APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

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Expand view Topic review: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by johnnydeep » Sun Jul 30, 2023 12:56 pm

Chris Peterson wrote: ↑Sat Jul 29, 2023 9:35 pm
johnnydeep wrote: ↑Sat Jul 29, 2023 8:57 pm
Chris Peterson wrote: ↑Sat Jul 29, 2023 1:27 pm

Not exactly. What they do is provide a dimensional reference on the film, which gets mechanically distorted during processing and handling. So they provide a correction mechanism for calculating accurate angular measurements, but not absolute distance.
So the crosshairs are at the corners of squares (when the image was originally taken), and that's what enables any distortions to be corrected?
Maybe. The point is, they are at very precisely known positions (on a glass plate inside the camera, that the film is pushed up against). That they lie on a precise grid would make sense, but they don't need to.
Ah, got it.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Chris Peterson » Sat Jul 29, 2023 9:35 pm

johnnydeep wrote: ↑Sat Jul 29, 2023 8:57 pm
Chris Peterson wrote: ↑Sat Jul 29, 2023 1:27 pm
Rauf wrote: ↑Sat Jul 29, 2023 6:13 am I read somewhere that using those crosses on the picture, you can determine angular distance or sth? but how?
Not exactly. What they do is provide a dimensional reference on the film, which gets mechanically distorted during processing and handling. So they provide a correction mechanism for calculating accurate angular measurements, but not absolute distance.
So the crosshairs are at the corners of squares (when the image was originally taken), and that's what enables any distortions to be corrected?
Maybe. The point is, they are at very precisely known positions (on a glass plate inside the camera, that the film is pushed up against). That they lie on a precise grid would make sense, but they don't need to.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by johnnydeep » Sat Jul 29, 2023 8:57 pm

Chris Peterson wrote: ↑Sat Jul 29, 2023 1:27 pm
Rauf wrote: ↑Sat Jul 29, 2023 6:13 am I read somewhere that using those crosses on the picture, you can determine angular distance or sth? but how?
Not exactly. What they do is provide a dimensional reference on the film, which gets mechanically distorted during processing and handling. So they provide a correction mechanism for calculating accurate angular measurements, but not absolute distance.
So the crosshairs are at the corners of squares (when the image was originally taken), and that's what enables any distortions to be corrected?

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Chris Peterson » Sat Jul 29, 2023 8:04 pm

Guest wrote: ↑Sat Jul 29, 2023 7:49 pm It looks like there are two suns. I assume this is a photographic reflection of some sort. Or does the moon really have two suns?
Of course, the Sun isn't actually in this image at all, just lens flares from it.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Guest » Sat Jul 29, 2023 7:49 pm

It looks like there are two suns. I assume this is a photographic reflection of some sort. Or does the moon really have two suns?

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Chris Peterson » Sat Jul 29, 2023 2:21 pm

Brewz wrote: ↑Sat Jul 29, 2023 2:12 pm Generally not a conspiracy theorist, but I believe the USA flag has been added by external means.
In other words, you're a conspiracy theorist!

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Brewz » Sat Jul 29, 2023 2:12 pm

Generally not a conspiracy theorist, but I believe the USA flag has been added by external means.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Chris Peterson » Sat Jul 29, 2023 1:27 pm

Rauf wrote: ↑Sat Jul 29, 2023 6:13 am I read somewhere that using those crosses on the picture, you can determine angular distance or sth? but how?
Not exactly. What they do is provide a dimensional reference on the film, which gets mechanically distorted during processing and handling. So they provide a correction mechanism for calculating accurate angular measurements, but not absolute distance.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Chris Peterson » Sat Jul 29, 2023 1:22 pm

orin stepanek wrote: ↑Sat Jul 29, 2023 12:26 pm I remember my wife and I went to a sci-fi movie when they reported
landing on the moon! That was a big moment back in those days! I
could never understand why we quit pursuing lunar exploration after
that!
We didn't. But we quite correctly recognized that there's nothing we can do on the Moon that can't be done better by a robot than a man. A lesson that we are unfortunately ignoring now.

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by orin stepanek » Sat Jul 29, 2023 12:26 pm

AS11-40-5872HR1024.jpg
I remember my wife and I went to a sci-fi movie when they reported
landing on the moon! That was a big moment back in those days! I
could never understand why we quit pursuing lunar exploration after
that! :roll:
82868958_3413326812070702_8997963657715384320_n.jpg
Going for a ride on the moon :D

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by madtom1999 » Sat Jul 29, 2023 10:07 am

As a kid I my dad came home with some prints direct from the negatives from the moon and they were just amazing. He also had a glass phial with some supposedly moon rock in. He was a man of extreme views and I did wonder if he was just trying to encourage me into science and these things were just baubles to do so. Then the fiftieth anniversary of the landings had our near neighbour Prof Lionel Wilson on national radio, Sometimes you can actually hold a piece of the moon in your hand!

Re: APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by Rauf » Sat Jul 29, 2023 6:13 am

I read somewhere that using those crosses on the picture, you can determine angular distance or sth? but how?

APOD: Apollo 11: Catching Some Sun (2023 Jul 29)

by APOD Robot » Sat Jul 29, 2023 4:06 am

Image Apollo 11: Catching Some Sun

Explanation: Bright sunlight glints as long dark shadows mark this image of the surface of the Moon. It was taken fifty-four years ago, July 20, 1969, by Apollo 11 astronaut Neil Armstrong, the first to walk on the lunar surface. Pictured is the mission's lunar module, the Eagle, and spacesuited lunar module pilot Buzz Aldrin. Aldrin is unfurling a long sheet of foil also known as the Solar Wind Composition Experiment. Exposed facing the Sun, the foil trapped particles streaming outward in the solar wind, catching a sample of material from the Sun itself. Along with moon rocks and lunar soil samples, the solar wind collector was returned for analysis in earthbound laboratories.

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