Apollo 9 hatch

[Dalhousie]

Morning all

I know this has been answered before, but I can't find them. 

There have been a proliferation of claims in my social media feed recently that the famous Apollo 9 EVA image because the CM hatch sides look straight when it is supposed to close on the curving hull,, as below.

Now, the closest I have been to a CM hatch is to Apollo 17 at JSC, and the hatch is clearly curved to match the hull, as seen on multiple visits.

Explanations please, with thanks!

[Ranb]

Perhaps you can ask the claimants to provide a photo of the hatch side view to show if it is straight or curved?

[Dalhousie]

Perhaps you can ask the claimants to provide a photo of the hatch side view to show if it is straight or curved?

The difficulty is the  previously attached A9 image appears to be straight on three orthogonal sides, when it should be curved on the fore and aft edges at least.

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

[Zakalwe]

There have been a proliferation of claims in my social media feed recently that the famous Apollo 9 EVA image because the CM hatch sides look straight when it is supposed to close on the curving hull,, as below.

Hoax proponents unable to understand perspective in photos. More shocking news at 10!

/s

[Miss Vocalcord]

Perhaps you can ask the claimants to provide a photo of the hatch side view to show if it is straight or curved?

The difficulty is the  previously attached A9 image appears to be straight on three orthogonal sides, when it should be curved on the fore and aft edges at least.

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

It is clearly the other way around; the hull is straight and the hatch is curved as clearly can be seen from this picture:

Or it could be perspective....

[Jason Thompson]

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

It also shows one side to be noticeably longer than the other. I see no reason to bend over backwards to provide a detailed geometric and photogrammetric explanation of a simple effect like perspective. If those people think it's fake because it looks flat in a photo, disregarding the effects of perspective and lens distortion, ask them why on Earth (or the Moon) NASA would even make a flat hatch, never mind stick it on the side of a curved spacecraft.

[Dalhousie]

Perhaps you can ask the claimants to provide a photo of the hatch side view to show if it is straight or curved?

The difficulty is the  previously attached A9 image appears to be straight on three orthogonal sides, when it should be curved on the fore and aft edges at least.

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

It is clearly the other way around; the hull is straight and the hatch is curved as clearly can be seen from this picture:

Or it could be perspective....

That's a nice photo, and it could be useful, do you have a link to it?

Although when measured I can show myself that the fore end of the hatch opening is curved, along with the top of CM.

[Dalhousie]

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

It also shows one side to be noticeably longer than the other. I see no reason to bend over backwards to provide a detailed geometric and photogrammetric explanation of a simple effect like perspective. If those people think it's fake because it looks flat in a photo, disregarding the effects of perspective and lens distortion, ask them why on Earth (or the Moon) NASA would even make a flat hatch, never mind stick it on the side of a curved spacecraft.

I understand perspective, you understand perspective. We both understand that the hatch is curved.  I quite would prefer to have to hand something a bit more robust than simply "because I say so".

[Miss Vocalcord]

Perhaps you can ask the claimants to provide a photo of the hatch side view to show if it is straight or curved?

The difficulty is the  previously attached A9 image appears to be straight on three orthogonal sides, when it should be curved on the fore and aft edges at least.

The image below appears to show straight edges on four sides, fore and aft, as well as the sides.  The curve of the hull where the hatch fits is clearly visible.

It is clearly the other way around; the hull is straight and the hatch is curved as clearly can be seen from this picture:

Or it could be perspective....

That's a nice photo, and it could be useful, do you have a link to it?

Although when measured I can show myself that the fore end of the hatch opening is curved, along with the top of CM.

Sorry, I thought it would simply redirect to that site:
https://www.dreamstime.com/nasa-apollo-cm-command-module-hatch-detail-kennedy-space-center-here-close-up-photo-egress-kitty-hawk-image186591867

And yes on closer look it is curved, but I think it does show the quite good how perspective works
Here are a few other sites with the hatch opened which have different perspective views:

https://discover.hubpages.com/education/ApolloSpaceCapsules


https://www.aopa.org/news-and-media/all-news/2019/june/17/visit-all-the-space-race-capsules

[JayUtah]

Another factor to consider and to bear out in testing is lens distortion. The Zeiss Biogon lens, like many wide-angle lenses, does not provide a spherical projection. Instead it pushes distortion to the edges of the image in favor of preserving the angular relationships and reducing distortion in the center of the frame. This means that the closer a depicted object is to the edge of the frame, the more likely it is to be distorted in a non-uniform way.

I don't presently have a Biogon lens, but I can get one. Time permitting, I can test this hypothesis on models.

[Dalhousie]

Another factor to consider and to bear out in testing is lens distortion. The Zeiss Biogon lens, like many wide-angle lenses, does not provide a spherical projection. Instead it pushes distortion to the edges of the image in favor of preserving the angular relationships and reducing distortion in the center of the frame. This means that the closer a depicted object is to the edge of the frame, the more likely it is to be distorted in a non-uniform way.

I don't presently have a Biogon lens, but I can get one. Time permitting, I can test this hypothesis on models.

That would be great.

Do we have CM hatch photos from other missions?  I am thinking of the Apollo 15/16/17 deep space EVAs.

Cheers