The Apollo Command Module had the Scanning Telescope for navigating, "Apollo astronaut located a specific star using a single-power, wide-field telescope."

I'm not concerned whether it could significantly magnify the appearance of the disc of the planets, just could they simply move the position of the telescope to view the planets or was it fixed to view the specific star for navigation purposes only.


1 Answer 1


The scanning telescope had a 60 degree field of view and 1X magnification, so planets within that field of view would have been visible.

The scanning telescope could be moved +/- 270 degrees in one axis and -5 to +50 degrees in its other axis. It was normally moved simultaneously with the moveable line of sight of the sextant. The large degree of freedom is around an axis normal to the surface of the command module, the other is perpendicular to that. The manuals call the axes "shaft" and "trunnion"; I would call them "pan" and "tilt".

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Larger movements would require maneuvering the vehicle.

Note, however this comment by Collins about the telescope.

As a general comment, I've found that the telescope was a very poor optical instrument in that it required long, long periods of dark adaptation before any star patterns were visible.

And similar comments by Armstrong

I think we already covered that by saying that with the LM on in the daylight the telescope is nearly useless and you have to rely on the sextant. Now, we never went into that mode that Apollo 10 discovered of pointing the plus X axis at the sun. We never had an occasion or need to do that. Therefore, we can't comment on it. Just staying regular PTC attitude, normal to the sunline, the telescope was just about useless.

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    $\begingroup$ I seem to recall someone describing it as "the most expensive 1x telescope ever made" or something? $\endgroup$ Feb 22, 2020 at 2:05
  • $\begingroup$ If "The scanning telescope could be moved +/- 270 degrees in one axis..." is correct then I'm gonna ask a follow-up. That's 540 degrees! Actually even if it's only "through a range of 270 degrees" I'll still ask how that's possible $\endgroup$
    – uhoh
    Feb 22, 2020 at 2:56
  • $\begingroup$ @uhoh direct quote from the 2nd reference. $\endgroup$ Feb 22, 2020 at 3:01
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    $\begingroup$ I've asked (and then deleted) [How did the Apollo spacecraft's scanning telescope move 540 (+/- 270) degrees? Why did it need to? I'll have a closer look now that you've edited, maybe it's all explained here. Thanks! $\endgroup$
    – uhoh
    Feb 22, 2020 at 3:11
  • $\begingroup$ Okay, got it. Rather than a "scanning 1X telescope" I would have called this a "hemispherical periscope" $\endgroup$
    – uhoh
    Feb 22, 2020 at 3:23

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