Re: ISS Solar Transit

From: Debasis Sarkar via Seesat-l <>
Date: Thu, 29 May 2014 01:40:26 +0530
Hi Frank,
Thanks for your detail explanation. yes i agree, it is a possibility what
you said. There might have been an error in location and I got stuck with
that. I did not check coordinate of the location with GPS. What I did,
simply I went by the Calsky center line map. Chosen thbe location exactly
on centerline, and went to that position. If you have seen the location,
there was a small water stream touching a road where the center line is
crossing. I have places myself exactly there. But as you have said, there
might have been an error of 200/300 meters in Google map or Calsky map.
THus, i have got myself located at wrong place.
It is a learning for me. Now onward I shall only take the coordinate from
Calsky and find the location with GPS.

Thanks and regards-

Debasis Sarkar

On Wed, May 28, 2014 at 10:56 PM, via Seesat-l <> wrote:

> Hello Debasis Sarkar,
> You wrote:
> "despite being on centerline (Plus Minus 200 meters), I did not get ISS to
> run through the center of solar disc. Instead, I had it pass through a
> distance of at least 1/4 solar radii from the center of Sun."
> From your photos, I agree with your estimate: the path across the disk
> appears to be about 5 minutes of arc away from the center of the Sun. Given
> an altitude of 417 km, and 87 degrees high, almost straight up, this
> corresponds to a position offset on the ground of about 600 meters (that's
> 417km*5/3438). You say you believe your position was accurate to 200
> meters. A difference of 600 meters is only moderately outside that limit.
> Is it possible you were 600 meters off the center line? Did you get your
> lat/lon from some GPS-equipped device at the time of the solar transit? If
> your position was instead taken from mapped data, like Google Earth or
> similar, there's a possibility of an offset that large. You wondered about
> an offset due to altitude above sea level. Since the ISS was nearly
> straight up, there would be no significant difference. Of course a slightly
> "stale" TLE is also a possibility, but there were no orbital adjustments
> around the time of your transit so this seem!
>  s unlikely to me. Small errors in the prediction algorithms employed on
> the calsky site are also a possibility.
> Frank Reed
> Conanicut Island USA
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Received on Wed May 28 2014 - 15:19:27 UTC

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