Re: PHOTO-3D digest 1200

[John Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Thu, 29 Feb 1996 12:14:24 -0600
>From: bobh@xxxxxxxxxxxxx  (Bob Howard)
>Subject: Re: PHOTO-3D digest 1200

>Re: Stereo Acuity. John B.
>A digest or two back was discussing astronomy and if there was any
>"stereo parallax" to a star? I think that you will find that this was
>Herschel's biggest disappointment, that the earth's orbit as a base
>was not enough to get a parallax on even the nearest star! Whether the
>Hubble telescope could do better I don't know..as it may lay in
>resolution of the CCD sensors???

The definitive position measurements at the moment are probably those
from the ESA satellite Hipparcos, which operated until ~mid-1993. It was
launched specifically to obtain very accurate position and velocity 
measurements of a large number of stars, and despite severe problems with
the orbital insertion, was able to do so. It measured the positions of
>100000 stars with an accuracy of 1-2 milli-arcseconds (~10-100 times as
good as previous measurements), and about a million stars with lesser
accuracy.

The resolution of HST may be in the same order of magnitude or so, but I
don't know how accurate its positioning is.

John R.


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