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.
I’m on the fence about heading back out tonight for some wide-field imaging. I have this idea about going deep RGB on NGC7000, but not shooting full spectrum red at all. Shoot Ha for the red channel and standard green/blue all binned 2×2 and then shoot a luminance set binned 1×1 and see how that turns out. I think I could pull it off in one night because of the lens speed, but it’s a big effort to pack up and drive an hour+ each way a second night in a row.
Disappointed that I didn’t capture what I set out to last night, I was cold and done with time to wait while another imager was finishing his run of 15 minute subs, so I set up a short series of 5 minute luminance subs while we waited for our window to tear down. I registered those this morning and manually integrated them, then took an already integrated OSC data set from October of 2014 that I shot with a stock DSLR and converted both from linear to non-linear and did a simple LRGB combination folding the new lum data into the old color data. I didn’t do a color calibration or anything, so I’m certain there are far better ways to do this… I was just messing around and didn’t want to waste the data. It didn’t turn out half bad! Once I develop my post-processing Fu some more, I would like to have a catalog of “good” data that I can keep adding to over time.
It was a beautiful night last night. The sky was clear and dark (moon at 2%). Due to some power problems at Tranquility Base, Dave and I had to divert to the observatory in Huntsville. By the time we arrived, it was dark, so it was good to practice assembling my entire imaging rig almost entirely by touch. I had a little issue with balance due to using my older side-by-side saddle because I wanted the faster f/4 focal ratio of my camera lens versus my f/7 refracting telescope. The configuration is a little wonky and whether it works well or not depends greatly on where the target is in the sky relative to the meridian. This also impacts my star alignment routine because in order to get the parallel imaging element and guide element pointed the right way using the saddle, I have to rotate the equatorial mount head 90 degrees on the declination axis. I can’t prove this should cause an issue, but it seems to always give me trouble – so maybe it’s just me. The result is longer/multiple alignment passes and often missing targets on the slew stop. This happened last night. I was trying to locate NGC 6888 for my first bi-color narrow-band attempt. Cygnus was high in the sky and I felt really excited about having a solid imaging run ahead. The only problem was – I never found the target. After several hours of tinkering, I decided to just image where I was at and try another night for the Crescent. It wasn’t until I plate solved the result that I found I was somewhere very near IC 1318, the diffuse emission nebula surrounding Sadr (or Gamma Cygni). I was close, but the temperature was quite surprisingly dropping and I wanted at least something to practice with in post. I love being barefoot. Somehow I must have subliminally “forgotten” my shoes when I left the house and I also just-so-happened to be in my usual uniform of shorts and tee-shirt. When the temp bottomed out at 59 Fahrenheit, it was time to pack up and head home.
I went back out to the SHSU Observatory last night to take advantage of the clear skies and absence of moon. Instead of the EON 130mm APO, I decided to test out the SBIG Canon EF adapter on the STF-8300M and see how it worked out. I hadn’t balanced and shot with the side-by-side saddle in a long time, so there was some risk in making my already marginal tracking worse with a balance issue, but I was hoping the faster f/4 aperture of my EF 600mm f/4L IS lens would improve the amount of signal I could pack into a short night out. With AP, nothing goes exactly as you planned most of the time… and last night didn’t disappoint. The mystery fuzzy/focus/dew problem came back even though I had used the heat of the entire day to ensure I was synchronized with the ambient temperature. I tried modifying the set point cooling (again) thinking that might help, but it didn’t do much. Then, I had a eureka moment. I noticed that if I spun the FW8-8300 to the empty slot, I could image a relatively crisp starfield… but if I took sample shots on any other filter setting (R, G, B, LP, Ha, OIII, SII), I was in the fuzzies. It was the filters that were dewing out! (or so it seemed)… gah! Now what? Fortunately, Dave was there and had an extra long velcro dew strip that I wrapped around the protruding section of the FW8-8300 and cranked up on the max setting. After some time, that seemed to help. It will take another night of imaging to really test if this is “the fix” for dealing with the extreme Texas summer humidity. By the time I troubleshot and quasi-corrected the issue, it was after 11 and I’d lost a good chunk of my short night. Another silly mistake where I had not noticed a deselection of auto-save subs in TheSkyX caused me to lost about half an hour of great blue channel subs that I had to re-do. All said, I ended up staying later than I should have and didn’t get home, unpacked, showered, and in bed until 6:15. Sleep fast!
I really need some more practice. I am introducing a lot of noise in my workflow somewhere… or maybe it’s just in my data. I seem to lose star field color when I try to integrate Ha into the LaRGB. I get way desaturated combinations when combining luminance into RGB using only the Lum channel and weighting it and colors that are way over saturated if I use chrominance noise reduction in that step. I just used the LRGB tool here and skipped several steps of my old workflow because I am just not getting it. Maybe I need to sleep on it and come back with a fresh start.