NavList:

I notice the last two pictures posted show sextants being used from the interior of the ship shooting "sights" through glass windows.  I would think that the glass would create some kind of extra refraction error or perhaps just an abboration leading to reduced accuracy.  I have no evidence to support this hypothosis,  just seemd like "common sense".  I assume these navigators were demonstrating the use of the sextant (the second photo shows the gentleman taking a sight with the index arm right around zero) for the photographer.  Can someone please confirm this thought or set me straght?  Is it ok to sight through a glass window?  On my Davis AH there is two panes of glass that the light passes through before hitting the sextant but because they are at complimentary angles I assumed this cancled out any error the glass might produce.  Im sorry that this was slightly off topic to the thread but it made me wonder.