Over the past couple of years, astrophotographers and observers alike have been graced with approximately one brilliant comet per year. In 2020, we had Neowise, 2021 Leonard, and 2022 comet C/2022 E3 (ZTF).
Comet C/2022 E3 (ZTF) was discovered on March 2, 2022, by the Zwicky Transient Facility – hence the acronym ZTF attached to the comet’s name. The comet was incredibly dim when this discovery was made, yet over the next few months, as it approached the sun, it would brighten substantially. By late January 2023, the comet reached perihelion, which is its closest point to the sun along the trajectory. Going into February, the comet made its closest approach to Earth, 42 million kilometers (26 million miles) distant, which provided a brief window for naked-eye observation in proper viewing conditions.
Due to the moon, clouds and general light pollution, we were unable to visually spot the comet. However, this did not stop us from trying to capture it! Ethan spent one night in a Bortle 4 location imaging C/2022 E3 (ZTF). Years of using star-hopping to find deep space objects with a non-motorized telescope allowed him to acquire the hidden comet in little time. He then quickly set off to capture an hour of data before the clouds rolled in. It was our one chance to document the comet’s close approach. NASA’s Jet Propulsion Laboratory calculated an orbital period of 50,000 years, yet it is possible that gravitational perturbations may have increased the comet’s period or potentially sent it on a trajectory out of our solar system forever.
With the comet data now acquired, an even more challenging step loomed ahead – processing. Unlike nebulae and galaxies, which are many light years away (trillions of kilometers), the comet is relatively close to Earth at only a few million kilometers. This results in a much larger relative motion between the target and the background stars. So, if you were to stack the comet-like nebula, the comet would lose its detail and blur across the image. This means the comet and stars need to be separated from the light frames and stacked individually. It took considerable time to get the entire image processing workflow just right, yet we believe it was worth the effort to share this beautiful otherworldly object with all of you!