Periscope depth question

[virtualpender]

I had the chance to visit the PAMPANITO over the weekend and noticed the shallow depth gauge in the control room had markings at the following depths:

48 1/2'
66 1/2'
150'
I'm assuming the 150' is the "crash dive" depth. I am correct to assume that the other two values are the minimum and maximum periscope depth and that the middle value between the two (57 1/2') is the standard periscope depth?

Here's a photo (not mine - this one is from COBIA) illustrating what I'm asking about. Anybody know for sure?

http://i205.photobucket.com/albums/bb93/kikn79/USS_Cobia/Control%20Room/tn_DSCF5640.jpg

[BillBam]

Probably radar and periscope depths.

[tomoose]

Periscope depth would be a safe bet for one of them. The other could be, as mentioned, radar depth (i.e. raising the radar mast). Is it possible that the deeper one could be max depth for opening torpedoe tubes or firing torpedoes?

[virtualpender]

Radar depth was generally 40' according to several sources so I think we can rule that out. 67 1/2' seems awfully deep for periscope depth since the scope tube was 40' overall.

[Frumpkis]

I'd go with Tomoose's guess that's it's maximum depth for firing torpedoes. The deeper you go, the more compressed air it takes to shove out the fish, and (IIRC) the air pressure was fixed, not variable for depth.... something like 500-600 psi.

[Admiral8Q]

In my opinion, it was probably radar depth on the first one, the PD on the second. The last I cannot guess.