# Apollo 11 Landing question. **URL:** \ **Category:** Factual Questions\ **Created:** [July 21, 2019, 12:01am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373 "2019-07-21T00:01:34Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Tempe\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tempe_jeff/32/7328_2.png) [@Tempe\_Jeff](https://boards.straightdope.com/u/Tempe_Jeff)\ **Post date:** [July 21, 2019, 12:01am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/1 "2019-07-21T00:01:34Z")
Regarding the Apollo 11 landing and subsequent moon walk; why didn’t they wait until the Full Moon for the landing? By the way, Full moon was on the 28th that month. Seems to me, it would have been easier to communicate and perhaps, see them with our larger telescopes on Earth. What’s the Straight Dope here? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [July 21, 2019, 12:12am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/2 "2019-07-21T00:12:29Z")
[Can you see objects left behind on the moon?](https://www.telescopesplus.com/blogs/helpful-information/18965572-can-you-see-objects-left-behind-on-the-moon) > [@](#): > > Unfortunately the answer to this question is no. Not even the most powerful telescopes ever made are able to see these objects. **The flag on the moon is 125cm (4 feet) long. You would require a telescope around 200 meters in diameter to see it.** The largest telescope now is the Keck Telescope in Hawaii at 10 meters in diameter. Even the Hubble Space telescope is only 2.4 meters in diameter. Resolving the lunar rover, which is 3.1 meters in length, would require a telescope 75 meters in diameter. So our backyard 6 inch and 8 inch telescopes are not even going to come close! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 21, 2019, 12:17am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/3 "2019-07-21T00:17:16Z")
Communication would probably have been easiest at half-moon, because then, neither party would “have the sun in their eyes”. Likewise, any sense in which “seeing them” might be meaningful. Of course, the only sense in which we could “see them” was the laser retroreflector, and that was left behind and used for many decades afterwards (and could still be used, if anyone on the Earth had the funding and the inclination to build and operate a sufficiently-powerful laser). ---
**Author:** ![Tempe\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tempe_jeff/32/7328_2.png) [@Tempe\_Jeff](https://boards.straightdope.com/u/Tempe_Jeff)\ **Post date:** [July 21, 2019, 12:22am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/4 "2019-07-21T00:22:26Z")
Radio interference? ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 21, 2019, 12:24am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/5 "2019-07-21T00:24:00Z")
From orbiting or visiting spacecraft I believe most if not all of the LM descent stages have been photographed. There’s a great one of the Apollo 11. I’ll look it up and post the NASA link. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 21, 2019, 12:40am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/6 "2019-07-21T00:40:45Z")
> [@Chronos](#): > > Communication would probably have been easiest at half-moon, because then, neither party would “have the sun in their eyes”. … The time of launch undoubtedly had months of planning for many more reasons, not the least of which was the railroad schedule, metaphorically speaking, established years and months ago since Gemini, as train after train left the station (ignoring the Kennedy-decade thing). Since you mention “sun in your eyes,” it certainly was an issue in the first coupling of a separately launched vehicle) and another manned vehicle, the goal (successful but a quickly aborted mission) of Gemini VIII, Neil Armstrong’s first trip above 50 miles, and his first (of two 🙂 ) as an astronaut. (Armstrong was the commander and his seatmate was was David Scott.) The timing of both launches, each timed relative to each other to the split second to achieve the optimum equal-plane orbits, was critically scheduled based on an additional constraint, based on the debriefing of the previous Gemini crews: “You can’t pick out the craft you"re supposed to dock with when the sun is in your eyes.” So they made sure that they changed the time of day for VIII, rather than the guidance routines. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [July 21, 2019, 12:52am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/7 "2019-07-21T00:52:35Z")
> [@Tempe\_Jeff](#): > > Seems to me, it would have been easier to communicate and perhaps, see them with our larger telescopes on Earth. What’s the Straight Dope here? **running coach** got ahead of me, so for a graphical explanation of why telescopes on earth (and even Hubble if it had been there then) could not had seen (and still they do not) the Apollo modules on the moon, please check the short video from Curious Droid for that item: [QUOTE] so… why can’t we see these from the earth, why can’t we train our best telescopes on to the moon’s surface and see them there exactly where we left them the best part of 50 years ago. Well, there a bit of a problem…. and that is that the moon is 384,000 kilometres or 238,000 miles away and the landers and all the other things left behind are just few meters across. To give you an Idea how difficult a problems that it is….. it’s like looking for an object the size of a coin from 1000 miles away or the equivalent from New York to Florida…. so you going to need a pretty serious telescope. [/QUOTE] > [@](#): > > The Hubble has a mirror which is 2.4 meters in diameter, that was the largest that could fit in to the Space Shuttle when it was placed in to orbit. This gives it a single pixel resolution in ultra violet light of about 43 meters across on the moon’s surface, anything smaller than 43 meters across will just be hidden in a single dot which cannot be resolved any further, in fact we need really 2 pixels or more to make out anything at all… ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 21, 2019, 1:06am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/8 "2019-07-21T01:06:22Z")
> [@Leo\_Bloom](#): > > From orbiting or visiting spacecraft I believe most if not all of the LM descent stages have been photographed. > > There’s a great one of the Apollo 11. I’ll look it up and post the NASA link. Photos of the descent stages of the LMs of Apollo missions and other NASA paraphernalia–hell, you can see the flag from Apollo 17!–are available at the [Lunar Reconnaissance Orbiter Camera site](http://lroc.sese.asu.edu/images); use the search term “Apollo” and have fun. ---
**Author:** ![Tempe\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tempe_jeff/32/7328_2.png) [@Tempe\_Jeff](https://boards.straightdope.com/u/Tempe_Jeff)\ **Post date:** [July 21, 2019, 2:01am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/9 "2019-07-21T02:01:56Z")
> [@Leo\_Bloom](#): > > Photos of the descent stages of the LMs of Apollo missions and other NASA paraphernalia–hell, you can see the flag from Apollo 17!–are available at the [Lunar Reconnaissance Orbiter Camera site](http://lroc.sese.asu.edu/images); use the search term “Apollo” and have fun. Those pictures are awesome. You need the sun low in the sky to make out any detail, for sure. Thanks for the link.🆒😃 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 21, 2019, 3:09am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/10 "2019-07-21T03:09:20Z")
> [@Tempe\_Jeff](#): > > Seems to me, it would have been easier to communicate… No, why would it be easier to communicate? The Moon is roughly the same distance regardless of phase, and from any given point on the ground (away from the poles), it rises and sets once a day. The Moon’s phase only affects what local time the Moon rises and sets. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [July 21, 2019, 3:29am UTC](https://boards.straightdope.com/t/apollo-11-landing-question/837373/11 "2019-07-21T03:29:48Z")
The launch time was chosen to ensure the sun angle at the landing site was optimal. In order to be able land you need to be able to see the terrain well, which mean shadows of a reasonable length. Full moon would mean close to overhead sun, and little to no shadows, which makes discerning the terrain almost impossible. Too low an angle and you have an impossible clutter. Then you have other navigation issues (sun in your eyes) and heat load issues. Heat load and temperatures are another biggie. The temperature range on the moon is extreme, and you want neither full sun nor full cold. You don’t want to be walking on a moon surface hot enough to boil your feet, or so cold it freezes your boots so they shatter. The lander needs to be able to reject heat as do the astronaut’s space suits, and the range of temperatures they can work in is limited. Overall there was only a limited happy sun angle, and that angle at the landing site was the determinant of launch date. Since the landing sites run across the moons face, the phase of the moon at launch varied by about a quarter between missions.