[BAA Comets] Fw: [comets-ml] Re: New Comet C/2017 E4 (LOVEJOY)

Tue Mar 14 13:50:56 GMT 2017

----- Forwarded Message -----
 From: "terryjlovejoy at yahoo.com [comets-ml]" <comets-ml at yahoogroups.com>
 To: comets-ml at yahoogroups.com 
 Sent: Tuesday, 14 March 2017, 12:01
 Subject: [comets-ml] Re: New Comet C/2017 E4 (LOVEJOY)

    Thank you everyone for your kind words, and of course to the people that sacrifice their spare time to get out there and do followup observations on new comets like this.

The latest comet, C/2017 E4, was found on a set of 3 images made on the morning of March 10 (Local time) in the constellation of Sagittarius.   Although my 6th discovery, this was the first discovery with the Hyperstar 14" Celestron Schmidt Cassegrain telescope.  However, because the field of view is now smaller I must now make shorter exposures, and more of them, to cover similar amounts of sky as possible.   However, I felt the extra aperture have has more than compensated especially since my location experiences quite bad light pollution being just 18 km from the centre of Brisbane, a city of more than 2 million people.
Back to the comet, it was found using MOD (Moving Object Detection) a computer program I wrote that searches sets of images for moving objects like comets of asteroids.  I tend to run MOD with very high sensitivity, which means it will identify anything remotely resembling a moving object, resulting in mostly false positive detection's.  In fact in crowded star-fields this can be as high as 90% false positives and so  I must examine each detection manually.  Nevertheless, this is huge time saver compared to examining the entire image manually. That morning a lot of the fields were in the milky way I had a large number of false detection's I had to examine, and there were also at least a dozen asteroids, but finally there was one object that had a definite coma and I knew almost certainly a comet.  I then did some checks against known asteroids/comets plus some checks to eliminate internal optical reflections as a cause for the detection.   This all checked out so I was certain of a new comet at this point.
 I then sought independent confirmation from another observer, and looking at Messenger I could see Cristavao Jacques in Brazil was online, so I contacted him, but unfortunately dawn had started and he had closed up the observatory so there was no luck there.  I then contacted Michael Mattiazzo and he was able to get a confirmation image not long after from a remote telescope in New Mexico.  This was all well within the 24 hours of the actual discovery images, which is probably a record for me!   The comet was then posted on the Possible Comet Confirmation Page and astrometry started to stream in over the next few days and within 3 days the orbit was known with enough certainty for it to be designated as C/2017 E4.  The orbit indicates - unfortunately - this is an intrinsically small comet that probably stay quite faint (and it could even disappear altogether) but we can always hope for a better display.
Terry Lovejoy

  __._,_.___     Posted by: terryjlovejoy at yahoo.com     
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