I’m not sure why you decided to be so snide in your comment; especially since my reasoning was clear in this post — and I’ll note you inferred I didn’t know what an extinction coefficient is, which is simply not true.

And if you’d fail a first year for a mistake like that… well, I’m glad you were never my professor. Better students learn from mistakes than be punished for them.

Everyone else, sorry.

There was a project by the Independent Space Research Group (originally a group of RPI students) that was building a 50cm telescope to be launched as a get-away special (GAS) cannister on the Shuttle in 1987. They disappeared, and I can find little about them on the web. I think they lost their ride after the Challenger disaster. I found a link to them, but it appears the server is down. It might eventually work.

There was also a project to build an amateur telescope to be mounted on the ISS (the ISS-AT) , but the project web site is defunct. Maybe it ran into problems after Columbia?

Now there’s a huge bite taken out below 400nm; that is partially due to scattering and closer to 300nm it is due primarily to oxygen and ozone (but there is also significant absorption by other trace gases); below ~280nm water vapor also absorbs UV very well and the atmosphere is pretty much opaque.

On the longer wavelengths it should be obvious that many of the features are due to absorption by the atmosphere. Astronomers with instruments on the ground are forced to study the near infrared region only in those parts where the atmosphere is transparent; there are no such restrictions in space.

What do we need Phil say? What is there to say, that you didn’t just say yourself? With heavy light pollution, you’ll see few stars if any. Move to where the sky is dark, and you’ll see many more. Everyone already knows this. Heck, I was on the Strip in Las Vegas, and the only thing you could see in the sky was Jupiter (which I thought was pretty impressive of ol’ Jupes).</i.

The celestial object that most impressed me versus overwhelming light pollution was comet McNaught (2007) seen from the Adelaide oval in the centre of my (admittedly small by international standards) city with all the light towers on in evening twilight around sunset but whilst still quite light after a day-night cricket game. Now *that* was impressive!

Nothing too unusual or to be too ashamed of there methinks. Often we learn more through our mistakes than what we get right.

@38. mike burkhart : “Nobodys perfect I have made plenty of mistakes like my spelling.”

Agreed there. As for typos & spelling errors .. I could swear that my #@!&^$^$#@@! computer adds them to my posts in just that final second before my editing time runs out!

.. & when I see them I usually do!

———

* & mea culpa myself there.

This is actually a triple coincidence:
1. Visible light is the peak of the Sun’s radiation curve. This would not be the case if it were much hotter or cooler.
2. The atmosphere is much more transparent to visible light than longer or shorter wavelengths.
3. Visible light has enough energy per photon to induce chemical effects (i. e., vision) but not so much as to damage biological material.

Dust and volcanic haze will increase the extinction at all levels, but in a fairly ‘gray’ (wavelength independent) way.

As for the red and blue lines – I stared at this for a while but I think I finally figured out. The red line is the direct solar irradiance after absorption by 1.5 airmasses, but the blue line is the direct solar plus the scattered solar in the whole hemisphere seen by the solar cell. Basically, if you did a spherical integration over the hemisphere except where the sun is (e.g., collect all the blue sky), you would get the difference between the blue and the red curves. The difference between the blue and black curves in the visible is then light that is scattered back into space.

So for the problem considered, the red line would be the one to consider for starlight. The blue curve is only relevant to a solar cell that collects light over the whole hemisphere.

I suggest you do another followup, Phil, to discuss light pollution. As other commenters have pointed out, that’s a major effect that you seem to be neglecting. [snip] Try looking for stars in Manhattan. You might see Sirius on a good night. Now go to the Mojave on the same night and you’ll see thousands of stars.

What do we need Phil say? What is there to say, that you didn’t just say yourself? With heavy light pollution, you’ll see few stars if any. Move to where the sky is dark, and you’ll see many more. Everyone already knows this. Heck, I was on the Strip in Las Vegas, and the only thing you could see in the sky was Jupiter (which I thought was pretty impressive of ol’ Jupes).

@Joseph G – Yeah, basically. The dips can be absorption, but also reflection.

@#21 rob: I had no idea a 1 watt laser was so powerful. I guess it’s the inverse-square law at work? Or lack thereof?

@#26 mader: Corollary to rule 34: If it exists, there is a forum for it.
Incidentally, I’ll never be able to pet a horse again.

@#9 Daniel: So if I suck pure, pressurized oxygen, my eyes will get more sensitive, temporarily?
Until the oxygen toxicity makes my brain bleed, anyway.
EXTREEEEEME ASTRONOMY! OHHHHH YEAAAAAAAAAAH!

(Note: the smileys if you think I’m serious)