That's pretty wild, Chris. Usually there's a lot of red in those. Where was this taken? We have so many nice sunsets here I've almost become immune to them. Of course, the really striking ones I always see while driving someplace without my camera in tow, I'll have to change that habit. I'm lucky to live in a place that's very visually pleasing and should share it (or boast?).
I've noticed a male/female dichotomy on this one. When I go out with a camera, I get all these pretty pictures (to me) of landscapes, things, places, wildlife, flowers. When my wife (any of them -- I've been around the block a time or few) go out with a camera what comes back is pictures of people.
A really neat thing to do with a large 'scope is get detailed pix of the nearest star, the one that's up when you're awake. I've used mine that way and it's a lot of fun. You can't of course just point a 10" scope at the sun, pretty likely something would burn (might be useful for that...if you could get it lined up first so the "beam" wouldn't hit black stuff in there and all come out). What I did was make a cover plate for the big thing out of cardboard (metal would be better but this was quick and dirty). I punched 4 roughly 1" holes in it around the perimeter, and put filters from those cheap glasses they sell for eclipse watching over them. Then you can point it at the sun and not be totally blinded by it - and retain the effect of a large aperture on resolution fairly well. There's actually quite a lot to see doing that, without even a fancy filter. But the pix with filters are stunning.
Of course, this isn't a slick as having those two-stage single H line filters they used to sell for about $8k...what those did was one for over the aperature would bandpass a fairly wide band in the red, and be somewhat also neutral density to cut the light down some. Then a very fancy filter at the eyepiece could not only select a single H line, but was so narrow it could "see" the doppler of H moving towards you vs away from you, and was tunable (in fact, the issue was IIRC that it would drift and needed tuning to be stable). This let you, in effect, see into the sun, not just the surface. NASA has some in space that have bands up to the deep UV for that, and their pix are really nice.
http://sohowww.nascom.nasa.gov/home.htmlIt turns out the sun is "ringing" at about 10^7 harmonically related frequencies (literally DC to daylight), and a photodiode put in the prime focus pointed at one of the little pockets of vibration can pick this up -- truly the music of the spheres. You don't get a good signal everywhere -- there are peaks and nodes. In other words, you don't see this in a signal from the whole sky -- it averages out.
Now, somebody like Jerry or Joe could contrive to make such a filter (it's all sputtering IIRC)....maybe even for sale. Real sharp filters could have significant uses in fusor diagnostics. Hint.
I believe it's just a ton of different dielectric layers. To get a real narrow one you have to have pretty tight control over all the layer thicknesses. I don't *think* you can get that as well with a diffraction grating, but I could be wrong. Now THAT, I understand is the ultimate challenge for a machinist, much like Chris comment much earlier about "how do you get the first screw threads". It seems to require excellent mechanical design and construction, then some very good realtime feedback as the grooves are cut perhaps using a short wavelength laser interferometer. Tight temperature control is also needed.
I haven't seen it mentioned in optics (I'm no expert), but in regular filter design there are various topologies to get what you want. You might have a bandpass section with a notch filter on either side to sharpen it up right around the bandpass, for example, and there are a ton of possible tricks.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.