Constellation Crux and Coalsack Nebula (C99) (Re-Work)

In April 2021 I posted here a new version of a capture made in July, 2020. Well, I was not entirely happy.

Then, I decided to do a new version. This means that the picture I’m posting today is at least the 3rd version of the same data. Ok, ok, sorry. I won’t be stalling. Here is the new (And hopefully the last) version:

Crux and Coalsack Nebula (C99)

Also, I made an annotated version, with the astrometric solution. What are your thoughts?

Crux and Coalsack Nebula (C99) with astrometric solution
Crux and Coalsack Nebula (C99) with astrometric solution


This is the equipment I used to capture this image:

No autoguiding this time!

And the lights:

  • 142x30s (Total of 1.2h of exposure);
  • ISO 1600;
  • Bortle 6 skies;
  • Moon: 81% illuminated;
  • No darks, flats or BIAS;
  • Data captured on July 9, 2020;

Eta Carinae Nebula in a 60 MEGAPIXELS mosaic

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

The Keyhole Nebula and the Eta Carinae Star
The Keyhole Nebula and the Eta Carinae Star

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

As I mentioned before, I already have a picture of this DSO. To be honest, I have at least two images, one with my old D5000 and one with my new Canon T6i.

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.

The Optolong L-Enhance Filter

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
And than:
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 main source of my learning process is the Amy Astro’s Youtube Channel. Her channel is awesome! And she also have a pretty nice website.

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:

Eta Carinae Nebula in a 60 MEGAPIXELS mosaic
Eta Carinae Nebula in a 60 MEGAPIXELS mosaic

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:

Some inner details in NGC 3372
Some inner details in NGC 3372
NGC 3324 - The Gabriela Mistral Nebula
NGC 3324 – The Gabriela Mistral Nebula


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

For autoguiding:

  • QHY5L-ii
  • ZWO 60-280 guider
  • PHD2

For editing:

  • Photoshop 22.4.1
  • Pixinsight 1.8.8-7

Well, I hope you liked it. Maybe I can make more mosaics in the future. 🙂


Constellation Crux and Coalsack Nebula (C99)

This image of the Constellation Crux and the Coalsack Nebula (C99) uses one of the first light captured with my Canon T6i, back in July, 2020, with a 135mm lens. I just totally forgot to proccess this one! Shame on me.

These are two objects really close on to each other on the southern hemisphere. And although they’re very close to each other, they’re also very different. Let’s talk about them?

The Crux constellation

The constellation Crux is one of the easyests constellations we can identify on the southern hemisphere. In a shape of a crux (You don’t say??), it is located inside the constellation Centaurus and next to constellation Carina.

The alfa of the constellation Crux is also knowed as Acrux or “The Magellanic Star”. It is very bright and easy to identify. Through a telescope, though, Acrux shows itself as a incredible double star.

On the left arm of constellation crux is located the Jewel Box, a very beautiful open cluster, visible with naked eyes but gorgeous through a telescope or a binoculars.

The Coalsack Nebula (C99)

The Coalsack Nebula, or Caldwell 99, is the biggest dark nebula of the entire sky. On a dark sky location, is visible through naked eyes, obscuring the milky way stars next to the constellation Crux.

When I say that it’s the biggest dark nebula, is because it is big. Really big. Even through my 135mm lens I can’t get it’s full extension. And it’s so big as it’s beautiful.

My first capture with the Canon T6i

When I bought my Canon T6i (Canon 750D), the skies cleared up for 1 or 2 days, and I managed to capture about 1h of the constellation Crux and Coalsack Nebula. But, for some sort of a reason, I totally forgot to proccess those lights captured.

Some time later, with clouds on the sky for months, the abstinence made me search for some light frames to process, and bang! I found 142 frames of 30 seconds with my Nikon 135mm f2.8 Ai.

After some time processing it, here is the result:

Constellation Crux and Coalsack Nebula (C99) at 135mm
Constellation Crux and Coalsack Nebula (C99) at 135mm

What are your thoughts?


This is the equipment I used to capture this image:

No autoguiding this time!

And the lights:

  • 142x30s (Total of 1.2h of exposure);
  • ISO 1600;
  • Bortle 6 skies;
  • Moon: 81% illuminated;
  • No darks, flats or BIAS;
  • Data captured on July 9, 2020;

Messier 42, The Orion Nebula – a new version

On November 2020 the skies allowed me to shoot Messier 42, The Orion Nebula, again. This time I used my new camera and light pollution filter, and now the result is… kinda ok.

I got only 55 minutes with 30s frames, but the surrounding nebulosity already begun to show itself.

My new field flattener also helped a lot to flatten the borders of the frame!

Messier 42 does not require any comments. It’s probably the most known nebula of the sky, visible through naked eyes!

The Orion constallation is full of this emission nebulas, but M42 is by far the most proeminent.

Enough talking! Here comes the pic:

Setup for photographing Messier 42

Canon T6i (750D) astro modified
Long Perng S400M-C 66mm f/6 refractor
Field Flattener for short refractors (Looks like Orion Field Flattener)
iOptron CEM25P with a 2″ tripod
ZWO 60280 Finder and Guide Scope
QHY5L-ii Color


110 x 30s
ISO 1600

See in more detail:


NGC 5139 – Omega Centauri

NGC 5139 – Omega Centauri, the largest globular cluster of the night sky, but only visible from the southern hemisphere. Would it be a good target to test new gear?

My new gear

In July I bough a Canon T6i and a field flattener for my Long Perng S400M-C 66mm f/6 refractor . I was so excited with my new gear that I took some pictures, did a basic processing and then totally forgot to publish it.

The gear I shooted NGC 5139 - Omega Centauri: New Canon T6i and Field Flattener
The gear I shooted NGC 5139 – Omega Centauri: New Canon T6i and Field Flattener

I choose this one as my first test by two reasons. First one, I have already taken a picture of this globular cluster with my old Nikon D5000, and it would be a good comparison.

Second, this is an easy target, but this field full of stars is a good way to measure focus and focal plane correction. Besides, there are some faint galaxies around NGC 5139 that only a good exposure could solve.

The differences are huge. My Nikon D5000 have 12.3mp, and my new Canon T6i have 24mp. Twice the number of pixels. This mean that now I’m closer from the correct arcsec/pixel ratio for my telescope, but also means that my computer strugles a lot more to pre/pos process the images.

At the same time, now I can use almost all the field of view of the image, thanks to the field flattener.

The night didn’t help

I wanted to make at least 4 hours, with frames of 180 seconds. But I knew the clouds would came fast. Then I stayed with 60s frames.

My bortle 6 skies don’t wan’t to help, and my optolong L-Pro still didn’t arrived.

The results: NGC 5139 – Omega Centauri

Oh my, I love this giant!

NGC 5139 - Omega Centauri



  • 88x60s
  • ISO 1600
  • DARKS: 100
  • FLAT: 50
  • BIAS: 150

Cat’s Paw nebula – NGC 6334

NGC 6334, the Cat’s Paw nebula is a faint emission nebula on the constellation of Scorpio.

That’s finally my last capture before I get my DSLR modified for astrophotography.

My setup for astrophotography is slowly getting the way I want!

Of course, my ideia was to shot an emission nebula hard to capture with a stock camera. If everything ends right, soon I’ll post a version of this same target, with some quite similar exposure, but with an astromoded Canon T6i. Wish me luck!

Well… the Cat’s Paw nebula is a hard target for Bortle 6 skies and a stock DSLR. Almost 3 hours of exposure and I hardly got some nebulosity. I hope it will change soon, as soon my camera come back and my Optolong L-Pro arrive.

Here it is:

Cat's Paw Nebula - NGC 6334
Cat’s Paw Nebula – NGC 6334



  • 87 x 120S
  • ISO 1600

My sky is getting worse

Well, when I was using my Nikon D5000, the light pollution was a problem, of course, but not a major one. I mean, I was using ISO 400, and 120s frames apear not too gray at the time.

As soon I as put my hands on my new Canon T6i, I saw the real problem. 120s subs with 1600 ISO are enough to let the frame almost white!

Look at this:

120s ISO 1600 SUB -  Cat's Paw Nebula - NGC 6334

This is one single frame with 120s of exposure time and 1600 ISO.

Optolong L-Pro Clip Filter on the way

To fix (or at least try) this issue, I bought a Optolong L-Pro Clip Filter. I’m in Brazil, and it’s coming from China, so… just imagine how long I’ll need to wait…

But don’t worry!

Canon T6i astromod on the way

Also, I just sent my new Canon T6i to be modified for astrophotography.

As you can imagine, I can’t even sleep.

As soon as I put my hands on the canon again I’ll try to shot the Cat’s Paw once more!

See you soon!


Crux and Coalsack Nebula (C99)

The Crux constellation and the Coalsack Nebula (C99) are so close to each other that we can shot it through a 135mm and a cropped APS-C sensor.

And I finally did it! Let’s see how it ended.

The Crux constellation

The Crux constellation is probably the most known constellation of the southern hemisphere, and it’s easy to understand why. There are 4 stars, being the less brighter yet on magnitude 2.75, and disposed on a “cross” shape very easy to locate.

This constellation is full of surprises. Just to the left of the star called “Mimosa” (Beta Crucis) is the Jewel Box (NGC 4755), a beautiful, bright open cluster with stars of many colors.

The star Alfa Crucis, also known as “Magellanic Star”, is the brightest one, with 0,8 mag. This is also a multiple stelar system, with at least 3 stars.

The Coalsack Nebula (C99)

I don’t know why, but I just love dark nebulas. And the Coalsack is awesome! C99 is the biggest one seeing from earth, with dimensions of 7×5 degrees! It is HUGE!

I first discovered C99 a few years back, while I was on the firsts steps with astrophotography. I pointed my D5000 to the Crux with a tripod and toke some 15s shots. When I saw this huge shadow I couldn’t believe.

The picture itself

Shot it was pretty easy, to be fair. I started just after the sunset, but the first 4 frames was lost due to the INTENSE traffic of artificial sattelites. I should have thinking on that, right?

Then I made more 96 frames of 60 seconds with my D5000 and my Nikon 135mm f2.8 at f4.

This was the result:

Crux and Coalsack Nebula (C99)


Nikon D5000
Nikon 135mm f2.8 AIs at f4
iOptron CEM25P


96 x 60s ISO 400