C/2015 ER61 PANSTARRS
Closest to Earth on 2017 April 19 at 1.18AU.
Closest to Sun on 2017 May 9 at 1.042AU.
Maximum magnitude 6 in May 2017.
Orbital period: 7,763 years
Discovered as an asteroid but later shown to display
cometary activity, ER61 was not well placed from Earth's perspective,
closest at 1.17AU on April 20, however the comet was intrinsically bright (absolute magnitude about 6.5)
C/2015 ER61 was of long period, so had the potential to become brighter than expected, peaking at magnitude 6 or 7 during May 2017,
and well situated for southerners in the morning sky.
At the start of March 2017, the magnitude 10 comet was seen trekking slowly eastwards through Sagittarius, in the morning sky.
It was 1 degree north of globular cluster M28 on the morning of March 8. Moonlight interfered from March 11.
Above: 2015 ER61 PANSTARRS on 2017 March 18
By the morning of March 28, the comet traversed into Capricornus, brightening to magnitude 8.5.
At the start of April 2017, the magnitude 8.0 comet was situated in Capricornus, high in the East before dawn.
Above: Pre-outburst, comet appeared magnitude 8.3 through 25x100mm binoculars with a short tail.
On 2017 April 4, the comet experienced an outburst of 2 magnitudes, when
it was seen to brighten from magnitude 8 to 6 in a 24
below C/2015 ER61 PANSTARRS outburst on April 4 - 2 orders of magnitude brighter.
Below: Post-outburst, comet appeared magnitude 6.2 through 8x40mm
Moonlight interfered from the morning of April 10.
The magnitude 6 comet returned to Capricornus on the 13th, then back into Aquarius on the 19th.
By the morning of April 24th, moonlight no longer interfered, and the now magnitude 7.5 comet was a couple of degrees to the north of Rho Aqr.
Below: C/2015 ER61 PANSTARRS on 2017 April 28.
Since the outburst in early April ,the comet faded to pre-outburst stare, magnitude 7.5, but sported an ion tail 2 degrees long in this photo.
At the start of May 2017, comet 2015ER61 shone at magnitude 7.5, best observed in the hour before dawn.
On the morning of May 8, the comet is 30' NW of Kappa Psc, in the circle of Pisces.
Moonlight interferes from May 10 to May 24.