“Definition” — of dust clouds, galactic arms, Hydrogen-alpha regions, the central core — is the key word to describe the Photo of Week winner on May 27, 2022, Steve Leonard’s capture of the Pinwheel Galaxy.

The Pinwheel Galaxy, also known as Messier 101, is located 25 million light-years away from Earth in the constellation Ursa Major. It is nearly twice the diameter of the Milky Way at 170,000 light-years across and is estimated to contain at least one trillion stars. Its spiral arms are sprinkled with star-forming nebulae, areas of intense star formation within giant molecular hydrogen clouds.

Leonard captured the image with a ZWO ASI1600MM and an Astro-Tech AT115EDT (f/5.6). He captured six hours of data — three hours in red-green-blue and 2.8 hours of luminance — from Bortle 8/9 skies in Markham, Ontario, in April 2022.

“I imaged this galaxy over two nights back in early April during the peak of galaxy season,” he wrote in his submission. “I’ll be looking forward to coming back to this one again next year, hopefully with more integration time and without using my focal reducer to try to catch even more detail.”

Honourable mention

The very honourable mention this week goes to Dan Kusz for yet-another beautiful capture of a rarely-imaged object, the Valentine Rose Nebula.

Kusz’s nicely-composed picture displays the rose-like features of the unusual planetary nebula, also known as Sh2-174.

A planetary nebula is usually created when a low-mass star blows off its outer layers at the end of its life, leaving behind a core that is called a white dwarf. Usually, the white dwarf can be found very near the centre of the gases and debris. But Sh2-174’s white dwarf is to the right due to the nebula’s interaction with the interstellar medium that surrounds it. 

Kusz captured the image with a ZWO ASI2600MM Pro on a Sky-Watcher Esprit 120 reduced to 647mm (f/5.4). He captured 15.75 hours of data from Vernon, British Columbia, shooting from February to May 2022. He collected Hydrogen-alpha, Oxygen III and red, green and blue data.

Kusz noted that Sh2-174 is one of the northernmost planetary nebulae, located about three degrees north of Alrai, or γ Cephei.

“Its strong northern declination means that it can be observed throughout the entire year,” he wrote in his submission. “I imaged this target while it was at was at its lowest point in the sky. It was a weird sight, seeing the telescope pointing at an object so low, giving me anxiety about a possible collision, as a meridian flip failed on one of the nights!”

He said cloudy skies kept him from collecting more data, and he decided to see what he could process with the data he had as to move on from this project.

“Not collecting any luminance data was my biggest regret, as there is a decent amount of faint dust in this region I wanted to incorporate, as well,” he wrote.

“I am really happy with the internal structures I picked up inside the ‘rose,'” he added. “I processed the image to highlight these areas and not oversaturate the entire region to keep the contrast up to bring out the details.”