The Rho Ophiuchi cloud complex is a dark nebula of gas and dust located just south of the star ρ Ophiuchi of the constellation Ophiuchus. At an estimated distance of 130-ish parsecs (about 430 light years) this nursery is one of the closest star-forming regions to our solar system. It is also one of the most colorful areas of the sky because the nebulae surrounding Rho Ophiuchi display a wide range of cloud phenomena. Rho Ophiuchi, a bright triple star, is surrounded by the blue reflection nebula, IC 4604. The blue star Sigma Scorpii is surrounded by an intense red hydrogen emission nebula. Adjacent to Sigma Scorpii is the large globular cluster M4. Despite its apparent association with the surrounding nebulae, M4 is actually a much more distant background object at about 7200 light years away. A second globular cluster hidden in the nebulosity around the red supergiant, Antares (meaning “rival of Mars”), NGC 6144, is also a background object at 33,000 light years away. Antares is so large that, if it were at the center of our solar system, its outer atmosphere would reach to the orbit of Jupiter. Antares strong stellar wind has created the relatively cool yellow nebula, IC 4606, that seems to engulf the star and obscures NGC 6144. The blue reflection nebula, IC 4605, next to IC 4606 is reflecting the blue light from the star it surrounds. Part of the the dark nebula, B44 (commonly known as “The Dark River”), is seen spilling through the complex. This nebula is created from dust that is in front of the surrounding nebula and causes us to see it in silhouette.
I ran into a lot of issues this weekend trying to get some new (to me) tech working correctly. I am trying to transition from a SynScan hand controller on my equitorial mount to an EQ direct ASCOM interface so I can slew to targets from within TSX. I have the basics working (like COM port access and EQ-MOD control of the mount), but I’m having trouble with alignment and accurate pointing. I tried feeding 15 star alignment points into the T-Point plugin, which took a couple of hours, and was unable to resolve accuracy problems. I ended up switching back to the old way to try and salvage some night sky. It was cold and I was tired, so I just imaged Messier 101 (The Pinwheel Galaxy) with no filters. The dwarf galaxy NGC 5474 is also prominent in this grayscale image as well as NGC 5477 and NGC 5457. There’s nothing like a night out imaging after a long hiatus to remind you the important role proficiency plays in consistent results.
I have a long way to go when it comes to PixelMath. Thankfully, helpful folks like David Ault (Cloudy Nights) have provided some great examples for me to reverse engineer and try to understand. Here is my second attempt at processing the original Rosette subs into something similar to a bicolor SHO palette. This was accomplished by generating a synthetic green channel with the following PixelMath:
Arg… it’s been a long time since I attempted to image, but Dave and I made it out last night for a few hours. We discussed attempting the Rosette Nebula since neither of us had ever tried to image that target before. It seemed to be up for a reasonable window and bright enough for us to get some data from the yellow-ish/green zone at Tranquility Base. Dave continues to have camera control issues from his computer and I feel bad that I can’t be of more help due to my ignorance around the Nikon platform. He ended up shooting M81 and M82 unguided using a handheld intervalometer (off-body shutter trigger with an interval timer built in) and it worked quite well. I started out shooting with a hydrogen-alpha filter because the moon was quite bright. I think we are less than a week from it being full at this point. I didn’t think I’d have enough time to get sufficient RGB subs, so I had to make the call to either hoard a bunch more Ha data the rest of the imaging window or attempt a bi-color rendition of the target. I’m pretty new to narrowband integration and haven’t done much of anything using synthetic palettes other than perhaps the North American wide-field last year, so I switched to shooting Oxygen III until the nebula was obscured by Loblolly pine tree tops. I lost a handful of subs due to clouds and another handful of subs due to silly mistakes that I blame on a quarter year hiatus… like not meridian flipping before tracking fell off a cliff. At any rate, this image represents 46 sub-frames at 300s each (28 Ha and 18 OIII). I used a previous master suber-bias and master dark that I had in the library. I don’t know if the master dark temperature compensation was the same, but whatever (FWIW, this was shot at -5C). I wanted to process this in SHO Hubble Palette, but honestly couldn’t remember how to do it, so I just went with a natural synthetic green channel using a 10/90 PixelMath blend of the Ha and OIII channels. The original Ha stack had far better signal to noise due to the greater number of subs and stronger Ha emission, so I used it for the Luminance rather than extracting Lum from the blended RGB. All of the registration, calibration, and integration was done in PI and then I just used PS CC for re-sizing for the web. This turned out to be a lot more interesting target than I anticipated and would really love to spend some time accumulating more (deeper) frames and try different processing techniques. Cheers!
I wanted to share just the Ha data because out of everything I attempted this weekend, the integration of the Ha data was my favorite result. I love the dust lanes that show up in space with the deeper exposures. I love the gradients in the emission nebula. I love the contrasts in this image and could see trying this again. I didn’t do much here other than register and stack the Ha subs, did a quick dynamic crop and ABE, convert to non-linear, and resize for the web. I think this is only about an hour of Ha. It makes me want to pull down several nights of light and print up a wall hanger!
There is a section of space in the Orion Molecular Cloud Complex called Barnard’s Loop (Sh 2-276) that contains the dark Horsehead and bright Orion nebulae. This image is more or less the “center” of the loop. The stars within the Orion Nebula (on the right) are believed to be responsible for ionizing the loop as is Alnitak aside the Flame nebula on the left. Alnilam and Mintaka are also seen in Orion’s belt on the left. All this stuff is several hundred parsecs away and some of the coolest and well known of DSOs in the night sky. I tried to do something experimental (for me) here by replacing the Red channel with Hydrogen Alpha in a standard RGB integration. That’s is at least part of why it looks so bloody (because when Hydrogen electrons fall to their lowest energy level… like in an emission nebula… they release photons at 656.28 nm… which is quite red to our seeingballs). It turned out a little more cartoony than I’d imagined. I bet it could be toned down to look a lot better, but I just went with the first pass at it because I realized I just didn’t have enough green or blue channel data to pull this off. The Ha data was a lot deeper too… 10 minute subs versus 5 for the G and B.
We had a little time between Cygnus setting and Orion rising above the tall pines around us, so I just grabbed some Andromeda while waiting.
Dave and I headed out to Grimes county Saturday night for some practice. I wanted to try and image the entire Veil, so I took the 70-200mm lens again. Setting up went fairly smooth, but I had some issues with focus. I could never get below a FWHM of about 5 in the focus tool and I’m not sure if it was me, the wider view, the lens and associated focus ring, or what… but I went with the best I could manage. My stars always seem bloated or fuzzy and again, I don’t know if it’s me or my set-up. I did notice in processing that I clearly need to learn the toolset better in PixInsight (deconvolution, morphological transformation, TGVDenoise, ANCDR, ATrousWaveletTransform, etc). It felt great to have a nice and clear night out and to get some practice under my belt.
“The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop, a large but relatively faint supernova remnant. The distance to the nebula is not precisely known, but Far Ultraviolet Spectroscopic Explorer (FUSE) data supports a distance of about 1,470 light-years. In modern usage, the names Veil Nebula, Cirrus Nebula, and Filamentary Nebula generally refer to all the visible structure of the remnant, or even to the entire loop itself. The structure is so large that several NGC numbers were assigned to various arcs of the nebula. There are three main visual components:
– The Western Veil (also known as Caldwell 34), consisting of NGC 6960 (the “Witch’s Broom”, “Finger of God”, or “Filamentary Nebula”) near the foreground star 52 Cygni;
– The Eastern Veil (also known as Caldwell 33), whose brightest area is NGC 6992, trailing off farther south into NGC 6995 and IC 1340; and
– Pickering’s Triangle (or Pickering’s Triangular Wisp), brightest at the north central edge of the loop, but visible in photographs continuing toward the central area of the loop. NGC 6974 and NGC 6979 are luminous knots in a fainter patch of nebulosity on the northern rim between NGC 6992 and Pickering’s Triangle.
The nebula was discovered on 1784 September 5 by William Herschel.”
Although probably not the most mature decision, I couldn’t let the serendipitous alignment of crystal clear skies, cool weather, a new moon, and a weekend pass without maximizing the exploitation of said gooderies. I drove back to Huntsville last night and imaged the Cygnus region again. Specifically, it was NGC 7000, the North American Nebula and it was all wide-field. I had this grand plan to reconfigure the CCD with a directly attached plate to mount it with my fastest lens, the EF 85mm f/1.2L, and bin the narrowband exposures for some crazy signal to noise ratios. However, I had conveniently forgotten that the 85L focuser required power and could not be manually focused. Fortunately, I brought a back-up lens and albeit less sharp, the EF 70-200mm f/2.8L IS on the wide end was close to my desired field of view. I started out with a 2×2 binned Hydrogen Alpha, Sulfur II, and Oxygen III run and switched to a non-binned Luminance run after the meridian transit without consideration for the added difficulty of integration or the lack of need for Lum data when integrating NB. This is how we learn. Anyhoo, I didn’t get home until 6am and only got a couple of hours of sleep before I needed to be up and functional. It took some doing, but I managed to pull together a “first pass” at this data. I need to digest a little tribal knowledge before making another attempt. This is a lot more complex than I anticipated.