This is the first of what will be many posts on this comet. Comet 12P/Pons-Brooks will be in the western sky in the evening for the next few months and could brighten enough to be visible to the unaided eye. Right now, however, it is quite dim at a magnitude of +9.0 and is located near the star Vega in the constellation Lyra.
Comet 12P/Pons-Brooks is a cryovolcanic comet. When exposed to the sun’s warmth the pressure within this cryomagma builds up until it triggers the release of gases, expelling icy fragments (and the gases) through cracks in the comet’s outer layer and into space. 12P has already had multiple bursts which have resulted in rapid brightening.
I ventured to Sunset Crater Volcano National Monument, an International Dark Sky Park, to shoot images of the comet. As noted above, it very close to the bright star Vega which made it very easy to find. My primary goal was to use my Nikon 180mm f/2.8 AIS lens, a legacy manual focus lens known for value in astrophotography and so that I could capture the full constellation. My secondary plan was to use the Nikon 200-500mm lens at its maximum zoom showing just Vega and 12P.
Owing to being a bit out of practice (it happens), both my focussing and star tracking were suboptimal. Something to work on for my next shoot.
Photographing a meteor shower is always about trade offs. If you shoot with an ultra-wide lens the meteors are small and you will likely miss some of the dimmer ones. But the wide angle view ensures that you cover a large portion of the sky.
Another option is to shoot with a lens that is in the “normal” range or even a telephoto. The disadvantage is the field of view is greatly reduced while an important advantage is that the lens will capture the dimmer meteors.
The Lens Aperture Area versus Angular Coverage Trade Because meteors appear in random location across the entire night sky, one might think that an all sky camera would pick up the most meteors. But this is not the case. Wide angle lenses mean short focal lengths and short focal lengths have smaller physical lens apertures, so collect less light. Thus, there is a trade between lens technology to collect a lot of light and angular coverage…
Another factor in meteor capture is where to point. If one points closer to the radiant then the angular velocity of a meteor decreases and the longer focal lengths are not impacted as much.
For several years I shot with wide-angle and ultra-wide-angle lens (28mm, 24mm, and 16mm). More recently, I been shooting with 50mm and 85mm lens. Last year, with the 85mm lens I captured one (1) meteor. But the detail was great!
We set up the camera on a star tracker, dialed in the settings, and then let it go taking continuous shots at ƒ/2.8, 30 seconds, and ISO 1600. The camera was pointed with the radiant in the lower left corner. Also visible in the composite is Andromeda Galaxy (M31) in the upper right. Meanwhile, we pulled out the camp chairs and leaned back to stare at the sky for a few hours.
We saw a few dozen meteors in about 2-1/2 hours and the camera with its smaller FOV captured considerably fewer. As the Moon rose above the horizon we packed it all away and drove home. Reliable reports indicate that meteor activity picked up considerably in the pre-dawn hours. We were happily asleep at that time.
The first image is a stack of the handful of shots containing meteors and downsized for this posting. The second image (full-size image), on the other hand, is a full-size crop of two meteors showing how much detail can be found when using a fast lens with a narrow field of view.