The Triffid Nebula contains an emission nebula, a reflection nebula, some dark nebula, an open cluster along with some interesting unusual objects thrown in for good measure.  It lies at a distance of about 4,100 ly and subtends about 28 arc-minutes of arc.  With an apparent magnitude of 6.3, it’s among the most popular objects in the sky for amateur imagers.  Energetic photons from a bright central star, HD 164492A (type O7.5III) with a mass of around 20 solar masses, produces the pink/red emissions from elements, mostly Hydrogen, in the main part of the nebula.  The central star is surrounded by a cluster of approximately 3100 stars.  Blue light from the hot central star reflect to produce the blue clouds surrounding the main emission nebula.

This image reveals a region about 8 ly from the central star where new stars are forming and where a Herbig-Haro jet (HH399) can be seen.  When I first spotted this object, it reminded me of a similar object in the Pelican Nebula so I’ve included an image comparing both.  Herbig-Haro objects are proto-stars associated with long ejection jets illuminated by nearby stars.  The ejection mechanism is not well understood but it is likely driven by strong magnetic fields accelerating and ejecting ionized gases in a collimated, narrow beam along the rotational axis of the object.  HH399 has a length of about 16 arc-seconds, which puts its length at about 0.32 ly.  It has been studied using Hubble data to determine its proper motion to better understand the nature of the jet. If you look just to the right of HH399, you’ll see a finger-like stalk pointing directly at the central star.  That stalk is formed from evaporating gaseous globules (EGGs).  The head of the stalk is dense enough to shadow the material behind, preventing the stalk from being dispersed by the powerful radiation from the star.  You can find an excellent paper about HH399 that appeared in the Astrophysical Journal here:  https://iopscience.iop.org/article/10.1086/428706/pdf.

I’ve been so caught up with other projects for the last couple of months that I’m accumulating a big stack of unprocessed data from the 20”.  I started working on this image back in April when I first spotted the Trifid rising in the sky.  I’ve imaged it a couple of times from Oregon but it’s always been low in the sky and I couldn’t resist the opportunity to give it a try from Chile.  The problem is that by the time I got the scope on it, the weather started to shift toward winter in the S. Hemisphere.  The seeing was generally poor, the wind came up, and although I gathered over 500 subs for the LRGB channels, I had to toss out 2/3 of the data—just to reach a FWHM threshold of 2.2”.  The seeing really laid waste to the resolution possible with a 20" aperture.  So, this image isn't any sharper than I could have gotten with my 14" and heck, it might be rivaled using a C11.  There were also a lot of subs ruined by high-thin clouds.  The clouds manifest as a large glow around all the bright stars—and this is why it’s important to blink through your data before you stack!  I really hated tossing out so much good data but when there’s enough of it, cloud-glow can really screw up an image.  I also gathered about 300 subs in Ha and O3 thinking that I’d doing something “spectacular” with all that data.

Once I struggled through that huge mass of data (~800 subs at 123MB/sub = 0.984 TB), I started messing around to see how I might blend in the Ha data.  I started by computing the raw Ha contribution, thinking that I’d simply add it in proper proportions to the red and blue channels.  But no matter how I cut it, I couldn’t get a pleasing result.  Long story short, I found the same thing with the O3 data.  I just couldn’t combine it in any good way to make the LRGB data look more interesting than it did on its own.  I’ll save all that data and produce a NB image when I get a chance to gather some S2 data.  Oh well.  

The LRGB data looks great on its own.  My biggest regret is that I couldn’t have gathered better data!  So I’ll have to try again in the future.The final challenge for this image was to get the background “right”.  I tend to like dark backgrounds but I realized that in this case, the Trifid lies in sea of dust and reddened stars so I did my best to preserve the background colors and brightness.  It may still be just a bit darker than it should be but to test it, I superimposed it on one of my Hyperstar images of the same region.  The Hyperstar image probably isn’t exactly right but as you can see, this result isn't too far off. 

As always C&C is more than welcome so feel free to let me know what you think.
John