C/2012 F6 Lemmon

The Great Southern Binocular Comet of 2013
Closest to Earth:  6 Feb 2013 at 0.98AU
Closest to Sun:   24 March 2013 at 0.73AU
Maximum magnitude: 4 in mid March 2013
Orbital Period: 9,136 years

2013 March 14.42 UT
Comet C/2012 F6 Lemmon with edge on spiral galaxy NGC 55 in Sculptor.
The ion tail stretches 9 degrees in this photo, passing through Kappa Phoenicis.
3x2 minute stack, Canon 60Da and 100mm zoom lens. Visual estimate 4.8.

Discovered by the Mount Lemmon survey on 23 March 2012, comet Lemmon was a surprise packet.
Only predicted to reach magnitude 9 in March 2013,  I was already estimating it at magnitude 10 during mid December 2012.
At this rate of brightening, Comet Lemmon was on course for a naked eye performance for southern observers during March 2013.
Even better, it would appear at the same time and vicinity as C/2011 L4 PANSTARRS. A rare double comet show!

Perihelion occurred on March 24 at 0.73AU. The orbit is of long period (about 9,000 years) so this was not the comets
first visit through the inner solar system. This would explain why the comet performed better than expected.
On 2013 January 1, the magnitude 8 comet was situated in Centaurus, near the Hydra border, best observed after midnight.
It travelled southwards over a degree per night, becoming circumpolar on the night of 2013 Jan 17, when the now magnitude 7 comet
was within a degree of Gamma Crucis. Moonlight started to interfere however, as well as the bright milky way background.
It was best observed in the predawn sky.

On February 1, the now magnitude 6.0 comet was situated in Chameleonis, near Delta Octans, and observable all night.
On Feb 6, it was only 3 degrees away from the south celestial pole.
On the night of Feb 9, the now mag 5.5 comet was within a degree of Beta Octans (mag 4.1).
On Feb 14, the comet moved into Tucana and was 4 degrees to the west of globular cluster 47 Tuc and the Small Magellanic Cloud,
 making for a spectacular photo opportunity. The ion tail appeared at least 5 degrees long.
By Feb 16, moonlight interfered with evening sky observing but the comet continued to be observable in the morning sky (until the 24th),
where C/2011 L4 PANSTARRS was also visible.
Switching back to evening viewing, the now magnitude 5.0 comet entered Phoenix on Feb 24 and by the end of February,
 was joined by C/2011 L4, although moonlight interfered until March 2.

Comet Lemmon peaked at magnitude 4.5 in the middle of March and put on quite a show, for those situated in dark sky sites.
Considering it was only expected to reach 9th magnitude, this was no Lemon!
Made predominantly of gas, the ion tail could be traced for at least 5 degrees through binoculars and at least 10 degrees on photographs.
Rapid variations in the ion tail were visible from night to night, due to interactions with the Solar wind.

The comet approached evening twilight during March and was lost March 24, reappearing in the morning sky during early April.
Northerners picked up the comet in early May when it had faded to magnitude 6.

Below are my observations in chronological order

2013 March 11.42 UT
Comet C/2012 F6 Lemmon has rendezvoused with edge on spiral galaxy NGC 55 in Sculptor.
The 8th magnitude galaxy is some 6 million light years away whilst 4th magnitude comet Lemmon is a mere 10 light minutes.
details: Canon 60Da and EF 300mm zoom lens. 4x2 minute stacked exposure.


2013 March 5.43 UT
Comet is adjacent to Eps Phe and appeared slightly fainter than this star to the unaided eye. Estimated magnitude 4.5.
Through 8x40mm binoculars, the ion tail is traceable to 4 degrees in PA 155. The tail length in this 6 minute photo is 7 degrees.


2013 March 1.43UT
The ion tail shows up impressively in this 8 minute exposure at 300mm. Canon 60Da.


2013 March 1.43UT
A wide field shot at 120mm showing a 10 degree long ion tail. This appears to be the maximum length obtained.
Eta Phe is bright star at top left. Naked eye estimate 5.0


2013 Feb 28.41 UT
Canon 60Da, 3x2 minute stack. 300mm zoom lens, cropped. Magnitude 5.0
The ion tail is much more intense than in the previous week.

2013 Feb 15.74 UT
Canon 60Da, 4x2 minute stack. 300mm zoom lens, cropped. Magnitude 5.2
The ion tail is at least 5 degrees long.
Globular cluster 47 Tuc, the Small Magellanic Cloud and satellite flare make for a great photo!

2013 Feb 8.74 UT
Canon 60Da, 5x2 minute stack. 300mm zoom lens, cropped. Magnitude 5.5
The ion tail is at least 3 degrees long in PA 165.

2013 Feb 2.5UT
Canon 60Da, 5x2 min stack, 300mm zoom lens, cropped. FOV is 4.5 degrees wide. Ion tail is about 3 degrees long.


2013 Feb 2.5UT
10x10 sec exposures, C11 + MX7c CCD camera.


2013 Feb 1.5UT
Canon 60Da, 5x2 min stack, 300mm zoom lens, cropped.
2 degree ion tail is visible. Comet was at mag 5.7 and visible to unaided eye using averted vision.


2013 Jan 27.5UT
Canon 60Da, 10x20sec stack, C11 telescope at F6. Full moon interference. Mag 6.1

2013 Jan 19.7 UT
Canon 60Da, 3x2 minute stack. 100mm zoom lens, cropped. Comet is inside the Southern Cross. Mag 7.0



2013 Jan 16.5 UT
Canon 60Da, 5x2 minute stack. 300mm zoom lens, cropped. Gamma Crucis is on the right.

 


chart showing comets path

My visual obs below indicating a peak brightness of 4, as opposed to MPC predicted peak of 9.
My calculated formula of m1=4.5, and slope n=5