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Comet 103P/Hartley 2

Dopo un lungo periodo di assenza, rieccomi di ritorno con una cosa un po' particolare. Lasciamo da parte per il momento le teorie di base dell'elaborazione di immagini digitali e vediamone un'applicazione pratica e in un certo meaning "advanced".
The opportunity I was given the unique opportunity to use images of a 2-meter diameter telescope located in Hawaii, the Faulkes Telescope North (or more briefly FTN), while the object of investigations is the recent passage close to the Earth of the comet 103P/Hartley 2.
Many ground-based telescopes are focused on these nights the comet also to give some support to the forthcoming mission Epoxi , a sort of extension of the old Deep Impact mission that has been so successful a few years ago with the close encounter ( collision with a pilot!) on comet Tempel 1.
A British observer, Nick Howes, whom I thank for the exquisite availability, is following with diligence and for several days this comet using remotely FTN: A typical result is that (just downloaded ;-)...):

010 -11-01T14: 25:48.510 UTC - 5 sec. Filter: Bessell-R

Although it seems at first sight, this is a small square of sky of only 4.9 'x4.9' and the scale of the CCD is very interesting: just 0.2785 arcsec / pixel. According to the ephemeris at the projected distance of the comet on that date, each pixel is only 29 km! (Seeing Hawaii permitting ...). These images allow me
to test the functioning of a "filter" special that I implemented as a plug-in program Astroart : I pompously called DBM or Coma Median Model.
The logic is very simple and explain in detail in a later post: to create an artificial coma, based at the photometry of the original image, and subtract the original image itself in order to highlight areas Internal different brightness areas and very close to the inner core that would normally be hidden from the diffuse glow of the coma. But notice the small talk and immediately see the results.

First it should be noted that the filter will be applied in a much smaller than the original image, an area that will be slightly less than 1'x1 ', as shown in the image below:


All images are correctly oriented, with North up and 'East left.

Here is the first processing:

First we notice that I had to use a false color representation for an optimal light intensity variations. Top left, as well as guidance also indicates the direction of the sun (the angle with respect to North). Bottom left white segment represents the image scale in terms of comet or how big they are 1000 km. But what is this picture? Kits in the direction (from bottom center right), we see the brightest part of the crown that extends to form the tail. But the most interesting thing is in the direction of sunlight (from the center top left) where there is obviously some sort of "puff" (we call "jet"?) With a PA (Position Angle) of about 50 degrees.
You wonder it was the original image? Here it is already cropped from the frame 1'x1 ': is the sum of 9 images taken by 10 seconds with the filter "SDSS-r":


And now, here in rapid succession the other four dates (13 -14-15 and 16 October) that I could develop:

36 if. Bessel V filter ... oops the "jet" has disappeared

125 sec. filter "SDSS-r" returns to the "jet" with a PA of 45 degrees about

65 sec. filter "SDSS-i": the "jet" now has a PA of about 90 °

5 sec. filter "SDSS-i". Unfortunately, the S / N ratio is negative but you feel the same appreciable the presence of the "jet" with a greater than 90 ° PA

the moment is everything. In the next post we'll see what else can we expect this comet and also how it's done (and apply) the filter MCM