31 December 2024
In case you didn’t know, I not only do word origins and historical linguistics, I’m also an amateur astrophotographer; that is, I take pictures of the night sky. I’ve been doing it, off and on, since 2008. This is a compilation of the images I’ve taken during the past year. All but one of this year’s images were taken from my driveway in Princeton, New Jersey, under Bortle 6 (bright suburban) skies.
I post my images to the Astrophotography section of the Wordorigins website and to Astrobin.com. If you want all the technical details (equipment used, camera settings, etc.), Astrobin is the place to find them, along with images taken by amateur astrophotographers from around the world. Click on the links to go to Astrobin to see the technical details and a higher-resolution version of each image.
Astrophotography is more complicated than simply pointing a camera toward the sky. Deep-sky objects are very faint, usually invisible to the unaided eye in light-polluted skies. To get good images, one must have a mount that counteracts the rotation of the earth, allowing you to keep the target still in the frame over long periods. The final images are the result of stacking many exposures of several minutes each, sometimes taken over multiple nights. Above is a photo of one configuration I use. It’s a 127mm (5-inch) reflector telescope on an equatorial mount with a cooled, monochrome, astrophotography camera and filter wheel.
Due to a cloudy spring, the year got off to a very late start. Here are the phases of the total solar eclipse on 8 April, taken at Jay, New York. Like an idiot, I forgot to pack my tripod, so these were taken handheld with a regular camera (DSLR) and my short telescope used as the lens.
Here is M13, the Hercules Globular Cluster, taken on 20 May. Globular clusters are typically found in a halo around the Milky Way (and other large galaxies). This one is about 22 million light years distant and contains several hundred thousands of stars. The photo is a stack of 241 30-second exposures, totaling two and a half hours.
This one is of IC 1311, an open star cluster in Cygnus with associated nebulosity, taken 24 May. This image is a false-color image made up of 71 three-minute exposures totaling three and half hours total integration time. The camera is monochrome, used with narrowband filters to show the hydrogen-alpha (green), oxygen-III (blue), and sulfur-II (red) ionized gases in the nebula. In addition to showing the chemical composition of nebulae, narrowband filters allow you to take images even when light pollution is bad because they “filter out” all other wavelengths of light from sources like street lights and the moon. The limitation is that narrowband filters only work well with emission nebula, those nebula consisting of these particular ionized gases that emit their own light.
This is M8, the Lagoon Nebula in Sagittarius, taken 28–31 May. The nebula is some 4,100 light years distant. The image, like all of the deep-sky images here, consists of multiple exposures stacked together for a total of nearly 10 hours of exposure time. This is another narrowband image, although the stars are true color, taken with red, green, and blue (RGB) filters. I don’t like the look of stars taken with narrowband filters, so when I can I also take RGB exposures and then use software to swap out the stars.
Here is M57, the Ring Nebula in Lyra, a supernova remnant taken 30–31 May. A so-called “planetary nebula” (it has nothing to do with planets), it does not consist of ionized gases, so it has to be imaged with regular color filters. This image is about two and a half hours of integration time. The nebula is some 2,500 light years distant, and the star went nova some 1,600 years ago.
This is the Witch’s Broom, a portion of the Veil Nebula in Cygnus, taken 7–8 June. The Veil Nebula is another supernova remnant, but it consists of ionized hydrogen-alpha and oxygen-III gases, so I used narrowband filters for the nebula and RGB filters for the stars. The nebula is some 2,400 light years distant, and the supernova occurred some 15,000 years ago.
NGC 6888. the Crescent Nebula in Cygnus, taken 9–12 June. It looks sort of like a brain floating amid hydrogen gas. It is formed by the stellar wind from a Wolf-Rayet star (the bright one near the center) that ionizes the surrounding gas and creates a shock wave. It is some 5,000 light years distant. The photo is another narrowband image, Ha and OIII with RGB stars.
The Cygnus Wall, a portion of the North America Nebula, taken 15–27 June. The nebula is some 2,600 light years distant, and the photo consists of 13 hours, 18 minutes of total integration time.
All the images so far (except those of the solar eclipse) were taken with my big 127-mm refractor, which has a focal length of 600mm, giving it a somewhat narrow field of view. Here is a wider view of the entire North America (NGC 7000) and Pelican (IC 5070) Nebulae in Cygnus, taken 31 July with a smaller telescope, 51mm aperture and 250mm focal length, giving it a wider field of view. The camera used here was a color one. The nebula is mostly red as hydrogen-alpha gas dominates, and that gas emits light in the red portion of the spectrum.
M31, the Andromeda Galaxy, taken 11–12 August. Again, using my short focal-length telescope (Andromeda has an angular size of three degrees, six times the width of the full moon) and a color camera. Since galaxies emit light across the entire spectrum, narrowband filters aren’t all that useful. This image consists of ten hours, 20 minutes of integration time. Andromeda is the other big spiral galaxy in our local group and is some 2.5 million light years distant. (There is a third, but smaller, spiral galaxy in our group, the Triangulum galaxy.) Andromeda is moving toward us and will collide and combine with the Milky Way in some five billion years.
IC 1396, the Elephant’s Trunk Nebula in Cepheus, taken 21–24 August. This one also uses a short focal length but with a monochrome camera and narrowband filters for the nebula and RGB ones for the stars, with just over ten hours of integration time. The nebula is some 2,400 light years distant.
Stepping out of chronological order for a moment, I revisited the Elephant’s Trunk on 9–10 October, this time with a color camera.
LBN 487, the Iris Nebula, taken 2–4 September. This is a reflection nebula in Cepheus, meaning that it doesn’t shine on its own but only reflects the light from nearby stars. It is some 1,300 light years distant. Surrounding the nebula are clouds of dust. Reflection nebulae and dust clouds require broadband (i.e., a color camera or a monochrome one with RGB filters).
NGC 7331, the Deer Lick Group and Stephen’s Quintet of galaxies in Pegasus, taken 12 September. These are visual groupings of galaxies, meaning they are not bound together gravitationally, like our own Local Group is, but only appear to be close together from our perspective. The large spiral galaxy at the center is some 39 million light years distant, while the surrounding smaller ones are around 300 million light years away. In Stephen’s Quintet, one galaxy is about 39 million light years away, and may be gravitationally bound to the large one in the Deer Lick Group, while the others are between 210 and 340 million light years distant. These two galaxy groups really need a longer focal length telescope than I possess to do them justice, hence they are very small in the frame. If you click on the link to Astrobin and then view the full-size image, you may recognize Stephen’s Quintet from the movie It’s a Wonderful Life, in which an older image of the group is used in the scenes where the angels are talking to one another.
Here is a wider view of the entire Veil Nebula complex in Cygnus, taken on 9 October. Back in June I took a close-up of the Witch’s Broom, at the bottom of the frame here. This one used a shorter focal length to get the whole complex, which is a supernova remnant. I also used a color camera with a dual-narrowband filter that only captures light emitted by hydrogen-alpha and oxygen-III atoms. Integration time is just under seven hours.
Comet C/2023 A3 (Tsuchinshan-Atlas) taken on 16 October, showing two of the three “tails.” The big “tail” is made up of dust particles blown off the comet by the solar wind. It’s not a true tail as it is pointing away from the sun in the direction the comet is moving. The smaller one, the so-called “antitail,” is a true tail of dust left in the comet’s wake. The third tail, the ion tail, is not readily visible in this image, probably obscured by the main tail. Comets are a challenging target to process. You need a long integration time to capture the faint tail, but during that period the comet is moving against the background stars. It’s a very different post-processing workflow than with deep sky images. This image is a combination of 179 10- and 30-second exposures, totaling just under an hour total.
NGC 7822 and SH2-170, two nebulae in Cepheus, taken 18–20 October. The big nebula is some 2,900 light years distant. The small, round one is known as the Little Rosette Nebula and is around 6,000 light years distant. Here I used a color camera with the dual-narrowband filter. It’s not as effective as using a monochrome camera, as you’re not using all of the camera’s pixels, but it is easier and allows use of a color camera during periods of the full moon. Integration time was 14 hours, 15 minutes.
My final images of the year were taken on 11–13 November of M42, the Orion Nebula. The nebula is the middle “star” in Orion’s sword and is one of the brightest nebulae in the night sky. It’s the closest large, star-forming region to Earth, some 1,350 light years distant. M42 is one the most popular astrophotography targets, perhaps because its brightness makes it easy to find and frame in the view, but the high contrast between the bright core and faint outer portions makes it a very challenging one to process. One photo here is a narrowband image with almost eight hours of integration time; the other is true color, with only fifty-three minutes.
Photo credits: Dave Wilton, 2024. All are licensable under a Creative Commons Attribution-Noncommercial-Sharealike 4,0 International license.
