Dolphin Head Nebula

[rmuhlack (Richard)]

Here is another astro project that I've been working on over the last month or so:

Sh2-308, known as the Dolphin Head Nebula located in the constellation Canis Major.

This nebula is relatively close at a distance of (only) 4530 light years and is composed of ionised hydrogen surrounding the Wolf-Rayet star EZ Canis Majoris (EZ CMa), which is in the brief, pre-supernova phase of its stellar evolution (so sooner or later...BOOM).

Following discovery back in the 1960s that the brightness and spectra of EZ CMa varies over a period of around 3.7 days, there has been debate in the scientific literature as to whether this variation is caused by a companion binary star or by activity on the star’s surface. Most recently, a 2024 study by Barclay and collaborators concluded based on CHIRON spectroscopic analysis that “Instead of the binary system hypothesis, we suggest that EZ CMa is a single WR star with strong co-rotating interaction regions. Such a system is also seen in the well-studied WR star WR 134 …and represents a simpler interpretation of all available observations. “

Ref:
Barclay, K. D., Rosu, S., Richardson, N. D., Chené, A. N., St-Louis, N., Ignace, R., & Moffat, A. F. (2024). Using CHIRON spectroscopy to test the hypothesis of a precessing orbit for the WN4 star EZ CMa. Monthly Notices of the Royal Astronomical Society, 527(2), 2198-2208.

My image of the Dolphin Head Nebula has an exposure time of 22.75 hours, captured across 3 Dec - 7 Jan. The project was not without its challenges. During processing I discovered that somehow when setting up on day 3 I must have slightly rotated the telescope optical tube in its tube rings (when fitting the dew shield perhaps…?), which resulted in the diffraction spikes being rotated (relative to the star field) from day 3 onwards compared to days 1 and 2. I addressed this by processing the starless full stack (from all approved frames across all days) and then combining with stars from a subset of frames that were taken after the tube rotation. Also (somewhat annoyingly) the L-enhance filter has caused some circular reflections around some of the bright stars. But perhaps they add to the drama of the image...? (like lens flare in a JJ Abrams movie haha).

Sharpstar 13028HNT, Skywatcher HEQ5, QHY533C, Optolong L-Enhance, 273 x 5mins, Processed with PixInsight

Astrobin version: https://www.astrobin.com/vfug84/

[strongmanmike (Michael)]

A very nice result Richard and I like the big halos, really makes it look like its namesake

Mike

[gregbradley]

Nice image overall but those halos are a bugger.
Probably caused by a need for more baffling on the
Primary mirror tube.

Originally Posted by rmuhlack

Here is another astro project that I've been working on over the last month or so:

Sh2-308, known as the Dolphin Head Nebula located in the constellation Canis Major.

This nebula is relatively close at a distance of (only) 4530 light years and is composed of ionised hydrogen surrounding the Wolf-Rayet star EZ Canis Majoris (EZ CMa), which is in the brief, pre-supernova phase of its stellar evolution (so sooner or later...BOOM).

Following discovery back in the 1960s that the brightness and spectra of EZ CMa varies over a period of around 3.7 days, there has been debate in the scientific literature as to whether this variation is caused by a companion binary star or by activity on the star’s surface. Most recently, a 2024 study by Barclay and collaborators concluded based on CHIRON spectroscopic analysis that “Instead of the binary system hypothesis, we suggest that EZ CMa is a single WR star with strong co-rotating interaction regions. Such a system is also seen in the well-studied WR star WR 134 …and represents a simpler interpretation of all available observations. “

Ref:
Barclay, K. D., Rosu, S., Richardson, N. D., Chené, A. N., St-Louis, N., Ignace, R., & Moffat, A. F. (2024). Using CHIRON spectroscopy to test the hypothesis of a precessing orbit for the WN4 star EZ CMa. Monthly Notices of the Royal Astronomical Society, 527(2), 2198-2208.

My image of the Dolphin Head Nebula has an exposure time of 22.75 hours, captured across 3 Dec - 7 Jan. The project was not without its challenges. During processing I discovered that somehow when setting up on day 3 I must have slightly rotated the telescope optical tube in its tube rings (when fitting the dew shield perhaps…?), which resulted in the diffraction spikes being rotated (relative to the star field) from day 3 onwards compared to days 1 and 2. I addressed this by processing the starless full stack (from all approved frames across all days) and then combining with stars from a subset of frames that were taken after the tube rotation. Also (somewhat annoyingly) the L-enhance filter has caused some circular reflections around some of the bright stars. But perhaps they add to the drama of the image...? (like lens flare in a JJ Abrams movie haha).

Sharpstar 13028HNT, Skywatcher HEQ5, QHY533C, Optolong L-Enhance, 273 x 5mins, Processed with PixInsight

Astrobin version: https://www.astrobin.com/vfug84/

[rmuhlack (Richard)]

Originally Posted by strongmanmike

A very nice result Richard and I like the big halos, really makes it look like its namesake

Mike

thanks Mike

Originally Posted by gregbradley

Nice image overall but those halos are a bugger.
Probably caused by a need for more baffling on the
Primary mirror tube.

Thanks Greg. A lack of baffles could be partially responsible (this scope isn't baffled, although the tube interior is fully flocked), however I think the L-enhance filter combined with the fast f2.8 is mostly to blame. For comparison, this scope with the same camera and an Optolong UV-IR filter doesn't give halos, even on Alnitak

[gregbradley]

Originally Posted by rmuhlack

thanks Mike



Thanks Greg. A lack of baffles could be partially responsible (this scope isn't baffled, although the tube interior is fully flocked), however I think the L-enhance filter combined with the fast f2.8 is mostly to blame. For comparison, this scope with the same camera and an Optolong UV-IR filter doesn't give halos, even on Alnitak

Reflections off the filter then is clearly the cause.
That’s easier to fix than baffles!

Greg

[CaptainCook (Gary)]

FWIW I like the halos. You get more subtle random (ugly) ones using L extreme but these are more pronounced and in your face making it more dynamic. At the end of the day this is what your equipment captured so be it ..it's no different to diffraction spikes on some and not others. Id be happy with this.

[AlexN]

Beautiful mate, very nice!!

[Ashen (Caleb)]

Absolutely gorgeous