The Eight-Burst Nebula

Designation:  NGC 3132, Caldwell 74, in the constellation of Vela.
Visual magnitude:  +9.7
Apparent size: 1.0 x 0.7 arc-minutes.
Diameter: 0.7  light years.
Distance: 2,300 light years.

The most beautiful objects in the sky are Planetary nebulae, at least in my opinion – partly because each one is different.

They are formed when an expanding shell of ionised gas is ejected from from a class of late-life, low-mass stars which become red giants.

Near the centre of the nebula lies the star which originally shed the gases which formed the nebula. However it is not the bright over-exposed 10th magnitude star visible in my image but a much dimmer 16th magnitude white dwarf star, too close to the brighter star to be seen.

The Hubble Space Telescope picked it out.

The ultra-violet light from this white dwarf is also responsible for causing the gas to glow.

It is my understanding that the light blue and green gas is OIII. The yellow and red are H-alpha and NII.

The unusual name of the Eight Burst Nebula comes from the discovery (in better telescopes than mine) that there are shells of gas from eight separate outburst events.

Planetary Nebulae are short-lived, only existing for a few tens of thousands of years – and because of this, the number of known planetary nebulae in our galaxy is quite small, about three thousand.

In a few billion years, our Sun too will become a red giant, before emitting a planetary nebula and condensing into a hot white dwarf.

Like most planetary nebulae (with some exceptions), the apparent diameter of the Eight Burst Nebula is very small – in this case a mere single arc-minute (one sixtieth of one degree).

As a consequence the image is heavily cropped.


Social Isolating

“Social distancing” is a good idea but it’s not good enough for people with the highest vulnerability to covid-19. 😕

So, I made a joint decision with my Bride not to attend any Society events such as field nights, public nights or meetings until the corona virus is under control. For the rest of this year I will only be imaging from suburban skies at home.

A hard decision, yet an easy one – even if suburban light pollution and unrestrained nearby council street light leave my sky at a disadvantage.


Featured Image Details
Date:  2020-03-13Exposure:  28x214s = 100 min.
Sky brightness (e/pix/sec): 0.93Gain setting:   10
Camera: ZWO ASI 071 MC ProType: CMOS 28.4mm 16 Mpx
Location:  outer suburban.Conditions: clear, late Moonrise.

My images are captured with Sharpcap-pro software using the live-stacking feature, with in-field image processing. Image post-processing is carried out using GIMP freeware.

The image was cropped.

Follow this link to see my image with Astrometry.net annotated overlay.


Telescope Details
SkyWatcher Esprit 120 mm apochromatic 3-element refractor.
840 mm focal length @ f/7 with field flattener.
Baader L-Booster UHC-S light pollution filter 2458276.
SkyWatcher EQ6-R Pro mount, with a polar error of 00′ 08″
ZWO ASI120 guide camera, using PHD2 software.
QHYCCD PoleMaster polar aligning camera.
2018-03-10 Telescope & Roger
Images © Roger Powell
I’m one of the founder members of Macarthur Astronomical Society, Australia. 🙃

Geek Log
[ZWO ASI071MC Pro]
Debayer Preview=On
Pan=0
Tilt=0
Output Format=FITS files (*.fits)
Binning=1
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=80(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=10
Exposure=214
Timestamp Frames=Off
White Bal (B)=99
White Bal (R)=60
Brightness=8
Temperature=-11.1
Cooler Power=100
Target Temperature=-15
Cooler=On
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Anti Dew Heater=On
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
Black Point
Display Black Point=0
MidTone Point
Display MidTone Point=0.5
White Point
Display White Point=1
TimeStamp=2020-03-13T13:01:38.0855495Z
SharpCapVersion=3.2.6173.0
TotalExposure(s)=5992
StackedFrames=28

9 Comments

  1. I agree the nebulae are varied and gorgeous. The social distancing thing is disrupting a lot of lives. We did our part yesterday by going for a lengthy trail hike.

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  2. You and your Bride are wise about the virus issue. We are doing it the same here in Canada too Hopefully I will still be able view you posts as usual.
    Fran

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    1. That is correct. I do not use deliberately use false colours , as you would expect from radio, infra-red, ultra-vilolet or X-ray images. However, not all visible light cameras record identically. The result depends on the chip characteristics.
      In the Hubble image which I linked to in the text, the colors were chosen to represent the temperature of the gases, so are slightly different to mine.

      Liked by 1 person

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