Re: Sat track photo

Raoul Behrend (Raoul.Behrend@obs.unige.ch)
Fri, 24 Sep 1999 09:38:16 +0200 (MET DST)

Hi Alan and the others,

On 23-Sep-99 at 23:38, Alan Pickup (alan@wingar.demon.co.uk) wrote:
> Raoul Behrend <Raoul.Behrend@obs.unige.ch> writes
> >Very bad scan. But for me forget diffraction: the are no major stars on
> >trails, and the trails are very too long for optical systems.
> >
> >I suggest planes. Or One plane and 2 satellites.
> 
> On the contrary, the two clearest "satellite trails" pass over the two
> brightest stars in the nebula to better than 1 minute of arc and deviate
> from exactly N-S by less than 1 degree (possibly much less).
> 
> To explain further, let us get the orientation correct. We need to
> rotate the photo clockwise by ~110 degrees to align it with N at the
> top. The left hand of the two (now) vertical lines passes over the star
> Theta-2 Orionis while the right hand one passes over Theta-2 Orionis.
> Though the latter is a multiple star (the Trapezium), it would measure
> only 0.3 mm wide on the scale of the photo as it appears in my S&T.
> 
> The remaining trails are less sharp and distinct but E-W run at 90
> degrees to the above two trails, to an accuracy of a degree or so.
> Unfortunately, they appear to pass (only!) 2-4 arc minutes N of Theta-1
> and Theta-2. Despite this, I agree with Rob Matson that the "satellite
> crossroads" (as S&T calls it) is entirely an instrumental effect,
> probably diffraction. The stellar alignments and the exact N-S and E-W
> orientations are too coincidental to be otherwise.
> 
> Alan
> -- 
>  Alan Pickup | COSPAR 2707:  55d53m48.7s N  3d11m51.2s W   156m asl
>  Edinburgh   | Tel: +44 (0)131 477 9144     Fax: +44 (0)870 0520750
>  Scotland    | SatEvo page:   http://www.wingar.demon.co.uk/satevo/

I'm sorry to say that your arguments arn't valid:
- brigther stars haven't the the same (and also brigther) line patterns
- stars which make diffraction are at the intersection of "vertical" and
  "horizontal" lines. Due to the bad scan, we (more or less) clearly see
  two crosses.
  So, we have two major stars which must occupy two diagonally different
  location of the four intersections. None exist.
- The do patterns of this length, stars must be *very very* brigther then
  the stars which are "candidats".
- A diffraction pattern doesn't have nearly constant luminosity along the line.
  The real shape is obtained be Fourier transform of the telescope's apperture
  and is near the gaussian shape.

My conclusions are (including some remarks by some other persons):
- it can't be diffration patterns
- many people speak about things they never saw carefuly and studied
  accurately
- basical optical properties are not known of Mr Everybody.

And: a bad scan of a bad inkdoted-print is a bad starting point of discussion.
If the real author of this picture is "listening" this newsgroup: let you put a
good scan of the original somewhere on the net !

With my best regards, Raoul

-----

Observatoire de Genve
Raoul Behrend
CH-1290 Sauverny / Suisse

Raoul.Behrend@Obs.UniGe.CH
http://obswww.unige.ch/~behrend

"Herbe  Nicot? Herbe  nigaud!"