NGC 5128 - Processing Centaurus A, our first southern sky object from an observatory in chile

Updated: Aug 18


We’ve always wanted to do astrophotography from the Southern Hemisphere. We never had the chance to visit the Southern part of the globe and don’t think we’ll be able to for a while, so the best thing we could possibly do in the meantime was to process a Southern object!


We made a new friend on Instagram, Matt Dieterich (@mattdieterich) who kindly allowed us to download some of his raw data of a famous southern galaxy: Centaurus A.

Matt works for Planewave Instruments and is able to image from an observatory in Chile: El Sauce Observatory.

The remote telescope setups are under extremely dark skies, so the files we received all looked very clean with little to no noise!



We'd like to thank Matt for sharing his data, this meant a lot to us and we will not forget our first time processing a deep sky object from the Southern Hemisphere! We hope to be able to image under southern skies in the near future!


Below is the result of our attempt at processing Centaurus A. The raw data we received totaled about 4 hours and 15 minutes in LRGB. You can find all acquisition details under the image.



The beautiful Centaurus A


GEAR USED:

Camera: FLI Proline 16803

Telescope: PlaneWave 24" f/6.5 CDK

Mount: PlaneWave L-600

Observatory: Observatorio El Sauce

Processing: Pixinsight

ACQUISITION DETAILS:

Total Exposure Time: 4.33 hours

Exposure Time per frame: 5 minutes

Filters: L (16)/R (12)/G (12)/B (12)



How to find Centaurus A?

Centaurus A is located 13 million light-years away in the constellation Centaurus (no, really?). It was discovered by James Dunlop in 1826.

NGC 5128 is the 5th brightest galaxy in the night sky, and is visible with binoculars or a telescope. It is extremely difficult to spot with the naked eye, but not impossible under a true dark sky.


Although Centaurus A is a southern hemisphere object, it can also be seen from the northern hemisphere in countries that are close to the equator. For us in Vegas, the constellation can be seen rising just a tiny bit, but not enough to see any deep sky object within it.


NGC 5139 - Omega Centauri

Centaurus A lies pretty close to one of the most famous and impressive star clusters in the sky: the globular cluster Omega Centauri (NGC 5139).


With the right lens, an amateur astrophotographer could frame both objects in the same field of view and capture a pretty epic image.


This is the one cluster we'd love to capture with our own equipment if we ever visit the southern hemisphere.





Cool Facts
  • The galaxy's strange shape is due to some intense jets expelling from the black hole

  • Member of the Virgo Supercluster

  • The fifth brightest galaxy in the sky



Processing of Centaurus A

My favorite type of deep sky object to process is nebulae. I find that galaxies are usually less exciting overall and can sometimes be a little bit more difficult, especially if you need to add some hydrogen alpha data to the workflow.


In this case, I was to work with LRGB channels, and the processing workflow used was pretty basic. You can download our PDF follow-along processing guide that details our entire workflow HERE.


The only challenging part was to deal with the weird, round gradient in the background. I was unable to "fix" this after several attempts and got a bit confused. I started to wonder if there was an issue with the quality of the files, until I realized that this "gradient" was 100% normal and is just light expelling outwards from the galaxy (not the bright, obvious part but very faint light all around the image). I wouldn't have known if I did not look up more images of Centaurus A online. It is very faint, but there nonetheless.


PixInsight: Centaurus A - Broadband channels


Crop on the core of Centaurus A

Before I was done, I revisited the core of the galaxy and worked on making it as crisp and detailed as I possibly could.

This can sometimes be a difficult challenge as noise really starts to become obvious and individual color pixels pop out in a really unrealistic fashion.



Because this data was very clean to start with, I found it pretty easy to bring out the details in the core while keeping the overall image nice and not "overcooked".



What did each broadband channel look like?


Below you can see what the stacked frames look like for each broadband channel. Four filters were used to capture Centaurus A:


  • Luminance (top left)

  • Red (top right)

  • Green (bottom left)

  • Blue (bottom right)


Surprisingly, all four of these channels look very identical. Usually, the luminance filter shows much more detail and brightness than the other three, but not in this case. The only channel that seems to be lacking a little bit is the red!




A Note about the Equipment used

Matt used professional-grade equipment to capture Centaurus A.


Telescope used:

PlaneWave 24" f/6.5 CDK

  • Telescope tube weight: 240 lbs.

  • Focal length: 3962 mm (156 inches)

  • Focal ratio: f/6.5

  • Aperture: 610 mm (24 inches)

  • Image Circle: 70 mm

  • Cost: $55,000


Mount used:

PlaneWave L-600 Direct Drive Mount

  • Computerized Mount

  • Head Design: Hybrid Alt Az/EQ

  • Instrument Capacity: 300 lbs

  • Latitude Range: 0 to 90 degrees

  • Mount Weight: 338 lb

  • Cost: $29,000


Camera used:

FLI Proline PL16803 Monochrome CCD Camera

  • Manufacturer: FLI

  • Model: KAF 16803

  • Pixel Array: 4096 x 4096

  • Pixel Size: 9 microns

  • Sensor Design: Full Frame

  • Sensor Diagonal: 52.1mm

  • Front Illumination

  • Cost: $12,795


The telescope and mount come as a pack, the "CDK 600" as seen on the image below. The camera can be seen on the right image. Click on each picture to read more about these insane products!


The total cost of the entire setup is unknown, but just these three products bring the price to $92,795, making it the most expensive rig we ever had the chance to process data from! Well, we could grab some raw files from Hubble, but we haven't done that yet haha!

Of course, this setup is a permanent observatory installation. Although we'd love to one day own something similar, it is definitely not going to fit in your trunk. You would need a crane just to lift the mount!


Matt has several videos on his YouTube channel showing how his colleagues at PlaneWave instrument and himself install these expensive astrophotography products in observatories around the world or even in the houses of some lucky customers!



Final Thoughts

We are so happy to have been able to work on a southern sky object. This is something we thought would not happen for a couple more years, so we were thrilled when we found someone who was willing to share his data!


We can't wait until we are able to visit a country in the southern hemisphere, and use our own equipment to image the beautiful deep sky objects from the other part of the globe.


Have you captured Centaurus A? Attach your image in the comments and let us know your acquisition details!


Make sure to follow us on Facebook, Instagram, and YouTube to stay up to date with our work!


Clear Skies,

Galactic Hunter





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#CentaurusA #NGC5128 #PlaneWave #Chile #Galaxy #South


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