[AZ-Observing] Re: ISS This Morning: Single Frame
- From: Howard Anderson <handy13@xxxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 03 Oct 2013 11:09:11 -0700
Wonderful Tom!
Very difficult to get a moving object in the frame of a small video chip!
Truly amazing!
Thanks,
Howard
Tom Polakis wrote:
>The Space Station made a favorable flyby this morning, so I shot some video
>with the webcam setup. Jenn did the tracking through the Telrad, while I made
>adjustments at the laptop computer. First, some numbers that describe why
>this remains challenging.
>
>In order to get a decent image scale, you need several thousand millimeters of
>focal length. With a 10" and a Barlow effectively working at about 2.5x
>(3500mm f.l.), the ISS occupies over 200 pixels of the frame at close
>approach. The problem is that it's moving at over a degree per second. In
>order to keep image smear due to motion less than 2 arcseconds, the shutter
>speed has to be 1/2000 second. This means that even when the ISS is magnitude
>-3, it's pretty faint when it's imaged at f/14, and requires the gain to be
>turned up to 11.
>
>Now you may think that you're good at wielding a Telrad, but that 1/2-degree
>inner ring is gigantic when compared to the frame's field of view of only 3.5'
>by 2.6'. And it takes the ISS less than 1/15 second to cross the long axis of
>the camera frame.
>
>All of that is a disclaimer for the noise in this image, which was taken near
>close approach. For scale, there are eight pairs of solar panels, and those
>thin vertical gaps between the pairs are about 8 feet in width, which
>corresponds with about 1 arcsecond at the distance of 300 miles.
>
>http://www.pbase.com/polakis/image/152678525
>
>Tonight, I should be able to put together a time-lapse showing its changing
>orientation as it flew by. I promise that the message pointing to that image
>will contain far fewer numbers than this one.
>
>Tom
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