Hale-Bopp

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

A little while ago as Hale-Bopp was still aproaching us there was some
discussion on the possibilty of using its movement to get a stereo pair .
 I took a number of slides and prints but so far have just had my first
attempts on print film developed. Using a 135mm telephoto I obtained a
print pair on a 30 second exposure each , the seperation between them was
not precisely recorded but there was considerable movement between them
both horizontaly and verticaly due to the arcing of the comet. This
vertical movement I eliminated on mounting as much as possible for both the
comet and background stars which moved even more relatively as shown by
their streaking during exposure while the comet did not. There did seem to
be some stereo depth both between the comet and stars and within the stars
themselves but the odd thing was that some of the stars apppear in front of
the comet which is very wrong. The orbits of the comet Earth and rotation
of the Earth are all anticlockwise so the Earths orbit and even more so its
rotation would seem to subtract from that of the comet so that it appears
to move less than the stars. But why are only some stars in the foreground
? I had thought that perhaps it was because those lower nearer the pole
star would have less apparent movement and below it their direction even
reverses. But I have now sent it off in a folio to my next in list and he
phoned me to say that he had done a stereo of Hale-Bopp as well with
something like two hours seperation which he felt gave better depth than
mine. He also photocopied mine and found he could play around with the
pairs to elimminate the stars coming forward of the comet and felt that
this was caused by "Twist" in my mounting although I had not  been able to
do this when I originaly mounted them .
  Can any other members of the group shed some light on this particularily
the astronomers have other people had any success with stereos of
Hale-Bopp. P.J.Homer



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