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Incorrect in the sense that the sextant is of no use on the occasion of complete platform loss, which is indeed the special circumstance to which I have been explicitly referring.
.. he is talking about the scanning telescope, you know, the wide view one-power telescope used to identify constellations, this had lighting issues. the sextant is a narrow field 28 power scope, it did not have any lighting issues it was able to spot stars easily without being dark adapted.
Navigation during the Apollo missions was conducted almost entirely by radar from the ground accompanied by calculations from the ground computers with lesser help from the onboard computer. The sextant and the techniques for using it were seen as an almost useless backup system by the time the missions to the Moon actually flew.
The onboard star charts, together with a valid launch reference matrix in the computer, helped appreciably and permitted use of indicated attitudes (trunnion and shaft angles) to locate stars. The stars Rigel and Sirius were used for the platform orientation. Once the platform was aligned, the navigation sightings using auto optics were no problem.
The Apollo Guidance Computer's sense of platform IS its sense of stars. There is no difference. The Apollo Guidance computer knows the platform to be so aligned by virtue of how in "its mind" the stars are believed to be related to the ship. The computer sees the sip's attitude in terms of the geometry of the stars about it, and as such, when doing a P52, the computer draws on this sense of relationship, ship to surrounding stars if you will, and so then presents a star to the astronaut given this, the computer's sense of where the star should be given the computer's understanding of ship attitude/platform, at any given time.
Both Alan Shepard and Ken Mattingly by their own admissions were in possession of Apollo CM optical/computer/guidance/navigation equipment that did not allow for effective running of a P51 program. This, as stars in both cases could not be confidently sighted under the circumstance of platform loss.
Originally posted by decisively
My point stands and stands well irrespective of your views as regards my choice in its presentation
reply to post by DJW001
Both Alan Shepard and Ken Mattingly by their own admissions were in possession of Apollo CM optical/computer/guidance/navigation equipment that did not allow for effective running of a P51 program. This, as stars in both cases could not be confidently sighted under the circumstance of platform loss.
One may conclude that Apollo is frauulent as one must be able to sight stars under such circumstances with absolute acuuracy.edit on 15-5-2012 by decisively because: spelling
Originally posted by decisively
reply to post by choos
Why have the scanning scope ? Please professor lay it out here. What pray tell was its purpose ?