[AZ-Observing] Re: ISS This Morning: Single Frame
- From: Albert Barr <ajbarr@xxxxxx>
- To: "az-observing@xxxxxxxxxxxxx" <az-observing@xxxxxxxxxxxxx>
- Date: Wed, 02 Oct 2013 14:46:16 -0700
Excellent job. I tried once and failed.
> On Oct 2, 2013, at 2:38 PM, Paul Lind <pulind@xxxxx> wrote:
>
> Tom, Jenn,
>
> Fantastic image. Great teamwork. As I see it Jenn did the really hard part
> by perfectly tracking a fast moving object using only a Telrad. She gave Tom
> the easy job of pushing the shutter button.
>
>
> Paul
>
>
> ----- Original Message -----
> From: Tom Polakis <tpolakis@xxxxxxx>
> To: AZ-Observing@xxxxxxxxxxxxx
> Sent: Wed, 02 Oct 2013 12:07:36 -0400 (EDT)
> Subject: [AZ-Observing] ISS This Morning: Single Frame
>
> 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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