21.5 hours on the lunar surface
Distance to the moon: 238,900 mi
Length of VAB =37000 miles
Time to the moon:
Translunar injection engine cutout 1:40:50
Lunar orbit insertion 63:23:27
Elapsed time: 61:43:37
Average rate of travel: 238900 miles/ 61.76666 hours = 3870.92 miles/hour
We know that Apollo 11 entered the TLI at 24200 mph @ 12:22
We know that 2 hrs. and 32 minutes later it had traveled 22000 miles
22000/2.53 hrs. = an average speed of 8695.65 mph.
We know that the VAB is 37000 miles long
22000/37000 = 59.5% of the VAB had been crossed
After 2.53 hours the Apollo 11 was traveling 12,914 feet per second.
12914 ft/sec * 3600sec/hr * 1 mile/5280 ft = 8805 mph
37000-22000 =15000 miles of VAB left to travel @ 8805 mph slowing
15000 miles/8805/miles/hr = 1.7 hrs plus 2.53 hours = 4.23 hours but let’s round it to 4.30 because the Apollo was in constant deceleration throughout the VAB transit.
Now the lowest radiation area in all of the VAB is the blue region which is .0001 rad/sec
.0001 rad/sec * 4.5 hrs * 3600 sec/hr * 10 mgy/rad = 5.22 mgy
5.22 mgy/8days = 0.6525 mgy/day
Now if we assume GCR of .24 mg/day and lunar radiation raises that 35% then 1.35* .24 mg/day = .324 mg/day for 2 days lunar orbit and 1 day on the surface or 3 days.
.324 mg/day * 3 days = .972 mgy
.972 mgy from lunar orbit and lunar landing plus 5.22 mgy from VAB transit plus 5.22 mgy return transit through the VAB = 11.412 mgy
11.412 mgy/8.33 days = 1.369 or as I originally said a full magnitude less than it should be.
https://history.nasa.gov/ap11ann/apollo11_log/log.htm