ASTRO:
     type=Supernova remnant
     const=Auriga / Taurus
     mag=(unk)
     dist=3000 ly
     size=160 ly
IMAGE:
     location=EB Driveway
     BrtlCls=4
     moon=21%(avg) WxCr
     exposure=CMOS OSC 4x49x360s 2x2 mosaic, (4.9h avg ea. panel)
     palette="HOO"
EQUIPMENT:
​     optics=ES102CF APO / Starizona "L" 0.65x rdcr, FL(eff.)=464mm, f(eff.)/4.55
     camera=ZWO ASI2600MC-Pro
     filter=Radian Triad Ultra quad narrow-band
     mount=Celestron AVX EQ
     guiding= Orion 60x240mm, ZWO ASi244MC
SOFTWARE:
     acquisition=Stellarium, APT, PHD2
     processing=PixInsight (RCAstro), Photoshop (Lumenzia, APF-R), LrC

It's easy to get lost following the intricate filaments in this detailed mosaic image of Sharpless 2-240 (or Sh2-240), also known as Simeis 147.  Its common name is the "Spaghetti Nebula".  It is a very faint supernova remnant (or SNR) catalogued as No. G180.0-01.7.   Located inside our home Milky Way galaxy, it stands in planet Earth's sky almost exactly opposite the galactic center, straddling the border between the constellations Auriga and Taurus.  It was discovered in 1952 at the Crimean Astrophysical Observatory by Grigory Shajn and his team using a Schmidt camera and a narrow band filter tuned closely to the Hydrogen Alpha light wavelength spectral transmission line.

This discovery was part of a sky survey conducted between 1945 and 1955, most likely using equipment captured from Nazi Germany during WWII, as the observatory was practically destroyed during the war.  The Schmidt camera had a very narrow field of view of 175' (arcminutes).  Many previously unknown hydrogen nebulae were discovered this way, as they are not readily visible in regular, broad-band photographs.

The nebulous area has a huge and almost spherical shell with a filamentary structure.  With a visual apparent diameter of approximately 3 arc-degrees, it is appx six (6) times the diameter of our full Moon.  At an estimated distance of 3000 light-years, its calculated diameter is nearly 160 ly.  It is estimated to be 40,000 years old, meaning light from the massive stellar explosion first reached Earth 40,000 years ago.

But the expanding remnant is not the only aftermath...  The cosmic catastrophe also left behind a rapidly spinning neutron star known as pulsar PSR J0538+2817 inside the nebula core.    Discovered in 1996, it stirred great interest among the scientific community when it was found to be physically linked to the supernova remnant.  That pulsar is emitting a strong signal in the radio spectrum of electromagnetic spectral bandwidth.  It rotates at a frequency of 143ms per rotation (...or appx 7 times per second).

IMAGER'S COMMENTS:​The Spaghetti is difficult to observe because it is extremely faint.  But also because of its enormous size, amateur imagers sometimes struggle encompassing the entire formation into a single framed image.  The object can be mostly captured using standard photographic lenses 200mm or shorter.  Alternatively, and as done here, imagers using longer focal lengths can opt to use a "mosaic" technique, capturing multiple frames from across the object's profile, and then 'stitching' them together to capture the entire structure.  This sharp composite image includes data captured using a quad narrow-band filter and processed in the "HOO" palette to highlight the faint red emission from hydrogen atoms and blue emission from oxygen atoms tracing the shocked, glowing gas.

231218 - Sh2-240 "Spaghetti" nebula