In search of an interesting new astronomical target, I’ve imaged the recently discovered Theta Muscae Supernova Remnant (SNR) G304.4-3.1.

Positioned south of the celestial equator, within RCW 75 (GUM 48a) this remarkable phenomenon presents a compelling target, particularly for those in the southern hemisphere. θ Muscae (HD113904) the central star in the frame, is a variable and double hypergiant star in the constellation of Musca, mag 5.51

As far as I know, this is only the third high-resolution image of the Theta Muscae Supernova Remnant, the first being published by @Bray Falls

Capturing data of this particular target from my Bortle 6 backyard proved to be an immense challenge, compounded by the presence of Light Pollution and the glare of a persistent full moon. However, it was an excellent trial for my recently acquired Atik APX60 CMOS camera paired with a 3nm Chroma Filter.

To combat the adverse conditions at home, I had to shorten the exposure time per NB sub to a mere 5 minutes and accumulate a substantial number of shots—over 300 in total—over a two-week period. Subsequently, I carefully sifted through the data, discarding approximately 20% of the frames due to Moon & LP. This was quite the processing challenge as this thing is really faint!

Additionally, I obtained RGB data from a friend’s Bortle 3 rural property to enhance the overall quality of the image with some nice colourful stars.
You can see all my gear set up in the country to image RGB stars this target here.


Capture Details

TelescopeTakahashi TOA 130 with TOA-35 Reducer
CameraAtik APX 60
MountIoptron CEM70G
FiltersChroma RG&B, 5nm Ha, 3nm O3
Guiding CameraZWO ASI 290 mini
Integration time (Exposure)27.0 hrs
LocationMelbourne, Victoria, Australia
DateMarch, 2024

About this Nebula

In his description, Bray Falls states, “The bright blue star cradled by this nebula is theta Muscae, a very bright wolf rayet star. These are stars nearing the end of their life, and they are commonly associated with beautiful nebulae, like the crescent nebula or Thor’s helmet.

In 2009 a group of scientists sought to understand if this nebula was associated with Theta Muscae. You can read their paper here. They determined that this area was likely an ancient supernova remnant, plus some random Hii regions. They only studied the area in Ha, I’m not sure if they were aware of the Oiii structure present. It just so happens that the remnant is in the perfect spot to ‘fake’ itself as a wolf rayet nebula, a curious cosmic alignment.

I first studied the region this April and noted a very bright and interesting Oiii structure in the region. After some digging, I found @Mathew Ludgate  had noted this some years prior in this image. Both of us used camera lenses with not much resolution. I figured this area would be worth a high-res follow-up, and boy was I right! The structure is more insane than I could’ve imagined. Not to mention this thing is HUGE. This high-resolution image definitely points towards this nebula being a supernova remnant.” © Bray Falls.

Theta Muscae SNR

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This is only the third high-resolution image published of the Theta Muscae Supernova Remnant, to my knowledge.

- Andy Campbell