With the milky way swinging up in the East above 30° around 11:30 pm, I only have three to four hours of narrowband nebula imaging time. Spring is “Galaxy Season” after all, with most of the northern hemisphere night sky time directed away from our own galactic core and into the depths of the known universe. You know, where many of the other galaxies are.

The skies weren’t particularly clear last night, but good enough for some long exposure hydrogen-alpha imaging of the Pelican Nebula (IC 5070) in the constellation Cygnus. The Pelican is the next-door neighbor of NGC 7000, the North America Nebula. With an 800mm focal length and the ZWO ASI1600MM camera I can fit most of the nebula into the frame, a nice clear view of the star-forming structures on the north-facing side, the “top” of the nebula. 

Notes: when you’re shooting five-minute subs, the chances of something happening during any particular exposure go way up--satellite passing through, gust of wind, unanticipated guide corrections from poor seeing, clouds, and other events that affect the image. I shot 49 subs last night and this morning, before stacking, I went meticulously through each and threw out any that had elongated stars, contrast loss (probably clouds), and other artifacts captured during the run. I ended up stacking 38 frames with dark and bias calibration frames (no flats). But that's 38 good frames. Weather: seeing and transparency were poor, and really affected guiding, but still worth spending the time to capture enough data to process. The result is fine. I suspect, the results would be worse with OIII data--OIII being in the middle of the visible part of the spectrum and is probably more susceptible to light pollution, reflection off clouds, ambient temperature changes.

The Pelican Nebula in Cygnus (IC 5070), 3nm Ha filter, 38 x 300-second exposures stacked in DSS, shot with a ZWO ASI1600MM-Pro monochrome camera running at -10C. IC 5070 is part of the larger North America nebula region, about 2600 lighyears away.

May 26 update: IC 5070 in Cygnus in HOO narrowband (Hydrogen-alpha and Oxygen 3 mapped to RGB, with OIII taking both Green and Blue channels). Here's the info on the data I captured: 38 x 300-second Ha 3nm frames, 48 x 300-second OIII 3nm frames with the ZWO ASI1600MM-Pro monochrome camera, cooled to -10C. A little over 7 total hours of data gathering for this one.

Posted May 24, 2023

The “Propeller Nebula” in Cygnus (DWB 118). Imaging notes: 46 x 300-second exposures, 3nm Ha filter, ZWO ASI1600MM-Pro monochrome camera cooled to -10C, 800mm f/4 Newtonian scope, Sky-Watcher EQ6-R Pro mount, William Optics 32mm/120mm FL guide scope + ZWO ASI290MM-Mini guide camera. 

DWB 118 isn't usually called out separately from the vast nebula complex around Sadr, but 193 distinct HII regions are catalogued in the 1969 Ha survey of the Cygnus X Region. The “Propeller” is catalogued as number 118 by the authors, Dickel, Wendker, Bieritz (DWB)

Dickel, H. R., Wendker, H., & Bieritz, J. H. (1969). The Cygnus X region. V. catalogue and distances of optically visible H II regions. Astron. & Astrophys., 1, 270–280. https://articles.adsabs.harvard.edu/pdf/1969A%26A.....1..270D

DWB 118 and surrounding area in HOO. Bi-color processing notes: you may already know that I am a fan of subtlety when it comes to color saturation, even "muted" can be used appropriately in this case. In targets like the Propeller, I think the color serves the dust. If vibrant colors are going to get in the way of showing which structures are in front or behind the dark bands of dust, then I will gladly sacrifice some color.

Posted May 23, 2023

On May 19th, 2023--three days ago, Japanese astronomer Koichi Itagaki discovered a supernova in M101 galaxy, 21 million lightyears away. I shot M101 last week, and tonight I took one exposure in Hydrogen-alpha (narrowband) and overlaid the images. That bright dot circled on the right is SN 2023ixf, the new supernova.

Posted May 22, 2023

Another night out with the Optolong l-eXtreme dual narrowband filter, and again, I'm really surprised at the color and detail captured with the two 7nm band passes, one around 504nm for OIII and the second at 656nm for hydrogen-alpha. Star colors look pretty good, and overall this is closer to true color (red and blue generally where they're supposed to be) than hubble palette SHO images. I captured 55 subs at 300 seconds (5 minutes) each, but threw out all but 28 for processing--it was really windy last night and that just throws chaos into tracking and guiding. I have been doing narrowband imaging with monochrome cameras and separate filters for each bandpass for almost a decade, and that's still my preferred method for capturing deep sky objects like the Crescent, but it's also really promising what you can capture with a cooled color camera in one imaging session.

Cropped to NGC 6888:

Posted May 18, 2023

From my Sunday night astro imaging run: the Pinwheel Galaxy (M101, NGC 5457) is 21 million lightyears away in the constellation Ursa Major. It's quite a bit bigger than our own galaxy: a 170,000 lightyear diameter and a trillion stars. We're looking 21 million years back in time on this beautiful galaxy, tilted perfectly, face-on (or top-down?) from our perspective in the Milky Way, so that we can clearly see its spiral form, twisting dust lanes, HII regions, and other detailed structures. Space is big. And it takes that long for the light of a trillion suns to reach us from this distant galaxy. Imaging notes: about 6 hours of data, 70 x 300-second exposures with the ZWO ASI071 color camera cooled to -10C, UV/IR Cut filter, 800mm f/4 newtonian scope. With a 28.8 arc-minute apparent size, M101 is about the limit for deep sky targets with the 800mm focal length scope.

And here's the full image of M101, the Pinwheel Galaxy, slightly cropped to remove dithering artifacts at the top and side. What's crazy is there are at least a dozen other galaxies in this frame, most of them many more millions of lightyears distant than M101. All of the actual stars in this frame are within our own galaxy, the Milky Way. Everything else is another galaxy millions of lightyears away.

Posted May 15, 2023

I bought the Optolong L-eXtreme dual narrowband filter last year, but I haven't seriously used it until last night. Paired with the ZWO ASI071 and the 800mm f/4 Newtonian, I am pleasantly surprised with the data and processed image. The North America Nebula (NGC 7000) in the constellation Cygnus hit 30° above the horizon around midnight, and I spent over 3.5 hours capturing data, 45 x 300-second exposures stacked in DSS. This has to be the most efficient way to get to a bi-color narrowband image, using a single filter and color astronomy camera. These colors are also close to true in terms of where they are on the visible spectrum, with hydrogen-alpha in red and oxygen III in blue.

Posted May 14, 2023

The M5 globular cluster in the constellation Serpens (NGC 5904) might be the oldest globular cluster in our galaxy, somewhere around 13 billion years old, with the Milky Way itself almost as old as the universe at 13.61 billion years, forming just a few hundred million years after the Big Bang. M5 is about 27,000 lightyears away in the galactic halo, and is one of the largest clusters, with a diameter of about 165 lightyears. Imaging notes: 60 x 60-second subs with the ZWO ASI071MC cooled to -10C and the 800mm FL newtonian scope. 

Take a closer look at the variable double star, 5 Serpentis, lower right with the diffraction spikes (the spikes are an artifact of some reflector telescopes, like the Hubble Space Telescope). If you look closely, you can see both stars, 5 Serpentis A is the larger of the two, with 5 Serpentis B just visible at the lower left of the main star. The main star (5 Serpentis A) is a large F-type main-sequence star, that has been fusing hydrogen like mad, has used most of it up, and is headed toward a red giant phase. Its companion, 5 Serpentis B, much smaller, has recently been estimated to have an orbital period of 3,371 years. 

Posted May 11, 2023

An 8 second exposure of my astro setup during last night's imaging run, shot in the backyard with the Sony A7s and Zeiss Batis 25mm f/2 lens. The skies weren't very clear, with patchy clouds sliding by and overall poor seeing (astronomical seeing represents the impact of atmospheric turbulence), but still managed to capture Messier 5 in the constellation Serpens.

Posted May 10, 2023