Composite image showing the orbital movement of Sirius B spanning a 9 year period, from 2012 to 2021. | Astrophotography | SkyNews
Sirius B orbiting Sirius A, by André Montambault

Orbit of Sirius B by André Montambault

The Photo of the Week winner on April 9, 2021 is a composite image showing the orbital movement of Sirius B over nine years by André Montambault.

The Photo of the Week winner on April 9, 2021 submitted something a little different — a composite image showing the orbital movement of Sirius B spanning a nine-year period, from 2012 to 2021, by André Montambault.

Composite image showing the orbital movement of Sirius B spanning a 9 year period, from 2012 to 2021. | Astrophotography | SkyNews
Sirius B orbiting Sirius A, by André Montambault
Composite image showing the orbital movement of Sirius B spanning a 9 year period, from 2012 to 2021 (with labels). | Astrophotography | SkyNews
Sirius B orbiting Sirius A (with labels), by André Montambault

Located about 8.6 light-years away in Canis Majoris, Sirius is the brightest star in the night sky at magnitude −1.46. Sirius A is a main-sequence star with about twice the mass of our Sun. Astronomers estimate that its companion star Sirius B — discovered in 1862 and the closest white dwarf to us — is smaller than the Earth but has a mass equal to about 98 per cent of our Sun. Sirius B’s orbit around Sirius A is estimated to be about 50 years.

During the last decade, Montambault said he completed three photographic detections of Sirius B:  the first was on March 19, 2012; the second was on February 22, 2016; and the third was March 9, 2021.

“Our 45-degree north latitude makes this an even more interesting challenge,” he wrote.

After posting the image from March 9, 2021, Montambault — who lives in Drummondville, Québec, and shot from his backyard — said it occurred to him that maybe the three images together could trace a part of Sirius B’s orbit.

“I had certainly not planned for the eventuality, but maybe it could work, notwithstanding the limited precision of an amateur’s equipment,” he wrote. “The setups for 2016 and 2021 were nearly identical. The setup for 2012 was very different.”

Montambault said that in 2012 he used an f/10 SC8 telescope in altitude-azimuth mode, with a Neximage camera (with “long-exposure mod” to exceed the inherent exposure limit of 1/5 sec), a 3× Barlow lens (therefore yielding f/30), and capture software K3CCDTools. He captured 1,000 0.5-second exposures. The resulting overexposed image of Sirius was a brilliant round object.

In 2016 and 2021, Montambault used an f/10 SC11 telescope in equatorial mode, with a ZWO ASI120MM-S camera, a 3× Barlow lens, an hexagonal mask and the capture software SharpCap.

“About 850 frames were captured in this setup, in five minutes, at 350 milliseconds exposure time,” he wrote. “The resulting overexposed image of Sirius had six marked spikes, aiding in the detection of B when the mask and spikes were properly positioned. Though I had no mention of such in my logbooks, there could have been some minor differences in the setups of the two years and this could introduce some error.”

He made special note of the Trapezium Cluster in Orion, which he also imaged in all three photo sessions using the same setup as he did for his Sirius images.

“The basic reason was to have a photographic yardstick by which to judge the separation of A and B in my images, given that the distances between the Trapezium stars cover a similar range (i.e. from about 8 to 13 arcseconds),” he wrote. “Also, as it turned out, the Trapezium images also allowed me to properly scale up the SC8 image to correspond to those of the SC11, and furthermore apply a correction to eliminate the field-of-view rotation inherent in the SC8 alt-az image.  Without the Trapezium formation, salvaging the 2012 image would have been way more complicated.”

Montambault said he combined the three images using Adobe Photoshop CS3 with all the corrections he could identify, “using layers of variable transparency to produce a unique image.”

“I slightly accentuated the three Sirius B detections in the image to make them more visible, given the dimming effect of the layers,” he noted. “I then applied a scaled transparent image of Sirius B’s orbit to check the fit. The fit was pretty good, especially for the 2016 and 2021 detections. A bit off for the 2012 detection, a bit too far back in the orbit, but not by much, and still on the orbital track itself.”

The judges were impressed with Montambault’s work in capturing Sirius B, one judge noting they “were very impressive to me.”

“This shows shows a lot of dedication, not to mention skill in actually catching that difficult target,” said another judge. “An interesting project.”

Messier 51, or the Whirlpool Galaxy, by Tim Doucette | Astrophotography | SkyNews
Messier 51 by Tim Doucette

Our honourable mention this week goes to Tim Doucette for his gorgeous image of Messier 51.

Also known as the Whirlpool Galaxy, the grand-design spiral galaxy’s smaller yellow companion, NGC 5195, has been passing by for hundreds of millions of years. Some astronomers believe the close encounter has tugged at the Whirlpool’s arms, triggering tidal forces and new star formation.

Doucette used a Celestron 14″ Edge with a Starizona Hyperstar (f/1.9), along with a ZWO ASI2600MC Pro to capture the image. Shooting on March 27, 2021, he said he captured 230 30-second exposures for a total integration time of about two hours. He gathered the data from his Deep Sky Eye Observatory in Tusket, Nova Scotia.

“At the centre of each galaxy is a supermassive black hole,” he wrote. “What impresses me the most about this image is how much detail I was able to resolve at 684mm focal length. Using special processing techniques to process the images in PixInsight (CFA drizzle, deconvolution, etc.) brings out some nice detail. It took over 24 hours for the computer to preprocess the data, then another three hours of my own time to put it all together.”

Prizes for the 2020-21 SkyNews Photo of the Week contest are sponsored by Sky-Watcher, Celestron, iOptron and The Royal Astronomical Society of Canada. Click here for more details on the prize packages that will be awarded to the best photos this year. 

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