot of noise, and NXT has already done what it can, so this step didn't add much, but I figured it was worth another pass.
Because of the noise grain in the image, I wanted to go super light with ACE to enhance contrast. Just a smidge of Clarity and Dehaze helped, but I stayed away from Texture adjustments.
Do another ACM adjustment focusing on the orange colors.
Do a CT to darken.
Export the image to Photoshop and do some targeted Lasso color mixer and curve work.
Save the Photoshop-adjusted starless image and reopen it in PixInsight for star recombination.

9. Add the Stars Back In

Using the prototype Astro Star Lab Script, run it with the RGB Stars-only image.
Once the app finished the analysis and created the initial stretch, I added the starless image and assessed the stars' look.
These look a little weak to me, so I played with the star presence and color saturation sliders to get the look I liked.
Then I looked at the stars that the analysis had flagged. Most of these were the flare problems that I assume are dew-related. About 60 of the brighter stars had been flagged. I then let the automatic fix take a crack at fixing them and approved the ones that looked good.
Stars were then fixed.
Finally, I had the tool output the composed star and starless image.

The background starless image has been added back in.

The stars looked a little weak so I boosted the presence and color boost

Example of a repaired star. The flare artifacts in this overlapping group of stars have been reduced.

10. Export the Image to Photoshop for Polishing

Save the image as a 16-bit unsigned TIFF and move it to Photoshop
I changed the final image's aspect ratio to 7:5 so I could clip off the left side, which was a little boring, without losing anything at the top or bottom. Added Watermarks.

Exported Clear, Watermarked, and web-sized JPEGs.

11. The Final Image!

12. Final Comments

This is a complex field with both very faint and very bright sections, which made it a challenge to process. The star issues were also a challenge. Luckily, I was creating a script to handle stars, so I could use that platform to minimize the impact of the dew-related flare issues. I just wish I had another 12-15 hours of integration to really bring out those faint details with less noise!

Back to the Main SH2-134 Region 2026 Page

Alternatively, you can use the back arrow to return to the Main SH2-134 Region page, or use the menu at the top of the page to continue navigating.

Thanks,

Pat

The SH2-134 Region of Cepheus 2026: Image Processing Walkthrough