Astro Image

The Apparition of C/2023 A3 (Tsuchinshan–ATLAS)

Comet C/2023 A3 (Tsuchinshan–ATLAS) did not become a daylight comet as some had predicted — nevertheless the dirty-snowball put on a fine show in the twilight skies. This visitor from the Oort Cloud of icy bodies at the edge of the solar system was the third comet discovered in January 2023 (hence the designation C/2023 A3). It was closest to the Sun at perihelion on September 27, 2024 at a distance of 0.39 AU and magnitude of at least -4 — though very few saw or imaged it.

This gallery of Comet C/2023 A3 images contains views of the comet from late September to early November and highlights the changing nature of the object.

September: Pre-Dawn Comet
Most of the images on this blog were taken when the comet transitioned into the evening sky after it rounded the Sun and began the long journey back to the Oort cloud. This gave imagers the luxury of setting up their gear in the warmth of daylight and the time to spot the comet in deepening twilight and start experimenting with exposures. The image below, however, was taken by a hardier soul: someone that camped out at the frigid altitude of 11,700 feet elevation to catch the comet while still in the dawn sky. Jeremy Evans had to race the Sun to image the comet — just a few degrees above the horizon — as the twilight reached ever higher to erase the fragile contrast between the comet and sky. “This was a challenge to catch” says Jeremy, “fortunately it appeared above the clouds just before the sun washed it out.”

Comet C/2023 A3 (Tsuchinshan-ATLAS) in the dawn sky by Instagram user Jeremy Evans . All rights reserved. Used by permission. The Tele Vue-NP101is APO Nagler-Petzval Refractor was fitted with Large Field Corrector (LCL-1069) and ZWO ASI2600MC, APS-C sized, cooled color camera. Focusing was done with ZWO EAF electronic focuser. The entire setup was mounted to a Losmandy equatorial mount. Exposure was 3 seconds at medium gain taken at 11,700 feet elevation, with perfect weather and dark Bortle 1 skies on Sept. 30, 2024.

Mid-October: Anti-Tail and Comet / Cluster Conjunction
Bill Fallon caught the comet showing an anti-tail as it sailed by globular cluster M5 in Serpens. The comet had crossed the plane of the Earth’s orbit on October 14th which made visible debris too large to be blown away by the solar wind. This debris appeared from Earth as an anti-tail extending from the head of the comet. Bill’s image was an AstroBin “Top Pick” nomination.

C/2023 A3 (Tsuchinshan-ATLAS) passing M5 by AstroBin user Bill Fallon. All rights reserved. Used by permission. Tele Vue-NP127is APO Nagler-Petzval Refractor with 0.8x reducer and FLI Atlas focuser was used for imaging with QHYCCD QHY268 M camera. All hardware carried on Software Bisque Paramount MYT mount. Imaged through Astronomik Type 2c 50mm red, green and Blue filters with subframes of 20×30″ for each filter. Total integration time on the comet was 30-min. Software used was Pleiades Astrophoto PixInsight. Imaged Oct. 15, 2024 from Temecula, CA.

A Tail of Three Comet Tails

Three tails of a comet. Credit: Roger Dymock (CC BY-SA 3.0).

We often marvel at a comet’s “tail,” but in reality comets have three tails. What are these tails? They have to do with the composition of the comet and the environment it is passing through. Fred Whipple’s popular model of a comet as a “dirty snowball” speaks to the typical comet’s composition of rock, dust, and volatile compounds such as water ice, frozen carbon oxides, ammonia, and some hydrocarbons.

The dust tail arises when the frozen volatiles are evaporated by the Sun: solar radiation pushes the liberated dust grains away from the Sun. The stream of dust reflects sunlight and appears as a long tail that can be millions of kilometers in length and sometimes quite broad. We know the Sun is causing this because the comet, whether approaching or receding from Sun, always has a dust tail pointing away from the Sun. On long tails, the momentum of the dust in the direction of orbit causes the tails to curve.

High energy ultra-violet rays from the Sun knock electrons off the gas atoms to create positive ions. These ions follow the path of the charged particles from the solar wind to form the ion tail that always points away from the Sun. Since ionized carbon molecules emit blue light, this is the prominent color of the tail. Changes in the solar wind can cause disconnection events in the ion tail where a section of that tail is pinched off and ripped away from the comet.

Large particles left behind by the comet are less impacted by solar radiation and remain in the orbit of the comet. If a visible comet crosses the plane of Earth’s orbit, and there is a sufficient density of particles, this edge-on view reveals this debris as a spike extending in front and behind the comet’s path of motion. Usually, only the anti-tail spike, opposite the dust tail, is prominent as the other is obscured by the dust tail. A few days on either side of this time period the anti-tail will look shortened and at an angle to the ion tail. Meteor showers happen when the Earth passes through these discarded particles that continue to orbit the Sun as the comet does.

Late-October: Less Lunar Interference
The Moon was full on October 17th which made it hard to image the comet. But just five days later, the Waning Gibbous was only 64% full, and rose hours after sunset. Guangyan Gao not only had to wait for the moon to be out of the early-evening sky, but clouds too.

“After two weeks of clouds in Seattle, there was finally a break in the weather. In an effort to try to get a good image of the comet, I made my way over to the mountain pass to try to catch a final glimpse of the comet. While it had dimmed considerably to around magnitude 4.5, with no more full moon in the sky, it was still a beautiful naked-eye object (even more amazing through binoculars). Through my f/4 Newtonian telescope, the darker sky allowed me to capture significantly more detail in in the comet’s tail, and the Paracorr-2 helped ensure pin-point stars across the entire field.”

Guangyan’s image below is an AstroBin “Top Pick” nomination.

Comet C/2023 A3 (Tsuchinshan-ATLAS) by AstroBin user Guangyan Gao . All rights reserved. Used by permission. Taken with Tele Vue 2″ Paracorr Type-2 (VIP-2010) on GSO 6″ f/4 Imaging Newtonian with ZWO ASI2600MC Pro camera on iOptron HAE29 mount with Ecoflow RIVER 2 Portable Power Station and ZWO ASIAIR Mini controller. Exposures of 45×60″ for a total integration time of 45′ taken on Oct. 22, 2024 from Gold Creek Pond, Snoqualmie Pass, WA. Software used was Adobe Photoshop, Pleiades Astrophoto PixInsight, and Russell Croman Astrophotography BlurXTerminator.
2 inch Paracorr Type-2
VIP-2010 Parracorr

About 2″ Paracorr Type-2 (VIP-2010)

Our highly versatile 2″ Paracorr Type-2  comes with a “Tunable-Top” for visual use. It can handle both 2″ and 1¼” eyepieces with the included 2″-1¼” adapter. The Tunable-Top feature moves the eyepiece up and down to maintain the proper eyepiece field-stop to Paracorr lens distance for optimal coma correction. For f/3 Dob/Newts, the Paracorr Type-2 tightens star images at the edge of the field of view 25-times smaller than without coma correction.

Paracorr Type-2 Spot Size vs Airy Radius

You can separate Paracorr’s optical assembly from the Tunable-Top and use it with Tele Vue Imaging System components to permit imaging with DSLR and CCD cameras. APS size formats 27mm-diameter or smaller are recommended to minimize field vignetting. (BIG Paracorr Type-2  is the 3″ version of the Paracorr designed for imaging with fast scopes and big chips.) Ideal for mirrors as fast as f/3, this is an essential accessory for both observing and wide-field imaging through fast Newtonians. Looking at the image on the right, the VIP-2010 Paracorr Type-2 system includes: 2″-1¼” adapter (top), Tunable-Top (middle), and Paracorr Type-2 body (bottom).

Click the Paracorr Type-2 Spot Size vs Airy Radius diagram to quantify how well the Paracorr-Type 2 series banishes coma for various focal ratio parabolic reflectors.  For each f-ratio shown, the curve in the diagrams indicates the RMS radius of a star image in microns from the center to the edge of the field with the 2″ Paracorr Type-2  installed. The shaded yellow area indicates spot sizes that fall below the diffraction limit for each given f-ratio — the Airy Disc Radius — is the calculated resolution limit radius of a distant star image and is indicated by the horizontal line at the top of the shaded yellow area. Notice that the theoretical spot size with the Paracrorr Type-2 is below the Airy Disc radius in the fastest mirrors. Except for the furthest reaches of the field in an f/3 scope, the spot size is still diffraction limited.  Just compare the spot size at the same point in the field with an uncorrected parabola — see the diagram on the right side labeled Spot Sizes for Parabola Alone.

Bill Fallon’s Tele Vue-NP127is also did a fine job on October 25th when the moon was in the last-quarter phase and rose very late at night.

C/2023 A3 (Tsuchinshan-ATLAS) Oct252024 by AstroBin user Bill Fallon. All rights reserved. Used by permission. Tele Vue-NP127is APO Nagler-Petzval Refractor with 0.8x reducer and FLI Atlas focuser into QHYCCD QHY268 M camera. All carried on Software Bisque Paramount MYT mount. Imaged through Astronomik Type 2c 50mm red, green and Blue filters for 20×60″ each filter. Total integration for comet was 1h with separate 15sec exposures for stars. Software used was Pleiades Astrophoto PixInsight. Imaged Oct. 25, 2024 from Temecula, CA.

November 1st: New Moon and Fading Comet
At the start of November, the comet had a 56° elongation from the Sun. It was no longer a race against time to image the comet before it set. The converse was that at 1 AU distant from the Sun, it wasn’t the bright comet it was a month earlier. The new moon on November 1st signaled the start of a final opportunity to image the comet before the brightening moon would blot it from the sky. Ryan Noonan used his Paracorr equipped Newtonian to both view and image the comet on that date: “I’d had a great experience with the Paracorr, both for visual as well as for imaging!”

C/2023 A3 Tsuchinshan – first successful comet attempt by AstroBin user Ryan Noonan. All rights reserved. Used by permission. Imaged using Tele Vue 2″ Paracorr Type-2 (VIP-2010) on 10″ f/4.5 Newtonian with OGMA AP26MC camera all carried on Losmandy G11 / G11G mount. Exposures through Chroma 50mm Red, Green, and Blue filters for 3×300″(15′) each color for a total of 45’ minutes. Taken November 1st from 7:00pm to 7:45pm. Software used was Adobe Photoshop, Pleiades Astrophoto PixInsight, and Stefan Berg’s Nighttime Imaging ‘N’ Astronomy (NINA). Taken from Los Alamitos, CA.

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