Starship Asterisk*

In support of the window glass reflection explanation for the "triple sunrise" discussion (APOD 4 August 2009), these are some pictures of a sunset which I took in Primosten, Croatia, in May 2006 around 6:30 PM local time. DSCN6533 is a standard image from a balcony outside my hotel room. The others are from the reflection on the double sliding glass doors of the balcony (pointing towards the inside of the room, see DSCN6528). The more closely zoomed image is also reflected in the glass but could might pass for a "direct" photo (DSCN6535).

The photos were taken with a Nikon Coolpix E4500 digital camera at ISO 200 (further data are embedded in the EXIF file). They have been further compressed in Photoshop to meet the submission size. This is my first submission to APOD, and I am not sure whether the images were properly attached. I would appreciate feedback on this respect.

Sincerely,

Rafael I. Barraquer
rbarraquer@telefonca.net
Barcelona, Spain

Complementary to my previously posted photos on "Multiple sunset", this is the initial image that first attracted my attention. The many reflections are probably due to the two sliding glass doors overlapping -plus possible reflections from the inner curtains?

R.I.Barraquer

I spent over an hour looking at the first several pages of this thread. It seemed oddly familiar somehow. Then I went to bed and saw the double reflection of the red radio tower light some quarter mile from my relatively new double glazed window. I believe the window was manufactured somewhere near sea level and shipped to Los Alamos at 6 to 7 thousand feet and has somewhat of a bow in both panes of glass, the outer one bows out, the inner one in. I can see the reflection on the left or the right of the direct image, depending on which side of the window I view it. I tried pencil and paper ray-tracing the results and got nowhere until I realized that the image and the reflections were not the result of a transmission and a reflection of the same ray. Assume that the rays from both images converge at the eye (obviously true since the eye/camera is seeing both rays coming from different points) and trace the rays backward. The result is two parallel (effectively so) rays leaving/impacting the glass at different points. Thinking time forward again it is the non-parallel glass that deflects two separate rays so that the reflected ray of one converges with the direct, non-reflected path of another at the eye. Move the eye to a different point, and it sees two different rays that react differently.

I have probably missed something – perhaps that someone else has suggested the same thing and been shown to be wrong in the many pages that I skipped, if so, my apologies.