Tuesday, November 19, 2013

Catching ISON at Dawn

After a week of trying, Danielle and I finally got a glimpse of Comet C/2012 S1 (ISON) at dawn this morning. Over the weekend, we set up the tracking mount in the front yard since the trees obstruct the eastern horizon from the backyard observatory.  Every morning since then has been cloudy, and last night, with another overcast morning forecast, we took the mount down.  This morning at 5am, when Danielle got up briefly, she noticed that the sky was clear and woke me up.  We were able to find ISON in 8x42 binoculars (faint fuzzy), despite the nearly full moon which was just past zenith and the streetlight in front of our house. We could not spot the same comet 2 weeks ago in binoculars under dark skies.

We also got a camera/tripod shot but there was too much star trailing. Wishing the equatorial mount was still set up, we decided to quickly redeploy it, mount the camera and large lens, and do a rapid polar align.  We finally got everything working at about twilight and grabbed a couple dozen frames before it got too light to see anything.

This image is composed from a stack of 21 frames with separate processing of the coma and stars. The image is cropped down considerably.

Comet C/2012 S1 (ISON), Nov 19, 06:15 CST - Canon 60Da, 400mm, f5.6, ISO-800, 21 x 5sec.
This is a further crop of the image to center on the comet itself at full resolution.

Comet C/2012 S1 (ISON), Nov 19, 06:15 CST - Canon 60Da, 400mm, f5.6, ISO-800, 21 x 5sec.
What is interesting to me is that the level of detail is similar, or a bit less, than the images from 2 weeks ago. However, these are 5sec exposures and the previous ones were 3min exposures. Hopefully, the comet will survive perihelion on Thanksgiving and we will be able to take some more dramatic shots of the tail.

We also saw Comet C/2013 R1 (Lovejoy) in the binoculars. The coma was clearly larger than that of ISON. We did not have a chance to image that comet.

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