Image 1: Milky Way from the north shoreline of Lac Teeples looking South, July 14, 2023. This version based on combining/stacking a small number of subframes.
Image 2: Milky Way from the north shoreline of Lac Teeples looking South, July 14, 2023. This version based on a screen capture from my imaging software.
The most popular astrophotographs are probably wide-area shots of the Milky Way. The images capture the blotchy light of billions of stars, with some prominent individual stars plus light and dark nebulae scattered across the field. The light forms a line because we are looking along the Milky Way’s thin disk. In the foreground we typically see rocky outcrops, old barns, trees, humans, or some such thing which help put the image in perspective. The wide field means that the photographer must choose his/her location carefully: All of the scene must be quite dark or the image is ruined.
The Milky Way appears as a band that twists across the whole night sky, at an odd angle to the equator and not matching the sun’s path in the sky. The brightest part of our galaxy is the centre where there are more stars. This is best viewed in the southern hemisphere: The galactic centre is near -30 declination, which can’t be viewed from my normal cottage location. I am generally limited to the band of the galaxy north of the galactic centre.
Any astronomical object is best viewed when it is highest in the sky. This is certainly true for shooting from my cottage with the forest blocking the view. Waiting until the target is highest in the sky also means the atmosphere has less (negative) influence on the image. Image 3 shows the path of stars in the sky from a spot in California. Look at the right, the “apparent path of a typical southern star”. That star is highest in the sky when it is due south. Our southern Milky Way follows a similar path – we see more of the bright parts when they are aligned due South. At noon, when our own star is highest in the sky, it is due South.
We want to do our photography looking South when the Milky Way is aligned and is highest in the sky. We also need to do this sensitive work well after sun down and when there is no moon – and when the sky is clear! For me, in Canada in 2023, there was really only one reasonable time window, near the new moon in mid-July. Other times in July have some amount of moonlight. Mid-August may allow a bit of time between the sunset and the target moving too far to the West but it is a narrow window of time. Mid-June is at the Summer Solstice and there are only two or three really dark hours at night. It may have been possible in mid-May before dawn but I am not a morning person…
Image 3: Path of stars in the sky (thanks to U. C. Berkeley)
I’ve explored several areas north of Ottawa (the area of my cottage) and many are too close to the city: The camera is pointed due south right at the city’s light pollution. The further you go north the less developed is the countryside (fewer parks, fewer picturesque foreground barns). An obvious solution is to go south of the city, far enough to leave the city’s light pollution but not so far as to start seeing the light plume of the next town. This exploration will continue.
Nevertheless the resulting images can be well worth the effort.
Image 1 was captured in mid July, a rare clear night nearly at the new moon. My intention was to capture the Milky Way and a reflection of it in the lake. By going to the North shore I could also see further south because I was a good distance away from the trees that block the southern horizon. I knew that there were some light-polluting cottages but I hoped for the best.
In the early evening I bushwacked to the shoreline of Lac Teeples and located a good spot. I flagged this “path”. At 11pm I wandered out with my gear (gardening clippers, chair, tripod, camera, computer, battery pack…) and set up. Of course, I lost the trail almost immediately and bushwacked to a different spot, which was probably a bit better.
Then I realized that the cottage facing me was lit up like Manhattan and another one was similar just to the west (at the end of the lake). To the East I could see several brightly lit cottages. There was a bit of a dark gap between them (incidentally where my cottage is) and I had to wait for the target to move closer to that spot. Even then the light pollution was overpowering everything. There was a bit of mist and the cottage lights were causing a huge glow in the sky above the entire lake - hundreds of meters. Nearly everywhere I looked the sky was a mess. I also had to wait around 30 minutes for the twilight to go away. The mist cleared up for a while but the results were very limited by pollution. By 12:15 it was getting foggier and I packed up and went home. The image shown here was captured around 11:45pm.
What do we see here?
At the very bottom of the image, along the horizon just to the right of a bump in the trees is a star cluster known as Messier 7, Ptolemy’s Cluster. This is at a declination of -35 degrees, far to the south of my normal tree-obscured horizon – 30 degrees better, in fact! The large white patch near the bottom is called the Large Sagittarius Star Cloud. The centre of our galaxy is in the direction of this star cloud, which shows the bulge of stars near the galactic centre. Above the star cloud is a fairly big red blotch. This is the Lagoon Nebula. The tiny red nebula just above it and a bit to the right is the Trifid Nebula.
Working our way up we see a large foreground tree branch cut across the scene diagonally. Just above this and moving a bit to the left we see another star cloud. This is, you guessed it, the Small Sagittarius Star Cloud, or Messier 24. To the left of this cloud is a small star cluster, known as Messier 25 or the U Sagittarii cluster. A similar distance to the right is another cluster, Messier 23 (visible in Figure 1 but blocked by the foreground branch in Figure 2). Above the smaller (and brighter) star cloud we see two more red nebulae. The lower one is the Omega or Swan nebula. The next one, slightly larger, is the Eagle nebula, home of the famous "Pillars of Creation".
The star mid way up on the far right is SABIK. The star roughly in the centre of the image, just below the foreground tree branch is ALNAM. The image shows parts of the constellations Sagittarius, Scutum, Scorpius, and Ophiuchus.
Figure 1 is the blending of several images over a period of around 5 to 10 minutes (only). The camera was tracking the stars, so the foreground will move relative to the fixed stars and the result is that the foreground tree branches are blurry. Figure 2 is a single image of 30 seconds and as a result the movement of the trees relative to the stars is much less. The tree branches in Figure 2 are much sharper.
These images of the Milky Way were captured with a ZWO ASI-294MC Pro camera, a Canon EFS 24mm pancake lens, an Astromechanics focus controller and a Sky-Watcher Star Adventurer mini mount on a tripod. A ZWO duo-band filter was used to enhance the red nebulae. The tripod was jammed into the mud at the side of the lake. All these photography materials are very easily carried in a small bag.
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