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In the video Brian Eno on Apollo at 08:20 there is Apollo-era movie footage of the Earth seen through the window of a spacecraft.

In addition to the primary, large and overexposed half-full Earth image there is a second, smaller (~1/3x) and dimmer but otherwise similar looking and similar color image of the Earth which moves more slowly than the primary as the hand-held camera moves.

What would be the likely cause of this second image/artifact, consistent with all of these characteristics and with the (likely high) quality of the photographic equipment sent to the Moon?

Brian Eno on Apollo

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The windows of both the LEM and the CM were flat, but both were at least two sheets of glass: the LEM windows were two, some of the CM windows were two & an outer pane to deal with heat during reentry. See this document. At least some of them were coated.

The images are almost certainly from either from 16mm movie cameras or from the Apollo TV cameras: they certainly are not video cameras in any sense we mean that now. I now think this were from the TV cameras.

The artifacts have undergone an even number of reflections and at least one was from a curved surface.

I think, therefore that the second images are lens front-element-window reflections: although it's possible they are internal reflections in the camera lens system, this seems unlikely.

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  • \$\begingroup\$ Thanks! This seems like the most likely scenario. fyi I've just asked What kind of camera was used to produce this Apollo-era footage of the Earth? to get a better handle on the camera. \$\endgroup\$
    – uhoh
    Jul 29, 2019 at 1:48
  • \$\begingroup\$ @uhoh: I had assumed the TV cameras were B/W: this is wrong, as there were colour ones. So it may have been TV footage. \$\endgroup\$
    – user82065
    Jul 29, 2019 at 8:48
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Best guess, it's shot through the LEM window & the window is double-glazed & also curved.

Regular household flat double glazing does this...

enter image description here

It's not difficult to extrapolate that to a curved double-glazed reflection.

Alternatively, a flat filter on the lens, reflecting off the curved front lens element. It's hard to tell from that brief snippet the full circumstances of the shot; though obviously done on video, at considerably lower resolutions that we are capable of today. A filter might better explain the rapidity of the reflection's movement relative to the main image... though at cost of my 'fabulous' shot through the double glazing ;)
Either way, internal reflection somewhere.

btw, that wasn't a keeper, I was just messing around, though I guess I could remove the reflection in post.

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  • \$\begingroup\$ Interesting, I'll give this some thought! Are there any examples of curved and double-glazed windows that produce reflections of objects at infinity 1/3 their angular size? or curved and double-glazed windows used in the Apollo program? \$\endgroup\$
    – uhoh
    Jul 28, 2019 at 9:01
  • \$\begingroup\$ It really doesn't take that much extrapolation & the actual sizing is unimportant. Two sheets of glass will cause reflection. Curved glass generates virtual images at other than their real size., convex, smaller; concave, larger. \$\endgroup\$
    – Tetsujin
    Jul 28, 2019 at 9:12
  • \$\begingroup\$ The size is quite important because it tends to constrain the radius of curvature of the proposed curved and double-glazed window. You are talking about a reflection off of a convex surface rapidly followed by a concave surface (or vice-versa) of nearly the same radius of curvature which will tend towards cancelling each other's impact on the magnification of the 2nd image. Until you can find an example, I'm not convinced this is a realistic scenario within the context and setting described. \$\endgroup\$
    – uhoh
    Jul 28, 2019 at 9:20
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    \$\begingroup\$ If the reflection were from the front of the lens to the rear of the window, then the size ratio between the primary image and the reflection would obviously be affected by the distance the camera/lens was from the window. Camera closer = larger reflection; camera further = smaller reflection. \$\endgroup\$
    – Michael C
    Jul 29, 2019 at 0:39
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    \$\begingroup\$ None of the LM windows are curved. \$\endgroup\$
    – Russell Borogove
    Jul 29, 2019 at 1:51
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The key to this is at 8:22 in the video, you can clearly see that the image of the earth as it comes in from the left side is partially outside the frame. The reflection is also cut off. Also, the movement of the reflection in relation to the earth appears to be too great to be a reflection in the just the window panes.

So my guess would be that reflection is internal to the camera lens/sensor, aka lens flare.

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  • \$\begingroup\$ I know what you mean. We're still trying to figure out exactly what kind of camera it is and if it's 1960's video rather than film, we'll have to figure out what they were calling a "sensor" back then. I can certainly imagine a pair of reflections; first off of the "sensor" and then off of the final surface of the lens back towards the sensor. Videos from these cameras on the moon show a lag between the three color channels, there may be dichroic splitters and three dedicated sensors as well. \$\endgroup\$
    – uhoh
    Jul 29, 2019 at 15:47
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    \$\begingroup\$ earlier 'video' cameras on Apollo were tube tv cameras, some extremely primitive. But they advanced very rapidly: en.wikipedia.org/wiki/Apollo_TV_camera \$\endgroup\$
    – cmason
    Jul 29, 2019 at 19:13

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