Postcard of the Day

[fflo]

 

Comments

[peteralway.livejournal.com]

Ooh! Once upon a time, in high school, I bought a bunch of astronomy postcards published by Hansen Planetarium. They came as wall posters, too (and I bought a bunch of them). The photos were from Palomar Observatory, as well as some NASA shots. In the 70's, there was sort of a standard set of Palomar color photos, mostly taken with the wide-angle 48-inch Schmidt camera. This shot of the Pleiades is one of the 48-inch Schmidt shots. Those photos were ubiquitous in the 60's and 70's. I think some of them were even on the bridge of the Enterprise in the original Star Trek. This same photo showed up in a lot of astronomy books, because it was simply the best Pleiades shot around.

I think it's interesting that the diffraction spikes around the stars sort of became what people assumed stars really looked like. They are actually an artifact of the "spider" beams that held the photographic plate in place in the middle of the telescope in front of the mirror.

Those shots seem to have fallen out of favor, both because of Hubble, and because amateurs with digital cameras can produce pretty pictures just as good or better these days.

[fflo.livejournal.com]

I had a feeling you might have something to say about this one, but this wealth of info is especially nice.

The spikes reminded me of when I have something on my glasses, which seems related, sorta.

Cool that your astronomical knowledge (both senses intended) makes you, in this case, a pretty good dater of an old postcard.

[peteralway.livejournal.com]

They are related to what you see in your glasses or on a windshield in that the are perpendicular to the lines that cause them. The vertical diffraction spikes are caused by the horizontal beams of the spider, and the horizontal spikes are caused by the vertical beams.