Tuesday, December 15, 2015

20151215 Comet C/2013 US10 Catalina

This comet is special: Aside from having both dust and gaseous tails, the comet’s speed has achieved escape velocity from our solar system.  These next couple of months are your only chance to see this particular celestial object.

This morning at 5:30am from my Fremont, CA backyard, I found the comet straightaway.  I first used 8x56 binoculars to sweep over from Mars (which has replaced Theta Virginis as a naked eye reference) to the field and could make out a moderately bright small fuzzy patch.  I then set-up my 8” f/7.25 reflector in the right area in my yard to see the comet, which was in a slice of sky between a tree and a neighbor’s house.  Again using Mars as an orientation point, I could make out Zeta Virginis and pointed the telescope to it, then made a quick hop to the comet, which was near Upsilon Virginis. 

At 42x the coma was fairly bright, round, bluish grey haze with a sharply brighter center.  After some time I could begin to make out a bulge on the edge of the coma, which would be the beginnings of a tail.  The comet was in the NW corner of a Sagittarius-shaped asterism, in the “spout.”

I read that the comet responds well to a SWAN band filter.  I was using a 35mm eyepiece for my initial observation, and hoped to use it for the filtered view since it would have an ideal exit pupil at 4.5mm.  But I could not get the filter to thread onto it, so switched to a 22mm eyepiece instead.  At 67x, 2.8mm exit pupil, the coma appeared brighter and larger, nearly reaching a nearby field star it did not reach in the unfiltered view.  I could just barely detect dual tails: an extremely faint blunt and about half a degree long dust tail, and an excessively faint and wispy thin one degree long ion tail—reminiscent of seeing the Eastern Veil Nebula in light polluted skies.    I’m guessing the higher magnification helped me see the dust tail, and the filter helped me see the ion tail.  But both were really tough.

Seeing and transparency, which had been average before, took a turn for the worse.  I had a look at Jupiter in case there were any transits happening (there weren’t), and had a view of Mars and Venus, both mushy.  At 6:10am I saw a long bright fireball meteorite near Hydra / Corvus, which left the faintest of smoke trails.   I then noticed a bright satellite in Leo, headed SE, and tracked it with my finderscope.  At times I was able to lead it into the center so it would rush through my eyepiece, a bright swift dot.  I followed it all the way to the horizon.  I’ve been looking for references today as to which satellite it was (ISS?) but so far have not identified it.

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