C/2015 G2 MASTER


Closest to Earth on 13 May 2015 at 0.47AU
Closest to Sun on 23 May 2015 at 0.77AU
Maximum magnitude 6.0 in May 2015

The story began on the morning of March 31st, when Rob Kauffman (Bright, Victoria) and I both imaged comet 88P Howell, in the morning sky before dawn.
Little did we know that a new, undiscovered comet was situated only a couple of degrees away from 88P!
Then a week later on April 7, D. Denisenko reported the discovery of a comet on images taken with the
Mobile Astronomical System of TElescopic Robots at the South African Astronomical observatory. (Acronym for MASTER)
The comet was posted on the Possible Comet Confirmation webpage as M503ujx.
I checked my 88P images, but the new comet was located just outside my field of view.
Rob Kauffman, on the other hand, had the comet at the edge of his image but hadn't noticed it at the time!
Rule of comet photography - always scan your images for any potential interlopers.



Comet C/2015 G2 MASTER (labelled M503ujx) seen in the same field of view as 88P Howell on 2015 April 8 at 19:15UT
My visual magnitude and coma-diameter estimate on April 8.80 UT was 9.7 and 2'.5, using a 20-cm reflector in moonlight.
The comet appeared more condensed but slightly smaller and fainter than comet 88P, which lied 2.5 deg to the northeast.

The comet brightened rapidly after discovery, as it approached Earth and Sun.
I estimated it at magnitude 9.7 on April 8,
then magnitude 8.5 on April 19, when situated less than a degree away from the Helix nebula,


By the start of May 2015, the magnitude 7.1 comet was situated in Sculptor, in the hour before dawn.
Moonlight interfered from the 3rd but fortunately the comet moved rapidly into the darker evening sky from May 10
and was visible in the constellation of Fornax, low in the southwest after sunset for those observers in the southern hemisphere.
An interesting deep sky rendezvous occurred with the Fornax galaxy group on the 13th, near NGC 1350

The comets maximum brightness of magnitude 6.0 occurred just after closest approach around May 15th.
Although the ion tail was quite faint visually, I managed to photograph a tail 6 degrees in length.




The comets rapid easterly motion took it through Eridanus on May 14, Lupus on May 17, Canis Major on May 22, and Monoceros on May 26.
Moonlight interfered once again from May 22.

As June began, the magnitude 7.4 comet was situated in Monoceros, in the western sky after dusk, but moonlight interfered with viewing until the 4th.
The comet crossed into Canis Minor on the 8th, and was 3 degrees SE of Procyon on the 14th.
By this time the comet had faded to magnitude 8.5.
Moonlight started to interfere by June 20, and the show was virtually over for comet MASTER as it sank towards evening twilight.


Location chart May 2015


Location chart June 2015