NB: Many of the comments quoted here have since been deleted by straydog, ostensibly to tidy up his channel comments section, and to remove things that aren’t actually correct. It does have the added bonus, for him, of hiding all the fuck-
This topic that has created a lot of comment as he backs and forths with the occasional person who isn’t actually him in his comments section.
It’s based on a throwaway comment made by Gene Cernan in this video:
“[Earth] was very close to the horizon on Apollo 17 and that was unique for us we didn't have to look up like most of the other flights from most of the other Landing sites were to look at the Earth I mean I just glance over my shoulder and there's the Earth.”
Now, anyone who knows anything about Gene Cernan is he loves a good yarn, and his tales have been told so often they can take on a life of their own. Stray takes issue with that “close to the horizon” quote, partly because his own subjective interpretation of “close” doesn’t match with what he understands to be available in the Apollo photographic record.
Initially he seems content with the figure recorded in Apollo documentation, like this table.
There’s very obviously some filling in of missing sky. Still sceptical? Let’s take one of the photos taken at the flag showing Earth and superimpose it on the south massif, using the same points on the landscape to get the alignment correct.
Fancy software wasn’t around when the Apollo missions were, so these panoramas were hand assembled. Here it is on the ALSJ site:
This version is from the Geology report, a physical copy of which I own.
The Earth is very obviously not in the field of view of the camera.
Stray tries to make a big deal about the that field of view, claiming that the Hasselblad 60mm lens used only has a 47 degree view, but seems to forget that a substantial amount of that field here is made up of the ground. Even he says it’s not reliable:
“You also can’t derive altitude angles reliably from a wide-
He also says that
“the photographer had to either bend down, or get on his knees”
to get the photos. Which is exactly what they did (see below).
It’s worth reminding everyone here that initially he was happy that Earth was correctly placed!
Earth is exactly where it should be. 45 degrees above the actual horizon.
Now that he’s edited all his previous comments, it’s started to become increasingly difficult to edit this document without it getting overly complicated. With that in mind I’ll add new things at the end.
One of those new things he’s added is that his critics are configuring the Virtual Moon Atlas software incorrectly when deriving values of libration. He’s insisting that people are configuring for the lunar centre rather than surface (topocentric) values. Yet again, he’s displaying that he’s never been anywhere near the software. The VMA does not place itself on the moon. It is specific to views of the moon from Earth. Yes it does have a topocentric option, and this will affect the libration values, but he hasn’t demonstrated that people are doing it incorrectly.
Setting the VMA to show how the moon appeared on any of the dates during the Apollo 17 EVAs gives you libration values of -
Hilariously, he mistakes the sun’s altitude for the Earth, claiming a huge change in altitude over the course of the EVA. His main objection comes from the fact that his idea of close to the horizon differs. In fact at one point he states quite specifically that the Earth is exactly where it should be in the Apollo photos.
Here are some typical views from magazine 134 and 137.
Things take a turn when he tries to do maths. Or at least get a range of AI packages to do the maths for him. As far as he is concerned, his new figure for where Earth should be is around 70 degrees above the horizon, based on the simple premise that the Taurus-
By changing the projection to ‘Lunar Globe’, it’s possible to set your location to a specific spot and rotate around it. You also have the option of entering a start date, and displaying the Earth. Here I’ve set the start date to coincide with Apollo 17, and I’m rotating around a point in the Taurus-
It does not show the position of the Earth above the South Massif, nor does it ever “confirm the high elevation”.
Prove me wrong.
Now for NASA/JPL ephemeris figures, which he calls “the gold standard”. You need to go to this website and type in the relevant values.
Which gives you:
The column we need is the ‘Elev’ column, which reads from a minimum of 44.02 degrees to a maximum of 45.28 degrees. The gold standard fundamentally contradicts straydog’s claims.
Now for Stellarium. Stray insists that Stellarium shows his 70 degrees figure, and that the reason nobody else gets that value is because we’re all doing it wrong. Here’s how we all, apparently, have been doing it wrong:
“This [45 degrees] is impossible, because Stellarium itself uses the JPL DE ephemerides, the Moon’s rotation matrix, and topocentric geometry. When set correctly, it ALWAYS reproduces the same result as SPICE within <0.3°.
Stellarium has two Moon observers:
Center of Moon (wrong!)
Topocentric surface point (correct)
Your troll’s friend 100% used the center of the Moon, which drops Earth altitude by ~25°.”
Apparently, we should also turn libration off.
Well, for a start I have yet to find anywhere in Stellarium’s set up that allows libration to be turned off. He gets confused a lot about libration (or at least, his AI is inconsistent. In one post he’ll say it’s insignificant (usually when using a strawman argument to claim that ths is why his opponents claim a 15 degree change in elevation over the mission -
“Earth’s apparent position shifts by several degrees due to lunar libration”
In his world it’s simultaneously hugely important and not important at all.
As an explanation as to why Earth is higher than his opponents are claiming.
He also seems to be claiming that adding libration “double counts” Earth’s movement in the sky, because lunar longitude apparently relates to the sub-
“The 45° result is wrong because it double-
It’s not difficult to get confused here. While some scientists are arguing to fix the meridian on a physical feature, the current accepted consensus is to use the ‘mean sub-
As you can see, there’s no real variation at all, certainly not the 25 degrees stray thinks should be happening because we’re all so incompetent at using it, and it’s nothing to do with him having never used it at all and relying on force-
The other thing you’ll notice there is that there isn’t a lunar surface visible. You can change Stellarium’s landscape to match where it say you’re viewing, and stray has become convinced that this landscape is what the software is somehow measuring. He’s at least moved on from claiming that the 45 degree figure is because it was measuring from orbit.
It is not the landscape.
The landscape files for Stellarium use a simple ‘.png’ file, referenced in 3D space by other software and imported into the program. The software absolutely does not reference that imagery when calculating the various coordinates available to you as a user. Here’s the same scene presented with and without the landscape.
Absolutely no difference whatsoever to the figures it generates. Zero. Because it’s looking at a set zero datum that has nothing to do with whichever arbitrary choice of landscape you want. You might notice the grid superimposed on the view.
You might also notice which lines intersect Earth. It’s not 70 degrees. If you’re really observant you’ll spot that the first visible line on the Apollo landscape isn’t zero -
Here they are superimposed.
He demands people post screenshots of the settings used and the figures for Earth -
Speaking of the view, his next big “a-
Oh no! You can’t see Earth, it must be fake!
It doesn’t seem to occur to him that the black sky might have been filled in by the Moonpans website in creating the panorama. In this part of the Moonpans site, the construction is explained:
Add to that the natural wobble of the moon in relation to Earth (libration) and there’s a little more variation. He knows that exists, but all he manages to do is subtract libration values from his false 70 degrees figure to produce answers that are still incorrect.
At one point he claims the Apollo lunar Surface Journal makes references to a figure of 60-
Another claim he had to backtrack from (or pretend that it was a trap!) was that the elevation of Earth wasn’t ever mentioned, and certainly not 45 degrees. The obvious response to that is to quote this from the transcript:
“142:44:42 Parker: You might check the low-
…
142:45:00 Cernan: Okay. Yeah, we are at 45 degrees (low-
Stray’s response to that is to go into a long discussion about how the earth elevation is actually just antenna elevations, nothing to do with Earth. Except he seems to think it relates to the High Gain Antenna (HGA), not the Low Gain Antenna (LGA) referenced by Cernan:
“The HGA elevation angle is a mechanical angle internal to the antenna mount, referenced to the rover/antenna assembly, not to the lunar horizon.”
“As we discussed before, the LRV high-
He also references a specific document that deals with radiation management, quoting text that does not appear any within it. He does at least mention this document as a source, which does have relevant information in it. When combined with this document we can get a proper picture. Dealing with the antenna he thinks we’re talking about, the HGA is the large umbrella like piece of equipment that needs to be pointed pretty precisely at Earth in order to work.
The HGA is aligned by first getting a rough alignment by eye, then using a combination of a boresight and a meter indicating S-
As far as the LGA is concerned, that does have markings on it, but the documentation says this:
“The antenna elevation (lunar surface to earth) is set by unlocking the elevation adjustment lock, tilting the antenna at pivot point to desired elevation angle, and re-
The bold emphasis is mine, but the reference is specific. What stray is trying to imply is that the rover is on a slope, and the 45 degree angle is what’s needed to compensate for that slope. Luckily we have a couple of good photos of the LRV in place at Station 2.
The HGA antenna here is pointing at Earth, which is out of shot. In order for an Earth 70 degrees above horizontal to be reading as 45 degrees, the rover should be on a a 25 degree slope. That’s steeper than the actual South Massif.
Here’s something else the document he’s using contains (despite later claiming no documents at the ALSJ do this, and his pet AI package was similarly unable to find) -
He now insists that the ALSJ says it’s 54 degrees. It does not.
He later claims that these elevations show Earth elevation
“In the LM reference frame”
And not above the true lunar horizon. That’s a) meaningless, and b) simply not true -
Stray makes a big deal about my modifying the landscape. Apparently that’s a “red flag”, and I have “admitted” changing it. Conspiracy nuts love to say you’ve “admitted” something. It makes it sound like they forced it out of you at gunpoint and it’s a victory for them. What he means by “admitted” here is that I found a problem with Stellarium’s landscape, fixed it, told everyone I’d fixed it, and gave them the files so they could use it themselves. My making of that change made not one iota of difference to the elevation figures, it just made the view look more correct, as you can see below. The top line is the two png files used by Stellarium, with the original configuration on the left. The latitude/longitude figures are give from the landscape.ini file.
And here’s how that translates into the view using exactly the same date and time (13/12/72, 07:00).
Earth is now more correctly positioned, but the values displayed on the left are unchanged. Stray’s claim that Stellarium is somehow mistakenly reading the top of the south massif isn’t helped by the original positioning of Earth being nowhere near it!
There’s a lot of discussion about Stellarium, and how everyone else is using it wrong and if only you use it properly there you’ll get the figures he wants. Not once has he ever done that. Nowhere does he do what I’ve done above: provide an illustration of the numbers. It’s “trust me bro” -
He claims that users aren’t turning off atmospheric refraction for the moon, and that his has a result. There’s no such setting. There is this, but hey guess what, it has no impact on the result.
Turn the atmosphere on for the moon, and the sky turns blue, but the Earth elevation stays the same.
He expands on the “LM reference frame” arguments where he concedes that, despite arguing until he was blue in the face that it absolutely had to be 70 degrees, it should actually only be 54 degrees. Or at least he gets Grok to admit it on his behalf.
Groks mistake, apparently, was to
“ LM tilt antenna mounting offsets and body-
This is just word salad, with a dressing of bullshit. It’s meaningless. The initial figures in the press release quoted above were pre-
He even says this in relation to those values:
“Earth is rising slightly each EVA. .. That matches: LM attitude changes and libration trend, NOT a fixed surface horizon.”
Again, wtf? Yes, Earth is rising slightly over the course of Apollo 17’s stay exactly because of libration trend, but attitude changes? The LM is moving? Maybe read your AI output to see if it makes any kind of sense before posting. He suggests that it’s actually the lunar modules “6-
By far the longest exchanges relate to his insistence that popular astronomy software Stellarium, NASA’s own website where lunar ephemeris can be calculated, and even the Lunar Reconnaissance Orbiter website vindicate his stance.
Let’s deal with that one first. Here’s what he has to say:
“LROC QuickMap (Arizona State University): This tool, based on Lunar Reconnaissance Orbiter data, shows Earth high in the sky (~70°) when viewed from the Apollo 17 site at EVA times.”
And
“LROC Quick Map: This tool uses actual Lunar Reconnaissance Orbiter topographic data. If you use the "Sun/Earth" tool on Quick Map at the Apollo 17 site, it confirms the high elevation.”
OK then. This is the only possible thing he can mean at the quickmap.
It is not always the exact centre of the moon’s face relative to Earth. The coordinates of Taurus-
As for using the topocentric surface, it’s enabled by default in my version. What it does is ensure that you’re getting azimuths and altitudes relative to your position, rather than the point measured from the moon’s gravitational centre. In reality, turning off that figure does very little to the Earth’s altitude -
Again, that’s the moon’s movement as viewed from Earth, but it does generate values that you can use to calculate where the Earth will appear, as demonstrated very well here using VMA figures.
Stray seems to have issued his final edict on the topic (thank fuck, I’m sick of dealing with it), and makes a number of critiques of jenny’s excellent video. He actually says this about JPL’s calculations:
1. The “Houston Observer” Error (~01:45)
In your video, you set the JPL Horizons Observer Location to Houston, Texas.
This is a fundamental mistake.
When you choose Houston, Horizons returns Earth-
To compute Earth’s altitude from the lunar surface, the observer must be set to the Apollo 17 landing site (20.19°N, 30.77°E).
This is despite the video literally showing Apollo 17’s coordinates, just like my use of the same site.
He seems to be fundamentally incapable of double checking his facts, just like when he says:
2. The Stellarium “Landscape” Misinterpretation (~04:30)
You show Stellarium displaying a 45° Earth elevation.
Stellarium’s “Moon” landscapes often include generic mountains that do not match the actual Taurus–Littrow topography. If you measure the angle from a mountain peak instead of the true astronomical horizon, you will naturally get a lower value.
The Earth’s true altitude — its angle relative to the local vertical — remains 53.4°, regardless of what terrain blocks the view.
This is despite Jenny’s video (and my explanations above) clearly demonstrating that Stellarium doesn’t look at anything in the landscape that can affect the results. He also insists that if you put in the Apollo 17 landing site in Stellarium you get the values he’s claiming are correct, when you absolutely, definitely, do not, just like his other claim that putting a value compensating for Apollo 17’s delayed launch affects the figures. It does not, at least, not in the way he hopes -
The simple fact is that the position of Earth in the lunar sky varies between 44 and 62 degrees over the course of a year (at least in 1972). Feel free to check. It doesn’t matter how much AI you fire at it, celestial mechanics is immune to your promptings, and at the time of Apollo 17 it was at around 45 degrees.
You’d think that would be the end of it, but no, stray continues to insist that black is white and that 2+2=54.
He criticises the use of pre-
“A pre-
And insists, on more than one occasion, that the post-
Nowhere on that page, or indeed any other page, is Earth’s elevation given as 54 degrees. In fact, as best I can tell, the only references to elevation at all relate to the sun or to landscape. Earth’s elevation isn’t mentioned. Now either stray knows this and he’s lying, or he’s never read the document and he’s lying. Either way, it’s just not true. His cinfusion is illustrated by this:
NASA SP-
“The Earth was at an elevation of approximately 54° at the landing site.”
Where he’s now saying the science report is a pre-
I’ve already shown the results of an ephemeris calculation above that shows JPL horizons calculating Earth’s elevation correctly, but stray gives step by step instructions. So let’s see if we can replicate his values.
Seems simple enough.
Or is it?
So no, you don’t click on “web interface”, you click on the “App” tab. This may seem a trivial to pick on, but this and many errors like it indicate he’s eitehr not on the same page he’s pointing us to, or he’s never been to it at all.
Next we have his instruction (left) with reality (right):
Searching ‘moon[301] as he instructs finds nothing. In fact searching ‘moon’ doesn’t help, it finds locations on Earth called ‘moon (below left). To actually get to Apollo 17’s site, you need to do as the page instructs and look for apollo@301, and from there you can pick lunar locations (below right).
So the first two basic steps are incorrect, how about step 3?
We’ll leave aside the fact that there isn’t a ‘continue button. The EVA midpoint is more or less correct.
Step 4 -
As you can see, the Observer settings are done in step one of the whole process, not within the table settings. There is no option to select ‘IAU_MOON as a reference frame, just ICRF (International Celestial Reference System) which has a coordinate system in the barycentre of the solar system, or FK4/B1950.0, an older version of the same sort of celestial reference system. I’m not even going to pretend to understand how they’re calculated or what the difference is, we’ll just go with the default of ICRF, seeing as stray’s option just isn’t there. You can choose IAU_MOON as a coordinate system in JPL’s SPICE packages, but it isn’t available here. This document suggests it isn’t a suitable reference frame for high accuracy lunar orientation, but again, the technicalities are beyond me. It’s moot: the option isn’t where stray says it is.
As for ‘Output quantities’, there’s no ‘edit quantities’ option. You do get to choose from the list shown on the right. His values of “sub-
All that gives you is this:
And a button that says “generate ephemeris”, which we can click. But oh no! You get an error:
So you cant follow step 2 as he’s given it. Let’s put EVA start and end times in for EVA 1 instead.
There’s a large amount of information presented in the results that aren’t relevant, so we’ll stick to this bit that is:
The really important parts here are the Azi__(a_app)__Elev values of 240.710074 and 45.112800.
The values are explained below the table:
Azi____(a-
Airless apparent azimuth and elevation of target center. Compensated for light-
In other words, where is the Earth as far as the observer is concerned. It’s 45 degrees above the horizon.
The Observer sub-
Apparent planetodetic longitude and latitude of the center of the target disc (Earth) seen by the OBSERVER at print-
In other words, it’s where the centre of the Earth is, as seen by the observer form the moon. It has nothing to do with the position of the Earth in the lunar sky, other than the fact that it’s obviously influenced by lunar libration. So when he goes into step 6:
He’s using entirely the wrong values. Unless, of course, the ObsSub Lon and ObsSubLat are not the values he’s talking about, in which case when he says “you will see output lines like”, you need to tell us where to find the options to show us -
His next series of calculations involve computing values from the coordinates of the Apollo 17 LM with values we haven’t seen this web page produce. Similarly, we get no values presented in any of the stages of calculation he presents us with in a terribly formatted set of equations. He merely produced an answer at the end that says “if we’ve calculated properly” we should get the values he insists are correct.
Well, we did calculate properly, and the values he produces are incorrect, and the sources he claims show the figures he quotes do no such thing. The value of 54 degrees is certainly reasonable value for the median elevation, given that the range is between 44 and 62 degrees, but he obviously isn’t accounting for libration, no matter how much his pet AI says he is.
Let’s summarise where we are:
Claims that mission transcripts mention Earth at 54 degrees: false
Claims that pre-
Claims that post-
Claims that Stellarium shows Earth at 54 degrees: false
Claims that Stellarium has been incorrectly configured: false
Claims that JPL Horizons shows 54 degrees: false
Claims that JPL Horizons has been incorrectly configured: false
To be continued…