|
Posted by Prai Jei on March 17, 2007, 2:29 pm
Please log in for more thread options
baalke@earthlink.net (or somebody else of the same name) wrote thusly in
> The purpose of the experiment was to measure the 'dark current' of
> STEREO-B's CCD detectors. The idea is familiar to amateur astronomers:
> Point your telescope at something black and see how much 'dark
> current'
> trickles out of the CCD. Later, when real astrophotography is taking
> place, the dark current is subtracted to improve the image.
>
> In this case, the Moon served as a black calibration disk backlit by
> the
> sun. "The observation was no accident," she says. Mission controllers
> arranged the alignment with a small tweak to STEREO-B's orbit last
> December and engineers have been waiting for the dark current data
> ever
> since.
et ibidem infra:
> The Moon seems small because of STEREO-B's location. The spacecraft
> circles the sun in an Earth-like orbit, but it lags behind Earth by
> one
> million miles. This means STEREO-B is 4.4 times further from the Moon
> than we are, and so the Moon looks 4.4 times smaller.
If the moon's disc were so much smaller than that of the sun (hence the
event is described as a transit rather than an eclipse) there would be most
of the sun's disc still showing. How would that allow one to measure the
"dark current"?
--
He hadde not leyser for to loke after who is his freend & who is his fo.
- The Cloud of Unknowing (anon, 14th century)
Interchange the alphabetic letter groups to reply
| 
XML Sitemap