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There is no easy way to
shoot a speeding bright comet, as it moves up to several degrees
per day across the night sky. Here are two representations of
the same mornings data, in which the comet moved nearly a third
the way across my 3/4 degree wide field during the 45 minutes
I was exposing it. The comet is currently a very diffuse extended
object, about half a degree in size and beaming softly at 6th
magnitude. The strong green coloration is actually a cyan color,
from the ionized gas of cyanogen in the comets coma. You can
also see a bit of tail here, extending off to the right from
the core.
The image on the
left panel is the full field of view of the telescope onto the
ST10 chip. The comet was exposed for 45 minutes and the data
was combined using "Minimum" directly onto the nucleus
of the comet in the very first image. Thus this is the position
of the comet on the first frame, with extended exposures merged
onto its core. This shows a non moving comet on a stationary
star field.
The second image
is the same data, but by summing the comets nucleus of all the
frames to make a time exposure like image. This shows the stars
streaked as the comet whizzes by the star field. Unfortunately,
the stars colors are not retained well because the color data
was taken sequentially and leaves multi color beads in the stars.
A one shot color camera would remedy this! Also, the field is
half the size. Why? Because the comet moved nearly off the frame
during the exposures, so the amount of field around the registered
comets head diminished with exposure. So the comet appears twice
the size of the image on the left.
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