Comet C/1999 S4 Linear
January 23rdA comet brightens as it races in on it's sunward journey.........this faint cometary object was discovered in September 1999 by the Lincoln Laboratory Near Earth Asteroid Research Telescope. This is my first image of this comet which is expected to become a bright comet by next July passing just 0.75 A.U. from the Earth.
June 26thThe observing window is still remarkably short as the comet rises into the morning sky with dawn breaking so early at this time of the year. It was picked up visually as a 9th magnitude fuzzy glow with a tail just becoming apparent. This is a 4x40 sec exposure with 50 cm f/4 and SX CCD.
July 8th1999 S4 is now a nice telescopic comet. Visually the tail appeared to be 15 arc minutes in length. CCD image revealed a condensed coma with a broad head of the coma extending about three arc minutes. A narrow spine now appears down the central part of the tail which extends westwards. The comet is now about 8th magnitde. This is a 10x20 sec exposure with 50 cm f/4 and SX CCD aligned and stacked using QMips32.
CCD images as above tend to show
the central condensation as oversaturated.
This image is just a 40 sec exposure
which has just been logarithmically
stretched and gives a more realistic
view of the visual appearance of the
comet.
July 11th
The moon was still in the sky when this
image was taken. A 40 sec exposure
was grabbed just before clouds rolled in.
Earlier imaging was hampered by a
power cut until the early hours. Some
dark sky observers are reporting a two
degree tail.
Twenty three hours later I captured this
8x20 sec exposure image. The narrow
ion tail is now appearing more
pronounced.
Applying a rotational gradient filter
helps identify faint cometary jets
July18th
Despite a full moon the comet was still easily visible through 50 cm f/4.
Tail was not so visible but central condensation had grown and
appeared at mag 7.5. Image below is a 4x20 sec exposure.
July 21st
Comet now showing increasing activity adjacent to the nucleus.
Rotational gradient filter now shows three "jets".
July 25thThe nuclear condensation has a very much elongated structure tonight as these images below show:
This is a 9 x 20 exposure with 50 cm f/4.
A linear stretch of the above image has saturated the nuclear detail, but shows that the comet now seems to have lost its prominent nuclear "hood" that was evident on image of July 21st.
A false colour rendition of the previous image shows the highly elongated nuclear structure.
Again applying a rotational gradient filter shows how the inner detail of the coma has radically changed over the course of the last four days. Compare this image with that of July 21st. Is the comet fragmenting? Watch this space.
July 28th Comet Linear Fragments
Skies have remained cloudy for the last few nights and I have been unable to observe, but astronomer Mark Kidger observing with the JKT on La Palma has confirmed that the comet is now breaking up. Full story can be seen at the Comet Linear website. Here is a comparison of my last two nights observations showing how the nucleus elongated, over a few days.
