What are these markings on the Apollo Command Module hatch window for?

There’s a company selling reproductions of the hatch window from the Apollo command module: here’s a link.

The window appears to have a rotatable bezel with some markings on it - 0° ROLL, 55°R/L, 90°R/L. What would the purpose of the rotating bezel and those markings have been? It doesn’t seem like the view out of the hatch window would have been of much help in flight, being above the astronaut’s heads while they were in the couches - and anything they saw would have been at about 90° to their direction of movement for reentry.

Something for in-orbit maneuvering? For telling how bad the seas are after splashdown?

For identifying how they are oriented in the water after splashdown, I’m guessing.

“Customers who bought this also purchased…”

Why not just name him?

One would assume for docking. The docking port is in the nose of the spacecraft.

The LM had three windows, one in the roof, needed to see the CM, and also with markings. The two main LM windows had markings that would be useful for landing.

There is this brilliant picture from Apollo 9 showing the intense attention during docking.

This pic also from Apollo 9 is rather nice of the window in the CM

Thats not a bad price for a picture frame. If I had an autographed Neil Armstrong picture I’d consider a frame like that. Thats actually a fair price for a machined and finished part of that nature.

To add to my reply above. Any window is going to provide a good view for some part of manoeuvring. There isn’t any useful sense of moving in the direction the spacecraft is pointing when in space. The only engine that accelerates the craft forward is the main engine, all the other thrusters are set up to provide six degrees of movement - translations and rotations. Which are all needed.

The windows for docking with the LM are inset into angled recesses in the side of the CM and face toward the pointy end of the CSM. There were also dedicated telescope/periscopes to help with the ‘forward’ view. This window faces ‘up’ and slightly ‘forward’ from the POV of the astronaut in the central couch.

The fact that there is a rotating bezel with a 0° line on it suggests that an astronaut was supposed to reference against some visual feature out the window (horizon?) and then note the roll angle of the CM against that reference. I recall that the CM had two stable flotation modes after splashdown - pointy end up and pointy end down - so there was a balloon that would inflate near the pointy end to flip the CM heat-shield-down in the water. I wonder if rough seas would be enough to flip the CM over if it rolled past a critical angle.

The RCS thrusters could accelerate the craft forward or backward. Docking with the LEM and extracting it would be impossible, otherwise.

The marks on the window were for after splashdown. If compressors or bags failed in the uprighting system, it was possible for the astronauts to stabilze the CM by shifting their weight around inside–getting off the couch and repositioning themselves.

I don’t believe this was a rotating bezel. The horizon marks only make sense in the position they’re at. If an astronaut looks up and sees the horizon across the 90 degree marks, this indicates they are on their side in an unstable position with a roll attitude of 90 degrees. Another 90 degrees of roll will either put the hatch in the water or facing the sky. Because the center of balance was off center, they’d have to position the roll attitude properly before attempting to pitch the CM into a Stable 2 position (by moving their weight forward) or Stable 1, by moving aft. This allowed them to use the COG of the CM to their advantage. This was only a backup method of stabilizing.

That’s my understanding, anyway. If they looked up and saw the horizon across the 0 Roll line, they were already in the Stable 1 or Stable 2 position, depending on what side of that 0 line was water and what side was sky.
If only water or only sky was visible, they are unstable and on their side. They should roll until a horizon is visibe and then attempt to upright/stabilize themselves.

That’s my understanding, anyway.

This video from Curious Marc just appeared on YouTube. For those that haven’t seen his channel, he is the ultimate Apollo geek, currently restoring actual Apollo electronic hardware. Well worth a subscription.

This video documents his visit to the Museum of Flight in Seattle, where he views the CM hatch and discusses the markings. His answer is different again. The markings helped during re-entry, and were placed to allow the astronaut in the centre seat to monitor the roll motion that the guidance computer was executing during re-entry. One assumes there were procedures to take manual control if things were going awry.

Thanks for that, Francis_Vaughan. Another angle to pursue.

I found the definitive answer, and it doesn’t involve splash down. The 1969 Apollo Operations Handbook, Block II Spacecraft, Volume 1 (SM2A-03-BLOCK II-(1) paragraph, Window Markings. Also contains a nice drawing. And to be clear, the bezel does not rotate. It’s fixed.

The left rendezvous, right rendezvous, and hatch windows have markings to aid the crew in monitoring the entry maneuver and also function as a visual reference for orientation during a manually controlled entry. After SM separation, the CM will be oriented to a “bottom” forward entry attitude with the crew’s heads and Z-axis pointing “down.” The X-axis will make an angle of approximately 31.7 degrees with the “aft” horizon during most of the entry, so as the commander views the horizon through the left rendezvous window, it will appear 31.7 degrees from the X-axis. During the entry roll program, the actual roll can be approximated by markings on the window periphery that have been pre-calculated by computers. Being a method that requires a fixed-eye position to avoid parallax, the 80th-percentile crewman eye position is used - his eyes are 15 inches aft of the 31.7-degree mark on the inner rendezvous windows. If a crew- man is other than the 80th percentile, he will have to adjust his head/eye position.

Left Rendezvous Window Markings.
The commander, viewing through the left rendezvous window, has window marks that are yellow epoxy ink applied externally on the glass. The index marks are every 5 degrees from -5 degrees to +35 degrees.

Center (Hatch) Window Frame Markings.
Entry begins at 400,000 feet (75 miles). When .05 g is sensed, the G&N system computes the entry path to land at a certain location. The entry involves rolling the command module to control the lift vector. The CMP in the center couch can monitor the entry roll program. At 400,000 feet, the horizon will appear across the 0° ROLL marks. As the CM is rolled, there are 55° R&L, 90° R&L roll marks to compare to the horizon and estimate roll. The black roll marks are on the hatch window frame.

Right Rendezvous Window Frame Markings.
The LMP will also monitor the entry but in a limited degree. The right rendezvous window frame only has the 5° and 35° markings in black.

Figure 2.12-22 labels the “Roll 0°” mark on the center hatch as a “Lunar Entry” reference line, but the description in the paragraph mentions nothing about Lunar entry. I can’t find any reference to it being used in a “horizon check” prior to reaching the moon. And though this manual mentions the center window allows the CMP to monitor the entry roll program, it was the markings on the left window used for the “horizon check” 17 minutes prior to the Entry Interface (EI) which occurs at an altitude of 400,000 ft.
There is a lengthy discussion about this check in the Apollo 15 transcript around the 294:41:54 mark. It also includes the same Figure 2.12-22 from the manual. Again, it’s only the left window being used.

Section 2 of the Apollo Operations Handbook is here:

Apollo 15 Transcript is here:

Figure 2.12-22

I have such a picture. When I was a kid in the early nineties, I’d write polite letters to all sorts of celebrities (or their agents) asking for autographs, include return postage, and hope for the best. NASA obliged. At some point in the 1990s, Armstrong stopped giving autographs after seeing them traded for many among collectors, but I was lucky to get mine before that. It’s one of the treasures of my autograph album, which is the only real collection of anything collectible that I own.