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C/2012 F6 (Lemmon)

Orbit by Kazuo Kinoshita

Image of comet Lemmon on 2013 January 26
Copyright © 2013 by R. Ligustri (Italy)

This image was acquired on 2013 January 26, while remotely using a Takahashi 90-cm refractor and CCD camera at the Siding Spring Observatory (Australia). This is a 300-second exposure.

Discovery

The Mount Lemmon Survey (Arizona, USA) reported the discovery of an asteroidal object on images acquired during 2012 March 23.21-23.30. The magnitude was given as 20.6-20.8. A follow-up observation by amateur astronomer Peter Birtwhistle (Great Shefford, Berkshire, England) using a 40-cm reflector and a CCD camera on March 23.9 revealed a diffuse appearance, with a diameter of 5 arc seconds and an extension of 9" toward PA 270 degrees. He gave the magnitude as 20.1. Birtwhistle's follow-up observation on March 25.0 revealed a slightly diffuse object with a coma measuring 9" by 4", with the longest axis toward PA 270 degrees. He said the magnitude was still 20.1.

Prediscovery images were found by G. V. Williams (in the survey archives of the Mount Lemon Survey (Arizona, USA) and Pan-STARRS 1 (Haleakala, Hawaii, USA). The three Mount Lemon images were obtained using the 1.5-m reflector and a CCD camera during 2011 December 28.35-28.38 and revealed a magnitude range of 19.5-19.9. The three Pan-STARRS 1 images were obtained using the 1.8-m refelctor and a CCD camera during 2012 January 28.45-28.50 and indicated a magnitude range of 19.8-20.6.


Early Orbit Calculations

The first orbit was calculated by G. V. Williams. He used 25 positions from the period of 2012 March 23-25, giving the perihelion date as 2013 August 11.18 and the perihelion distance as 1.74 AU. Williams published a revised orbit on April 3. This used 36 positions from the period of 2012 March 23-29, giving the perihelion date as 2013 March 25.28 and the perihelion distance as 0.74 AU. This orbit proved a very good estimation, as recent orbits using positions spanning 10 months reveal a perihelion date of March 24.52 and a perihelion distance of 0.73 AU. The comet is also moving in an elliptical orbit with a period of about 11 thousand years.

Historical Details

  • During the next few months, the comet slowly brightened as it approached twilight. It was last detected before becoming lost in the sun's glare on June 14, when H. Sato remotely imaged the comet using a telescope and a CCD camera at RAS Observatory (Mayhill, New Mexico, USA). He gave the magnitude as 19.0. The comet passed 0.7 degrees from the sun on August 25. The first observation made as the comet was exiting twilight was using a telescope and a CCD camera at iTelescope Observatory at Mayhill on October 14.50. The magnitude was given as 15.3.
  • The first visual observation came on ??
  • Nov 22 m1 11.3 20-cm L Juan Jose Gonzalez Suarez (northern Spain) coma 2.5' Dec 11 m1 10.8 11-cm L Rob Kaufman (Bright, Victoria, Australia) coma 2.5' Dec 12 m1 9.8 20-cm L Michael Mattiazzo (Castlemaine, Victoria, Australia) coma 6' Dec 17 m1 9.5 40-cm L Will Godward (Moonta, South Australia, Australia) coma 6.1' Dec 18 m1 9.4 25x100 bin Michael Mattiazzo (Castlemaine, Victoria, Australia) coma 6' Dec 18 m1 9.6 18-cm L Alexandre Amorim (Florianopolis, Brazil) coma 3' Dec 23 m1 8.7 20-cm L Juan Jose Gonzalez Suarez (northern Spain) coma 7' Jan 1 m1 8.6 7-cm R Alexandre Amorim (Florianopolis, Brazil) coma 3' Jan 2 m1 8.5 30-cm L Con Stoitsis (Caulfield, Victoria, Australia) coma 4' Jan 5 m1 8.0 7x50 bin Chris Wyatt (Walcha, New South Wales, Australia) coma 15' Jan 6 m1 8.2 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 12' Jan 8 m1 7.2 25x100 bin Juan Jose Gonzalez Suarez (northern Spain) coma 12' Jan 10 m1 8.0 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 6' Jan 10 m1 8.0 10-cm L Andrew Pearce (Nedlands, Western Australia, Australia) coma 6' Jan 10 m1 7.8 11-cm L Rob Kaufman (Bright, Victoria, Australia) coma 8' Jan 11 m1 7.9 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 5' Jan 11 m1 7.3 7x50 bin Chris Wyatt (Walcha, New South Wales, Australia) coma 9.5' Jan 12 m1 7.6 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 6' Jan 13 m1 7.5 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 10' Jan 14 m1 7.5 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 6' Jan 15 m1 7.1 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 8' Jan 16 m1 7.5 10-cm L Andrew Pearce (Middle Beach, Western Australia, Australia) coma 6' Jan 17 m1 7.4 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 7' Jan 18 m1 7.3 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 7' Jan 18 m1 7.3 10-cm R W. Souza (Sao Paulo, Brazil) coma 5' Jan 19 m1 7.1 10-cm L Andrew Pearce (Middle Beach, Western Australia, Australia) coma 8' Jan 19 m1 7.1 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 8' Jan 19 m1 7.2 11x80 bin W. Souza (Sao Paulo, Brazil) coma 8' Jan 20 m1 7.0 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 7' Jan 20 m1 7.0 10-cm L Andrew Pearce (Nedlands, Western Australia, Australia) coma 6' Jan 21 m1 6.9 20x80 bin W. Souza (Sao Paulo, Brazil) coma 10' Jan 21 m1 6.8 10-cm L Andrew Pearce (Nedlands, Western Australia, Australia) coma 7' Jan 22 m1 7.0 20x80 bin W. Souza (Sao Paulo, Brazil) coma 10' Jan 22 m1 6.9 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 7.5' Jan 23 m1 6.8 10-cm L Andrew Pearce (Nedlands, Western Australia, Australia) coma 7' Jan 24 m1 6.8 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 7' Jan 24 m1 6.6 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 7.5' Jan 24 m1 6.8 10-cm L Andrew Pearce (Nedlands, Western Australia, Australia) coma 7' Jan 25 m1 6.7 20x80 bin W. Souza (Santos, Brazil) coma 7' Jan 26 m1 6.7 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 6' Jan 28 m1 6.5 10x50 bin Alexandre Amorim (Florianopolis, Brazil) coma 10' Jan 29 m1 5.8 11x70 bin Con Stoitsis (Caulfield, Victoria, Australia) coma 7.5' The comet will attain its most southerly declination of -87 degrees on February 5.

    Additional Images

    Image of comet ISON on 2013 January 16
    Copyright © 2013 by R. Ligustri (Italy)

    This image was acquired on 2013 January 16, using the remote 45-cm reflector and an FLI PL6303E CCD camera at Mayhill, New Mexico. The comet is indicated by the tick marks to the right of the middle of the image. [This is a crop of the original image]

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