Re: Spectrum of Dark Sky
- From: "Neil B." <neil_delver@xxxxxxxxxxxxxxx>
- Date: Fri, 12 Sep 2008 11:14:16 -0400
"W. eWatson" <notvalid2@xxxxxxxxxxxxx> wrote in message
news:h2hrk.7544$np7.5910@xxxxxxxxxxxxxxxxxxxxxxx
In astronomical spectroscopy, it's necessary to subtract out the
background sky before getting to the final spectrum. This seems
reasonable, and most spectral analysis software does this. Is there
any literature on this and the methods used? For example, one s/w
package uses median sampling, while others may use averages.
Are there any spectra available of the night sky taken without stars
in it? I suppose that may sound silly, but I would think someone would
subtract out any problematic star images first. Of course, I may be
missing the point that such spectra are not just of the atmospheric
spectrum, but of all spectral noise of the night sky including the
atmosphere (brightness).
--
Wayne Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
Web Page: <www.speckledwithstars.net/>
Good question, but "needless to say" you must consider the contribution
of varied types of artificial light, many of which have distinct and
strong spectral lines. One surprise I heard of about the natural sky, is
a far red or near IR band of emittance which would be quite noticeable
if our eyes were more sensitive to dim red light.
BTW I suggest readers support dark-skies initiatives, here are some
links:
http://www.darksky.org/mc/page.do
http://www.wetmtndarkskies.org/
http://www.flagstaffdarkskies.org/
.
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