[meteorite-list] 2011 MD Animation

From: Richard Kowalski <damoclid_at_meteoritecentral.com>
Date: Tue, 28 Jun 2011 10:43:56 -0700 (PDT)
Message-ID: <1309283036.74576.YahooMailNeo_at_web113605.mail.gq1.yahoo.com>

Hi John.

What you are seeing are not "companions" but instead are imaging artifacts called "hot pixels". They are pixels that have a non linear response and are normal. Astronomical imagers usually use a technique called "Dark Frame Subtraction" to remove these hot pixels from the image. I imagine Yure had some reason why he didn't "apply the dark".

?Another technique to reduce hot pixels is to lower the temperature of the imaging chip that as the response of these pixels becomes more linear again as the chip gets colder. Many use a combination of both cooling and dark frames. Professional observatories cool our cameras so cold that we don't have these hot pixels and don't need to this step during image processing.

Hope this helps.

?

--
Richard Kowalski
Full Moon Photography
IMCA #1081
----- Original Message -----
From: John Hendry <pict at pict.co.uk>
To: Richard Kowalski <damoclid at yahoo.com>; meteorite list <meteorite-list at meteoritecentral.com>
Cc: 
Sent: Tuesday, June 28, 2011 8:04 AM
Subject: Re: [meteorite-list] 2011 MD Animation
I'm counting what appear to be 17 fainter companion objects in parallel
trajectories. Is that what I'm looking at or is it some sort of video
artefact? If they are companions can their size be determined
approximately from the relative brightness or by some other means?
Thanks,
John
On 28/06/2011 01:24, "Richard Kowalski" <damoclid at yahoo.com> wrote:
>I got a few positional images of this object with our 1.5-m (60") on Mt.
>Lemmon last night, but Jure Skvar? at the ?rni Vrh Observatory in
>Slovenia obtained one of the nicer time lapse animations of the asteroids
>motion against the background stars.
>
>
>He writes on his Youtube page:
>
>"The images for this animation were taken using a 60-cm telescope from
>the ?rni Vrh Observatory on the night of 26 July 2011.? Each exposure
>was of 15 seconds.? The telescope was tracking on the asteroid, changing
>the rate of tracking between exposures.? The entire sequence lasted
>about 4h40m, during which 635 exposures were made.? At the time the
>asteroid was less than 200000 km from Earth.? At the closest approach
>some 15 hours later the distance was about 20000 km."
>
>4 hours, 40 minutes of imaging the NEO until his dawn, compressed down to
>43 seconds. Enjoy
>
>
>http://www.youtube.com/watch?v=p-pv18xDWCY
> 
>
>--
>Richard Kowalski
>Full Moon Photography
>IMCA #1081
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Received on Tue 28 Jun 2011 01:43:56 PM PDT