The correct time difference between Titanic ATS and GMT was 2h 58m. (See: Enigma). Thus at 3:00am GMT it was 12:02am Titanic. The star positions for 03:00 GMT are about 40 minutes post collision. The iceberg was only about 70-75 ft above the water at its peak. The crow's nest was about 90 ft above the water. Procyon would have been too high to be eclipsed by the iceberg.Thanks for that Samuel. This is close to the star positions I posted, but 3:00 GMT and the co-ordinates of the wreck site are not the exact positions of the stars corresponding to the time and location of Titanic's collision, so I would expect them to be slightly different. I suppose what is most interesting is determining the exact angle of the star Procyon (Alpha Canis Minor) immediately before before the collision, since this bright star was probably obscured by the iceberg at some point and might have given the bridge, if not the crows nest, advance warning of a collision. However, to be sure we would need to know the exact position of Procyon and the height of the iceberg. I'm trying to calculate the first part for the time being, then work out how big the iceberg would have to be to obscure the star.
My whole calculation is based on the collision happening at 02 hr 38 min GMT; that is 2 hrs 40 min before Titanic sank at 5hrs 18 min. The last time is obtained from your book, or at least a reference to it. (Halpern, Samuel 2011. "Account of the Ship's Journey Across the Atlantic". However, searching on the web, there are several other times being cited such as this from the Royal Meteorological Society which states the collision happened at 03:10 GMT. This would mean the Titanic sunk at 05:50 GMT rather than 05:18 GMT. Here's more, & here's some more times on this forum. Am I using the correct GMT time? I'm not sure what 'Midnight' refers to exactly, since the planetarium software could have based it on any of these GMT times.