Spaghetti Nebula, two-panel SHO mosaic with RGB stars

This is a two-panel mosaic of Siemeis 147, AKA Sharpless 2-240, affectionately known as the “Spaghetti Nebula”. The Spaghetti Nebula is a striking astronomical object located in the constellation of Taurus. This ethereal cloud of gas and dust appears as a delicate, curved nebula with intricate filaments that evoke the image of twisted pasta.

When viewed through a telescope or binoculars, the Spaghetti Nebula measures approximately 4’ x 1’, making it a relatively compact object in the night sky. Its distance from Earth is estimated to be around 3,000 light-years away, providing astronomers with a unique opportunity to study its composition and evolution. One of the most intriguing aspects of this nebula is its complex structure, which suggests that it may have originated as a supernova remnant (SNR), resulting from the collapse of a massive star or the interaction between multiple stars. The Spaghetti Nebula’s delicate filaments appear to be in the process of dissolving, a phenomenon known as “dissipation,” where the gas and dust are being eroded away by the intense radiation and strong stellar winds emanating from nearby stars.

Two-panel SHO mosaic of the Spaghetti Nebula

Acquisition Details

• Mount: Astro-Physics Mach2GTO
• Telescope: Takahashi FSQ-106EDXv4
• Camera: ZWO ASI6200MM

The data for this was captured over eleven different nights in January, February, and March, 2025, for a total of 42 hours of data for both panels.

Per-filter totals:

• Panel 1, the lower half
  • Red: 2.42 hours (29 subs)
  • Green: 2.42 hours (29 subs)
  • Blue: 2.42 hours (29 subs)
  • Sii: 3.67 hours (22 subs)
  • Ha: 4.00 hours (24 subs)
  • Oiii: 4.17 hours (25 subs)
  • subtotal: 19.08 hours (158 subs)
• Panel 2, the upper half
  • Red: 3.08 hours (37 subs)
  • Green: 3.08 hours (37 subs)
  • Blue: 3.08 hours (37 subs)
  • Sii: 4.67 hours (28 subs)
  • Ha: 4.50 hours (27 subs)
  • Oiii: 4.50 hours (27 subs)
  • subtotal: 22.92 hours (193 subs)
• total: 40 hours (451 subs)

Processing Overview

All processing was done in PixInsight, using several plugins and scripts.

RGB filters

The processing included (see the updated processing icons here): (this process was repeated for each panel)

• For each of the RGB channels:
  • Dynamic Crop
  • GradientCorrecton
  • BlurXTerminator (correct only)
• RGB combination via PixelMath
• Auto Linear Fit
• ImageSolver
• SpectrophotometricColorCalibration (PhotonFlux)
• BlurXTerminator (full)
• NoiseXTerminator

Narrowband Filters

(this process was also repeated for each panel)

• For each of the individual Ha, Oiii, and Sii master images:
• BlurXTerminator (full)
• GradientCorrection
• NoiseXTerminator

Combination

At this point I had two different sets of four linear images to combine (one set for each panel):

• RGB
• Sii
• Ha
• Oiii

Building the mosaics

To build the mosaics, I needed to use the MosaicByCoordinates script. First, however, I had to plate solve the images. Because I was careful, each set of frames for the respective panel were the same, so I just plate solved the RGB image then applied the astrometric solution to the corresponding narrowband frames by entering this in the process console’s command bar:

cpast -s=RGB Sii Ha Oiii

I performed the MosaicByCoordinates against each panel’s frames (RGB 1 & 2, etc), and ended up with:

• RGB_panel_1_ra.xisf
• RGB_panel_2_ra.xisf
• Sii_panel_1_ra.xisf
• Sii_panel_2_ra.xisf
• Ha_panel_1_ra.xisf
• Ha_panel_2_ra.xisf
• Oiii_panel_1_ra.xisf
• Oiii_panel_2_ra.xisf

These aligned frames themselves were about 4GB of data.

Once that was done I used GradientMergeMosaic for each pair, then continued on with post processing.

Post Processing

• StarXTerminator on each of the four frames, needing only the narrowband starless frames and the RGB stars
• Manually used GHS to stretch the individual narrowband frames
• SHO combination with PixelMath
• AutoLinearFit on the SHO
• Several hours of masks, GHS, curves, and HistogramTransformation to get something I liked
• Stretched the RGB stars via SetiAstro’s “Star Stretch” (stretch: 6, color boost: 0)
• SetiAstro’s Stretched
• PixelMath to screen the RGB stars back on the SHO
• A couple iterations of DarkStructureEnhance to get it to pop
• And, of course, more time with GHS, Curves, and friends

In the end this was a 9131x8615 image (downsized here), and the processing really taxed my machine. The final XISF itself was almost 1gb.

Click an image to see it bigger with some acquisition info

Image details on Astrobin

Spaghetti Nebula