||589 nm first order image of reflection of sodium vapor lamp|
|F||589 nm second order image of reflection of sodium vapor lamp|
|G||Zero order, incandescent lamp|
|H||Blue end of first order, incandescent lamp|
|I||Red end of first order, incandescent lamp|
|J||Zero order, mercury lamp|
|K||First order 404 nm mercury|
|L||First order 435 nm mercury|
|M||First order 486 nm hydrogen|
|N||First order 546 nm mercury|
|P||First order 656 nm hydrogen|
|Q||Second order 404 nm mercury|
|R||Second order 435 nm mercury|
|S||-1 order 404 nm mercury|
|T||-1 order 435 nm mercury|
|U||-1 order 486 nm hydrogen|
|V||-1 order 546 nm mercury|
|W||-1 order 579 nm mercury|
|X||-1 order 656 nm hydrogen|
|Y||Zero order, reflection of mercury lamp|
|Z||First order 404 nm mercury from reflection of lamp|
|a||First order 435 nm mercury from reflection of lamp|
|b||-1 order 404 nm mercury from reflection of lamp|
|c||-1 order 435 nm mercury from reflection of lamp|
|d||-1 order 486 nm hydrogen from reflection of lamp|
|e||-1 order 546 nm mercury from reflection of lamp|
|f||-1 order 579 nm mercury from reflection of lamp|
Once again, serendipity has reared its head (see my TEDxUIUC talk). I went to the museum to get some material for my blog, but what you’ve read here wasn’t what I was looking for. When I was a postdoctoral fellow in 1978-1979, I visited the same museum, and at that time there was an exhibit with Henry Rowland’s original grating ruling engine – complete with a foot switch to step on so I (or any visitor) could rule the next groove on a piece of speculum metal. I figured description of early grating ruling engines, grating replication and how holographic gratings are now replacing ruled, replica gratings in many cases would make an interesting blog post. But look what happened instead!