Fwd: ISS Solar Transit

From: Debasis Sarkar via Seesat-l <seesat-l_at_satobs.org>
Date: Wed, 28 May 2014 18:40:00 +0530
Hi Arnold,
Thanks for your response.
you are true, due to of its being at top head, altitude factor was not a
big one to play role in path shift.
I have got myself located based upon Google map. I have pointed out and
marked the location in Calsky Map. And then got muyself at the location.
the place is outskirt of a semi urban place with maize and paddy fields. It
was too easy and chance of my making any mistake in getting placed was too
low. My possible offset from the exact center line in east west should not
be more than 200 meters. But as visible in the image, the offset of the
pass from Solar center is of at least 1/2 Solar radii. As I understand with
a 6km wide visibility path in hand, we must go at least 1.5km off
perpendicularly from the center line to have this 1/2 solar radii shift in
pass path from center of sun. The location is within 100km from my own
place and it altitude is 40meters above MSL.
Regards-
Debasis Sarkar



On Wed, May 28, 2014 at 6:19 PM, Arnold Barmettler <barmettler_at_calsky.com>wrote:

> Dear Debasis
>
> the altitude does not have an effect here, because the sun was almost in
> the zenith. How accurate do you expect your coordinates to be? Are they
> from GPS or from Google Maps?
> CalSky takes the altitude from SRTM3, so it should be a quite good
> guess. Anyway, do you know what was the altitude of your observation site?
>
> Best regards
> Arnold Barmettler
>
> Am 28.05.2014 14:31, schrieb Debasis Sarkar via Seesat-l:
> > Thanks for your response. I have interpolated two images of ISS to show
> the
> > path I have got.
> >
> > Kevin, you are correct. That was the reason I had my camera firing at
> 5fps.
> > It helped me in getting two frames with ISS on Solar disc although I did
> > not have 100% of the disc in frame as I was using a APS-C format cam with
> > F2000mm. The shift of ISS from center of Sun is not along its path but in
> > perpendicular to that. And that happens only due to parallax. Moreover,
> as
> > mine was a  4928 x 3264 pixel panel. I did not want it to have a drift of
> > more than 1 pixel during the exposure. So used 1/3000 sec exposure.
> >
> > Leo, thanks for your response. you have mentioned a very important
> issue. I
> > have suffered twice earlier due to last minute orbital correction. But
> > here, in this case, I checked the predicted center line  around 65
> minutes
> > before the T Time. Interestingly, even after 4 hours of the exposure, I
> > found my location being shown as on center line by Calsky. By then, they
> > must have incorporated the actual TLE that remained applicable at the T
> > Time of my shooting.
> >
> > Could there be a reason - that the altitude of the place played a role?
> > Calsky, the altitude of the place considered by Calsky was incorrect as
> it
> > happens with many places in mapping softwares ?
> >
> > Thanks and regards-
> > Debasis Sarkar
> >
> > The frame with two ISS images on solar disc is here:
> >
> https://www.flickr.com/photos/sky-watchers-association-of-north-bengal-india/14103590419/
> >
> >
> > On Wed, May 28, 2014 at 3:07 PM, Kevin Fetter via Seesat-l <
> > seesat-l_at_satobs.org> wrote:
> >
> >> Looking up the info on the pass, it happened around 5:50:43 utc.
> >>
> >> At the time, the sun was very high in the sky, so when the iss passed
> >> across the sun, it was travelling at a good speed across the solar
> disc. So
> >> when you when to take the exposure, the iss had moved a good distance
> away
> >> from the centre of the solar disk. You would need to capture at very
> short
> >> exposure times, and get a few images during the transit,  to hope to
> catch
> >> the iss at the centre of the solar disc.
> >>
> >> They say the camera you have, can capture up to 6 frames per second, so
> >> set the camera to do that.
> >>
> >> Kevin
> >>
> >>
> >> --------------------------------------------
> >> On Wed, 5/28/14, Debasis Sarkar via Seesat-l <seesat-l_at_satobs.org>
> wrote:
> >>
> >>  Subject: ISS Solar Transit
> >>  To: seesat-l_at_satobs.org
> >>  Received: Wednesday, May 28, 2014, 2:34 AM
> >>
> >>  Hi Friends,
> >>
> >>  I am new in this list and thanks for allowing me to be
> >>  here.
> >>
> >>  I am sharing a picture of ISS transit that I have taken on
> >>  17th May 2014
> >>  from a location lat=26.101400 & lon=87.984298.
> >>
> >>
> >>
> https://www.flickr.com/photos/sky-watchers-association-of-north-bengal-india/14024037178/
> >>
> >>  The optics was Celestron SCT 8" with Nikon D7000 at Prime
> >>  Focus.
> >>  I have taken a Video too with Sky Watchers 120mm f/8
> >>  reflector fitted with
> >>  a HD Video cam.
> >>
> >>  Interestingly, 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.
> >>  Width of visibility path was 6km. I was following Calsky fro
> >>  the
> >>  prediction. Could you please enlighten me on what might have
> >>  gone wrong?
> >>
> >>  Thanks and regards-
> >>
> >>  Debasis Sarkar
> >>  _______________________________________________
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> >>
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Received on Wed May 28 2014 - 08:10:46 UTC

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