NGC3372 Eta Carina Nebula

NGC3372 Eta Carina Nebula, captured from Atacama Lodge, San Pedro de Atacama, Chile on 6 March 2024

Fun facts

The Carina Nebula or Eta Carinae Nebula (catalogued as NGC 3372; also known as the Great Carina Nebula) is a large, complex area of bright and dark nebulosity in the constellation Carina, located in the Carina–Sagittarius Arm of the Milky Way galaxy. The nebula is approximately 8,500 light-years (2,600 pc) from Earth

The nebula has within its boundaries the large Carina OB1 association and several related open clusters, including numerous O-type stars and several Wolf–Rayet stars. Carina OB1 encompasses the star clusters Trumpler 14 and Trumpler 16. Trumpler 14 is one of the youngest known star clusters at half a million years old and contains stars like the O2 supergiant HD 93129A. Trumpler 16 is the home of many extremely luminous stars, such as WR 25 and the Eta Carinae star system. Trumpler 15, Collinder 228, Collinder 232, NGC 3324, and NGC 3293 are also considered members of the association. NGC 3293 is the oldest and furthest from Trumpler 14, indicating sequential and ongoing star formation.

The nebula is one of the largest diffuse nebulae in our skies. Although it is four times as large as and even brighter than the famous Orion Nebula, the Carina Nebula is much less well known due to its location in the southern sky. It was discovered by Nicolas-Louis de Lacaille in 1752 from the Cape of Good Hope.

The Carina Nebula was selected as one of five cosmic objects observed by the James Webb Space Telescope, as part of the release of its first official science images. A detailed image was made of an early star-forming region of NGC 3324 known as the Cosmic Cliffs.

Eta Carinae is a highly luminous hypergiant star. Estimates of its mass range from 100 to 150 times the mass of the Sun, and its luminosity is about four million times that of the Sun.

This object is currently the most massive star that can be studied in great detail, because of its location and size. Several other known stars may be more luminous and more massive, but data on them is far less robust. (Caveat: Since examples such as the Pistol Star have been demoted by improved data, one should be skeptical of most available lists of “most massive stars”. In 2006, Eta Carinae still had the highest confirmed luminosity, based on data across a broad range of wavelengths.) Stars with more than 80 times the mass of the Sun produce more than a million times as much light as the Sun. They are quite rare—only a few dozen in a galaxy as big as ours—and they flirt with disaster near the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in its radiation and gas, resulting in a possible supernova or hypernova in the near future.

Eta Carinae’s effects on the nebula can be seen directly. Dark globules and some other less visible objects have tails pointing directly away from the massive star. The entire nebula would have looked very different before the Great Eruption in the 1840s surrounded Eta Carinae with dust, drastically reducing the amount of ultraviolet light it put into the nebula.

Distance: 8500 light years
Apparent magnitude: +1.0
Apparent dimensions: 2°x2°
Constellation: Carina
Designations: NGC3372, ESO 128-EN013, GC 2197, h 3295, Caldwell 92

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Capture & Processing Notes

This was my first image captured during my long-planned and much-anticipated trip to San Pedro de Atacama, Chile – for an opportunity to see and photograph the Southern Hemisphere targets that can’t be seen from the Northern Hemisphere. Upon arrival at the Atacama Lodge in San Pedro de Atacama, Chile (after approximately 32 hours of travel), although I was a bit exhausted and debated, I didn’t want to miss the opportunity of a clear night – especially since the forecast called for clouds throughout rest of the nights after the first. I was choosing to ignore that horrible prediction, but didn’t want to risk it, so I set about getting the gear set up in the area behind (to the east) of Atacama Lodge #1, while Danita went to get some groceries.

I got everything set up, got all the RST-135 mount’s new location activities accomplished, and started on the process of finding the Southern Hemisphere pole star (Sigma Octantis) just as dusk was setting in.  Even though I had researched what to look for, watched videos on the process in Polemaster, it was still a very difficult process, as the pole star is very faint.  When Danita returned from her grocery adventure, she came out to help.  The two of us struggled for a couple of hours, until finally, I decided – since this was THE crucial first step in having this trip meet its objective of photographing the Southern Hemisphere objects – I was going to go and ask Alain Maury (the Atacama Lodge owner) for help.  He was at the observatory across the way from our lodge, grabbed his laser pointer (a VERY powerful laser pointer) and a pair of binoculars to come and save the night.  He did just that!! Alain easily pointed out the pole star and pointed the mount so that it and those that need to be in the polar alignment template were in the center of my Polemaster screen – allowing me to polar align the mount and get on with the night’s imaging.  Whew!! Trip disaster averted – THANK YOU Alain!

The other issue that I ran into was the mount returning to “home” throughout the night to its Northern Hemisphere home position (pointing west).  I continually used the hand controller to put it into the correct home position before starting any sequence.  Got the sequence going – the plate solving and autofocus worked well, the  autoguider struggled to resume after pausing for the autofocus, then the plate solving was all star traily.  Reboot, shut everything down, and start again (yes, Danita stayed out there for the entire show!) finally got the sequence going at about 2300. 

The errant home position issue came to haunt me a little bit during the meridian flip.  Once I did the meridian flip (which was successful) and the sequence began, I decided to wait for one subframe to capture to make sure everything was going to work out well.  I was faced with a “would you like to pause for the meridian flip” prompt!  I selected “yes” – wrong answer – had to abort and start anew.  Second time, same thing – I said “no” and the sequence continued.  But, I was a little spooked that I was going to get prompted every 5 minutes for the rest of the night, so I aborted, turned off auto-meridian flip and started over again.  That worked – no more prompts and successful collect for the rest of the night.

I stacked the images in APP each morning to check on the capture.  I waited on further processing until I was home with the full suite of software on “BeersAPStation” work station – but was very encouraged with the first night’s data (and the telescope has not been moved, so we should have a quicker start on night #2!).

Sequence Plan:

  • Sequence plan: Gain: 158, Temp: -0°C, offset=30; 85x5min; Total exposure time: 425 minutes, 7:05 hours.
  • Captured: 6 March 2024 (6Mar2024, 2308 Chilean Daylight Time (CDT) – 7Mar2024, 0637CDT);
  • Shooting location: Atacama Lodge, San Pedro de Atacama, Chile

Processing summary: Captured with SGP. Stacked in APP. Star removal with Starnet++. Processed in LR/PS


All equipment controlled by HP Probook (DSO CTRL 1) Windows 10 laptop running Sequence Generator Pro v4.3.0.1305.  

  • Polar alignment: QHYCCD camera (controlled by Polemaster for polar alignment)
  • Imaging: (Southern Cross) Askar FRA600 on Rainbow Astro RC-135E, ZWO ASI2400MC#1 camera
  • Autofocuser: ZWO EAF ( Electronic Automatic Focuser)
  • Mount: Rainbow Astro RST-135E (controlled by iHubo ASCOM driver)
  • Autoguiding:  Orion 60mm Multi-Use Guide Scope with Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (controlled by PHD2)