Rainbow
Rodney Blackall
<sundogs...@dial.pipex.com> wrote:
> > As the view opened up I could see it was a full rainbow but because
> > of the darkness could only make out the colours at each end - but
> > they were clear
> -snip-
> > is it a common phenomenon?
> Rainbows produced by the moon are fairly rare because they are much
> fainter than their solar companions and so go unnoticed. Colour
> vision is not very effective for dim objects so they usually appear
> uncoloured. You were lucky!
QUESTION: what colour is moonlight? Is it white, i.e. all colours mixed
and hence capable of giving a rainbow, or is it changed by the Moon's
surface?
Anyone seen a spectrum of moonlight?
--
Rodney Blackall (retired meteorologist)
London, ENGLAND
Using Acorn SA-RPC with ANT INS and Pluto
Stephen Tonkin
topic]
Rodney Blackall <rbla...@rodsrisc.demon.co.uk> wrote:
>QUESTION: what colour is moonlight? Is it white, i.e. all colours mixed
>and hence capable of giving a rainbow, or is it changed by the Moon's
>surface?
It is essentially reflected sunlight -- the lunar surface reflects light
in a manner that approximates to tarmac.
>
>Anyone seen a spectrum of moonlight?
Yes -- both in a spectroscope, and in parselene photographed by Bob
Mizon. It is a continuous spectrum. If you don't have a spectroscope,
you can make a simple one using a CD. All you need is some arrangement
by which light from a slit is diffracted from the surface of the CD. My
"CD" one uses a CD fragment and a couple of flock-lined section of waste
pipe, with a slit at the end of one, all held together with gaffer tape.
I've just photo'd it -- if I remember, when I post this, I'll upload it
to:
http://www.aegis1.demon.co.uk/spectroscope.jpg
As an alternative, Dave Randell has a much simpler system that uses a
complete CD, and the CD box to form the slit!
Noctis Gaudia Carpe,
Stephen
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Tim Hicks
Stephen Tonkin <s...@nospam.demon.co.uk> wrote in message
news:FFdSVAAu...@aegis1.demon.co.uk...
> >Anyone seen a spectrum of moonlight?
>
> Yes -- both in a spectroscope, and in parselene photographed by Bob
> Mizon. It is a continuous spectrum. If you don't have a spectroscope,
> you can make a simple one using a CD.
Out of curiosity, is there any way to "visualise" spectroscopic data other
than actually looking at the spectrum itself. I guess what I mean is; is
there a way to obtain a spectrum in a data format without serious scientific
instruments costing the earth. Perhaps with some sort of CCD plus
appropriate software?
The reason I ask is that I am quite badly colour blind, so while the
spectrum is pretty, I seriously doubt I would be able to interpret it in any
useful way (not that I'd know how anyway).
Tim
Stephen Tonkin
Tim Hicks <tim....@lhsl.co.uk> wrote:
>Out of curiosity, is there any way to "visualise" spectroscopic data other
>than actually looking at the spectrum itself.
Yes. If, for example, you project the spectrum onto a CCD chip, you can
read out the count for each pixel to produce a line graph. Obviously the
wavelength axis needs to be calibrated, but this is possible against
fluorescent lamps (e.g. mercury, neon) or stars (known emission or
absorption lines).
I ought to state now that I am a relative beginner at this game -- I've
been mucking about with home-made stuff for decades, beginning with
using a vinyl record (a Monkees one I "borrowed" from my sister on the
grounds that it was useless musically and therefore it was entirely
moral to investigate its scientific potential, if you must know <g>) as
a reflection grating, and graduating recently to a Rainbow Optics
grating, which I am still experimenting with when weather permits.
If you want to see what is possible with amateur kit, try the Forum for
Amateur Astro-Spectroscopy site (http://www.erols.com/njastro/faas) or
Maurice Gavin's website (http://astroman.fsnet.co.uk), both of which are
pregnant with information from experienced people and both of which have
numerous links to other spectroscopers.
Tim Hicks
> Not at all OT, Tim. (IMNSHO, of course.)
>
> Tim Hicks <tim....@lhsl.co.uk> wrote:
> >Out of curiosity, is there any way to "visualise" spectroscopic data
other
> >than actually looking at the spectrum itself.
>
> Yes. If, for example, you project the spectrum onto a CCD chip, you can
> read out the count for each pixel to produce a line graph. Obviously the
> wavelength axis needs to be calibrated, but this is possible against
> fluorescent lamps (e.g. mercury, neon) or stars (known emission or
> absorption lines).
Thanks Stephen. There looks some interesting stuff there for the "spectrally
challenged"!
I'm not sure I know anyone who would admit to owning a monkees album, but a
particular member of my family has a Cher CD. Would you consider that fair
game?
Tim
Steve Jarrett
Tim Hicks <tim....@lhsl.co.uk> wrote:
| I'm not sure I know anyone who would admit to owning a monkees album,
but a
| particular member of my family has a Cher CD. Would you consider that
fair
| game?
Don't you get CDs mailed to you from ISPs begging you to sign up with
them? I regularly find my doorway cluttered with the darn things.
And just think all this time, they weren't really sending me free internet
offers, but free spectroscopes! ;-)