Saturday, December 26, 2015

Comet Catalina C/2013 US10

I had another look at the comet this morning.  I slept fitfully during the night and decided to get up when I woke suddenly at 4:30am.  The full moon was declining to the west, and I hoped since it was opposite the comet its light would not wash it out -- this hope proved unfounded.  Seeing seemed very good, and transparency was pretty good considering some high clouds or fog about.

Using Arcturus as a starting point I quickly found the comet by hopping to 15 Bootis, which turns out to be a widely separated pair with a pretty, bright yellow primary.  I saw the comet first in the eyepiece (31mm 48x 1.7 degree TFOV), following 15 Bootis about a third of a degree, looking like a faint unresolved globular cluster.  The coma was large, and brighter with averted vision, but I could not see the nucleus.  I looked through the finder and saw a very faint patch only after tapping the scope.

Using the same eyepiece with the comet filter, I could see the faintest of a thin tail trailing to the south west -- which seems to be the wrong direction as it should be trailing away from the sun.  (Frustratingly many people posting pictures and sketches on the web fail to indicate the cardinal directions on their image, so I can't confirm where the tail should be headed!)  I needed to tap / move the scope to see it.  It actually became more difficult to see -- it was apparent at first glance but after a few minutes I struggled to see it.  Exceedingly faint, if there at all.

Using 113x without the filter the nucleus was easily seen, almost stellar, and really popped out with averted vision.  Even with the higher magnification the coma seemed not to have lost any of its size.  Adding the comet filter confirmed my impression of the tail direction.

I then turned to Jupiter, which disappointingly could not bear magnification at all -- seeing had suddenly turned quite bad.  At the start of the session I was getting airy disks, but now everything was bloated.  No Galilean moon events happening, so I turned to Mars, which was a nice ruddy color, and I detected a hint of dark patches and lighter pole.  Venus was much lower in the sky than a couple weeks ago when I first saw the comet.  I looked at some favorite double stars (Zeta Leonis, Cor Caroli, Delta Corvi), but all were bloated and only hinted at the color and beauty of these pairs. 

As it neared 6:00 am the sounds of the highway grew louder, I could hear the engine roar of the garbage truck as it started its round through the neighborhood, and the sky was beginning to brighten.  I had a look at the moon awhile, but even at 113x the image was turbulent.  I started to think how good it would be to have some coffee, so packed up and came inside.

I hope to have more chances at this comet in the coming weeks under more favorable skies.

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