I know, I already did a picture of The Great Carina Nebula, but I never did a picture of Eta Carinae Nebula in a 60 MEGAPIXELS mosaic. You shall forgive me!
The Eta Carinae Star
The Eta Carinae is also the name of the star inside the nebula surrounding it. Whitin a mass of 100 to 150 times the mass of the Sun, this star is HUGE! It also is, probably, a binary star. What does that mean? That there is another star, in this case really smaller than the main star of the system, and also much hotter and with half the brightness. This binary system have a cloud of gas 400 times the size of our solar system, wich once was ejected by its bigger star.
The beautiful Eta Carinae Nebula
But back to the Eta Carinae Nebula! As an emission nebula, it shines mostly it the H-Alpha frequency of the electromagnetic spectrum. In other terms, the color mostly red cames from the atoms of hydrogen element, witch absorbs the UV light from the big blue and young stars of the cloud complex, to release this energy in a very specific frequency of 656.281 nm.
The Keyhole Nebula
In the center of the Eta Carinae Nebula is the Keyhole Nebula, a small, dark cloud of gas and dust with little arms brighting with fluorescing gas, in a beautiful constrast with the surrounding nebula.
The Eta Carinae 60 MEGAPIXEL mosaic
But I wasn’t happy with the results, for two reasons. First of all, none of both images had enough SNR to bring all details I wanted. And second, this is a huge nebula, and even with my little 66mm f6 refractor, with more than 3×2 degrees of field of view, I couldn’t capture the entire greatness of the Eta Carinae Nebula.
Well, a mosaic and the L-Enhance filter, from Optolong, could fix both issues within one night of imaging.
And so I did.
On May 23, in a full moon, I got some hours of open skies and managed to capture all the light I needed: 4 panels with 1 hour of exposure each.
That seems like little exposure time, but with the Optolong L-Enhance, all those blue light of the full moon didn’t get in the way and I got some nice H-Alpha data.
How to do an astrophotography mosaic?
Well, although it may seems like a challenge, it went easier than I first thought.
First of all, I used N.I.N.A. to simulate the field of view, overlay and every other aspect of the mosaic. At the end, I have noticed that with 4 panels and with a safe 35% overlay betwen each one, I could get the entire Eta Carinae Nebula with some safe space at the sides.
Once all the data was captured, I used Pixinsight, first to substract the calibration frames and than to integrate every one of the panels individualy.
With all 4 panels properly integrated, I did a Photometric Color Calibration in each of then, taking care to properly measure the background level. It really helped a lot later to assemble the mosaic.
And finally I did a Dynamic Background Extraction in each panel to make sure no gradient would interfere on the assemble of the mosaic too.
With the four panels properly integrated, calibrated and everything else, I started using a sequence of the processes StarAlign and GradientMergeMosaic. To asure a good 4 panel mosaic, first I did 2 mosaics, with 2 panels each (2×1), and than I merged these 2 mosaics to end up with a 4 panel (2×2) mosaic.
More or less:
Panel 1 + Panel 2 = Mosaic 1
Panel 3 + Panel 4 = Mosaic 2
Mosaic 1 + Mosaic 2 = Full mosaic
If you want more detail about the process, please, leave a coment here and I will make a full tutorial. And if you don’t have Pixinsight, don’t worry! I’m sure you’ll be able to use Photoshop. 🙂
The final image of the Eta Carinae 60 MEGAPIXEL mosaic
Well, this is the result of 4 hours of exposure and some days of research and editing to get a nice picture:
Sorry for the large wattermark, but recently I had some issues with copyright. I hope you understand. Any questions, just ask. Also, the file have 38,6MB in size. Open carefully.
As I mentioned on the begining of this article, this picture have 60 megapixels. It means I could make a frame with almost 1 meter aside! Nice, hugh?
It also mean that I can make a crop to show you some nice details:
4 panels with 1h of exposure each. For each panel:
- 300s, ISO 1600
- Long Perng S400-G 66/400 F6
- Canon T6i astromod
- iOptron CEM25P
- Optolong L-Enhance Clip filter
- ZWO 60-280 guider
- Photoshop 22.4.1
- Pixinsight 1.8.8-7
Well, I hope you liked it. Maybe I can make more mosaics in the future. 🙂