Comet C/2021 A1 (Leonard)

 
Discovered by G. J. Leonard at the Mount Lemmon Observatory on January 3 2021 when it was mag 19 and about 5 AU from the Sun. It was closest to Earth (0.233 AU) on December 12, 2021, and reached perihelion on January 3, 2022, at a distance of 0.615 AU from the Sun. In early December it just achieved naked eye visibility, but later that month it underwent several outbursts to brighten to 3rd magnitude before fading slightly and then steadily. Early January, it again underwent a number of outbursts as it moved away from the Sun. Later observations failed to find a central condensation indicating that it had likely disintegrated during the first sequence of outbursts. During December and January it was well-placed for southern hemisphere observers who remarked on the beautifully structured tail which extended to over 60o in deep stacked images. 

It put on a very fine show.

 

2021 December 20: a nice early Christmas present! Photographed against the stars of Microscopium when about magnitude 3, but low altitude. Canon 5D II + 500mm lens + 1.4X extender, on an NEQ6 Pro mount tracking the sky. 

A series of fifty 20sec exposures (~16 mins total) at f7.1 and ISO 1000 were aligned on the comet, while six of the images (2 mins total) were separately aligned on the stars. These were combined to optimise the comet against the star field; field of view 3° x 2°, north is to the right. 

2021 December 21: when at ~mag 3.5 one day after outburst against the stars of Microscopium. Very nice fine structures in the ion tail. Canon 5D II + 500mm lens + 1.4X extender, on an NEQ6 Pro mount tracking the sky. 

A series of fifteen 15sec exposures (~4 mins total) at f8 and ISO 6400 were aligned on the comet, while four of the images (1 min total) were separately aligned on the stars. These were combined to optimise the comet against the star field; field of view 3° x 2°, north is to the right. 

2021 December 27: about magnitude 5 when photographed against the stars of Microscopium. The ion tail is clearly seen as a narrow structure extending to the top of the field. 

Takahashi TOA-130 with 0.7X focal reducer + Takahashi EM-200 Temma2 mount + SBIG STL11000M camera, fl=720mm, f5.6; 160 secs each of R, G and B filtered frames (8 min in total) were calibrated, aligned and combined; field of view 2.9° x 1.9°, north is to the right. 
2021 December 28: about magnitude 5 when photographed against the stars of western Piscis Austrinus. Another outburst has resulted in major changes in the ion tail, including a disconnection event about 3/4 of the way along the tail.

Takahashi TOA-130 with 0.7X focal reducer + Takahashi EM-200 Temma2 mount + SBIG STL11000M camera, fl=720mm, f5.6; 8 x 90 secs exposures of R, G and B filtered frames (36 min in total) were calibrated, aligned and combined; field of view 2.9° x 1.9°, north is to the right. 
2021 December 29: about magnitude 5 when photographed against the stars of western Piscis Austrinus. At least two fine filaments are visible in the ion tail.

Takahashi TOA-130 with 0.7X focal reducer + Takahashi EM-200 Temma2 mount + SBIG STL11000M camera, fl=720mm, f5.6; 6 x 120 secs exposures of R, G and B filtered frames (36 min in total) were calibrated, aligned and combined; field of view 2.9° x 1.9°, north is to the right. 

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