Perseïd Meteor
Perseïd meteor - Click here for full resolution
The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle that are usually visible from mid-July to late-August. The meteors are called the Perseids because they appear from the general direction of the constellation Perseus and in more modern times have a radiant bordering on Cassiopeia and Camelopardalis. The stream of debris is called the Perseid cloud and stretches along the orbit of the comet Swift–Tuttle. The cloud consists of particles ejected by the comet as it travels on its 133-year orbit. Most of the particles have been part of the cloud for around a thousand years. However, there is also a relatively young filament of dust in the stream that was pulled off the comet in 1865, which can give an early mini-peak the day before the maximum shower. The shower is visible from mid-July each year, with the peak in activity between 9 and 14 August, depending on the particular location of the stream.
During the peak, the rate of meteors reaches 60 or more per hour. They can be seen all across the sky. However, because of the shower's radiant in the constellation of Perseus, the Perseids are primarily visible in the Northern Hemisphere. As with many meteor showers the visible rate is greatest in the pre-dawn hours, since more meteoroids are scooped up by the side of the Earth moving forward into the stream, corresponding to local times between midnight and noon. While many meteors arrive between dawn and noon, they are usually not visible due to daylight. Some can also be seen before midnight, often grazing the Earth's atmosphere to produce long bright trails and sometimes fireballs. Most Perseids burn up in the atmosphere while at heights above 80 kilometres.
source: Wikipedia
NGC/IC:
Other Names:
Object:
Constellation:
R.A. (radiant):
Dec: (
Peak activity:
n.a.
n.a.
Meteor shower
Perseus
3h 13m
+58°
12 Aug
Conditions
Peak of the Perseids is around August 11-12. This year the moon was down when it got dark, so conditions were good. On August 11 a short trip just out of town (Groningen, The Netherlands) gave just enough distance from the city lights to do some meaningful photography. Although the glow of the city still remains visible in the photo. Weather conditions were generally good, with totally clear sky and around 15 °C temperature after midnight. Humidity was quite high though at 95%, causing a little bit of coma around some bright stars.
Equipment
Images were captured with a regular mirrorless camera and diagonal fish-eye lens of 15mm. This provided a diagonal field of view of 180°. This is a recently released lens, and the Perseids were a good target to test this lens out for astrophotography. No mount or tracker were used. Lens was pretty much pointed straight up, because of its huge field of view.
Lens
Mount
Camera
Filters
Guiding
Accessoires
Software
Sigma 15mm f/1.4 DG DN diagonal fisheye ART-lens for L-mount
Stationary Arca-Swiss P0 ballhead on Gitzo GT3543XLS tripod
Leica SL3
n.a.
Unguided
n.a.
PixInsight 1.8.9-3, Adobe Photoshop 24.0.1, Capture One
Imaging
To avoid star trailing in a static setup, the shutter speed should not be too long. The often referred to 500 rule (maximum shutter speed is 500/focal length of lens) is in my experience much too tolerant and I often use the 250 rule as a starting point. In this case I chose 10s exposures. ISO was set at 800, which gave enough detail in the final image. Focusing was done manually by zooming in onto a bright star. Once focus was achieved, this was locked on the lens (a specific astro-feature of this lens). The camera was set to interval shooting, so it kept shooting 10s exposures until stopped.
The Sigma 15mm f/1.4 DG DN diagonal Fisheye lens is an interesting new lens, designed with Astrophotography in mind. By design, rectilinear extreme wide-angle lenses always have distortion towards the edges of the frame, as they are designed to keep straight lines as straight as possible. For astrophotography, such distortions show as elongated stars in the corners, even if there is no coma. A diagonal fisheye lens is not designed with such corrections and captures the image as a kind of a dome. For astrophotography this is a good thing. Nico Carver from Nebula Photos has reviewed this lens on his YouTube channel and demonstrated much better star shapes in the corner wide-open as compared to an equivalent 14mm rectilinear lens. The lens was used here coupled to a Leica SL3 camera, which is equipped with the well known 60MP Sony IMX-455 sensor.
Processing
Images were recorded in DNG format and could be used straight out of camera in PixInsight. No dark and/or flat frames were recorded, so no calibration was done. A total of 484 images were acquired over a 1 hour and 45 minute period. Eleven frames had recorded a meteor. One of them was by far the brightest and has been processed here as the main image. The 10 preceding frames were registered to the main image and integrated to form the backdrop image. Corners with pieces of landscape were cropped out. There was a huge gradient present in the image, representing the glow from the nearby city. The Automatic DBE script from SetiAstro was used to eliminate some of this gradient, but this could not remove the gradient entirely. It was not possible to platesolve the image, so a regular ColorCalibration and BackgroundNeutralization were applied. BlurXterminator was used to tighten up the stars. The image was non-linear to begin with, but GHS was applied to bring out as much detail and contrast in the Milky Way as possible while keeping the background nice and black. As a final step NoiseXTerminator was used to smoothen the noise out.
The image was now separated into a starless and a stars-only image, using StarXTerminator. Both images were exported to Photoshop as a 16-bit TIF for further processing. A few bright stars had some blue halo around them, due to the extreme high humidity. The meteor itself also exhibits some halo. The halo’s were removed using the content-aware spot healing tool on the starless image. Also a further attempt to minimise the gradient to the left side of the image was made by overlaying a gradient. Final image was now established by combining the starless and stars-only image as layers and ‘paint’ the meteor on it from the main image using a simple mask.
An animated GIF of meteor and dust/gas trail that remained visible for over a minute. Eight images of 10s each, covering about 1.5 min.
The live view of the meteor was extremely impressive, and the dust/gas left behind was visible for a minute after the meteor itself had disappeared. The subsequent images showed this dust/gas cloud slowly disappear. To demonstrate the effect, a total of 8 images were cropped tightly around the meteor, put in the right order as layers in Photoshop and exported as an animated GIF (see above).
Processing workflow (click to enlarge)
This image has been published on Astrobin and was displayed during the Dutch 8 o’clock news weather report of 12 August 2024 (22:50).
