LBN 576 (also known as Abell 85, CTB 1, Popped Balloon, Medulla, Garlic Head)

Click on the image for the high-resolution version. MOUSE OVER for the starless HOO view.
High-res links: Stars+Nebulae HOO , Nebulae only HOO ,  H-alpha starless , OIII starless.
LBN 576 is a supernova remnant in Cassiopeia, about 3° north of Caph. Its shape is almost perfectly circular except for a small “open” section. The OIII emission is instead quite asymmetric, mainly concentrated on the western side.

This nebula is catalogued under several names, all commonly used: Abell 85 and CTB 1. It also goes by multiple nicknames, such as Popped Balloon (due to the circular shape with a small opening), Medulla (because it resembles a human brain and medulla), and Garlic Head (for its bulb-like form). To me, “Popped Balloon” is by far the clearest nickname, even though I personally prefer using its LBN catalogue number.

This image was captured on a very windy night at Capanne di Cosola (Italy), and the details were badly degraded. I am honestly not happy with the result because many fine structures normally visible in similar images are missing. I am publishing it anyway as a reminder of how important a wind-protected site and good seeing conditions are. Moreovet it was the first light of my ASI 6200 MM camera on a dark mountain sky!

The nebula was processed in HOO (bicolor: Ha + OIII), while the stars were added from RGB data.
The workflow is similar to my previously published images (CTA 1 and the California Nebula , see the former for an in-depth explanation): StarNet++ for star removal in the narrowband channels, NoiseXterminator for noise reduction (thanks to Emmanuele Sordini!), and finally the addition of stars captured with short RGB exposures.
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Technical Data
Optics TEC 140
Focal Length
 1011 mm
Focal Ratio f/7.2
Exposure Time Total 5 h 20 min, composed of Ha-OIII-RGB 140:130:15:15:20 min (10 min subs for Ha and OIII, 5 min for RGB)
CCD ZWO ASI 6200 MM @-15°C bin 1x1 (processed at bin 3×3 due to very poor seeing)
Location Capanne di Cosola, "prato di Sanremo" (AL, Italian Apennines), altitude 1500 m
Date
 13 October 2023
Mount Gemini G-41
Tracking ZWO ASI 174 mini on an 80mm f/5 refractor
Temperature and humidity T= +10 °C, RH=100 %
Sky brightness at zenith (with SQM-L) 21.2 mag/arcsec^2
Notes Image acquisition with SharpCap

Below are a few additional shots from the field

My setup ready for the night, with some annoying clouds that fortunately disappeared about an hour after astronomical darkness began.


First light for my ZWO ASI 6200 MM, bought used from my friend Antonio Agnesi (thank you!).


A detail of the power system: three large 100 Ah lead-acid batteries inside the car, connected with a heavy 6 mm² red-black cable.
 

A closer view of the three batteries on the passenger seat, wired in parallel using this “ideal parallelator” built around 2010 by my friends Angelo Besani and Marco Moggi.
Total actual capacity: about 220 Ah at 12 V (~2640 Wh).
The yellow box is a VALogger, made by the same friends, recording power consumption throughout the entire night.


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