Rainbow on my bedroom ceiling

I was lying in my bed this morning, trying to summon the energy to wake up when I noticed a faint rainbow on my bedroom ceiling. There is a large picture window at one end of the bedroom and a window shade over it. There is a small gap at the top of the shade (also along the sides) that lets some light in. The window faces NNE so by 8:30 or so the sun (it was a bright sunny day) would have been nearly parallel to the window. The rainbow was a line parallel to the top of the shade, so I assume there was some kind of diffraction effect, but I don’t understand it.

Mrs. _Seldon: Would you roll over and go back to sleep?


Mrs._Seldon may have hung a light catcher on the back deck.
Voilà! rainbows!!

Water, acting as a prism.
It couldn’t have been Iron, because Iron bars do not a prism make.

Whenever I see something like this, I put my hand there so it’s projecting on my hand, and then move the hand back to keep the projection on it until I find the source.

I suspect it’s much more likely to be a refraction effect than diffraction.


I flew through one once. It was really cool. It changed as I got closer and just before I flew threw it the arc enveloped the plane so that the rainbow wrapped around in a circle.

You were dreaming.

Welcome to my world.

Not that I fly, but I have always wanted to see a 360° rainbow. Lucky!

I have seen a “moon-bow” at Victoria Falls in Zambia/Zimbabwe. There is a fairly constant rainbow there due to the spray, but moon-bows are rare, they require a clear sky and a full, or very close to full moon.

I think it was diffraction by the edges of the slit, which creates an interference pattern. The image below shows for monochromatic light, which results in a pattern of dark and light areas. With white light, each wavelength has a different pattern, resulting in a rainbow.

You can see this effect by looking at a bright light through your fingers with a tiny gap between them.

It could not have been refraction. It was dry and there is nothing to refract through. The window is flat, at least to a high degree. The other slit is in the shade. The window is so tall (I would guess 12 or 13 feet) that the shade is sewn together in two parts with a horizontal seam. The seam is quite visible and the rainbow was also parallel to it. If it happens again (it might be dependent on the exact angle of the sun in which case I might have to wait another year), I will try lowering the shade and see if the rainbow moves. The seam is too high up (and too wide–the width of the room) to block with my hands.

Sadly the phone I used to take pictures of the event died. Even though the pictures weren’t high resolution they told a story. As I got closer to the rain that created it the area under the rainbow got brighter. I’ve thought of taking the dead phone to someone who might get it to boot up long enough to download the photos. It’s not like it’s something I could ever replicate. It also took with it all the photos from the Oshkosh air show I was returning from. Ugh, and it had photos of my buddy who taught me to fly and has since passed away.

I’ve never seen a 360º rainbow, but I saw a 270º one once from my 9th-floor apartment, and another one of about 190º dipping into Yellowstone Canyon.

It’s not possible to “fly through” a rainbow as Mcgiver describes. A rainbow is always a 42-degree wide circle from any viewpoint. I suspect it was a Glory, which is commonly seen from airplanes.

It was nothing like the cite you listed. It looked like a standard rainbow. You could clearly see the line of rain that created it. As I flew through the rain it became circular. I wish I had the pictures to link to.

I don’t think @Magiver suggested he flew through the rainbow, just that he observed a full circle rainbow.

I have known that this phenomenon is possible since early childhood (7yrs? 8yrs? I can’t recall) as I was an avid reader of books of facts and trivia.

I have seen an aurora of the sun, which I assume you mean by “sun dog” - I was tripping on LSD but accompanied by a sober friend who confirmed it. The two phenomenon are very different.

I’ve seen a double rainbow. It filled the sky over a highway and was very pronounced. Every car we saw people were pointing at the sky.


Double rainbows are a fairly common phenomenon. Note that because the second one is the result of an additional internal reflection in the raindrops, the color order will be reversed from the first one.

Now if you want rare, try to find a triple rainbow.

Rainbows were really common when I lived in Montana, including rainbows with all of the optional extra features, like a rainbow at sunset (so it’s the full 180º), with secondary rainbow, anticrepuscular rays, and supernumary bands.

Triple rainbows are tough to find, not only because they’re as much fainter than secondaries as the secondaries are than the primaries, but also because they’re on the other side of the sky.