Hi Stan,

----- Original Message -----
From: "Stan Gorodenski" <stanlep@...>
To: "Spectro-L" <spectro-l@yahoogroups.com>
Sent: Monday, June 29, 2009 5:59 PM
Subject: [spectro-l] Flat Fielding Light Source


>
> Just today I saw GE has a new bulb called a Reveal bulb. Robin, I saw
> you made some comments about this bulb in the AAVSO discussion group but
> am not sure if you were endorsing it or not. I am guessing there may be
> problems with using this bulb for two reasons: a) it says "With Halogen"
> which sort of implies it has something else that would detract from a
> black body continuum, and b) the bulb glass has something in it called
> Neodymium which filters out the "Dull Yellow Rays", as they describe it.
> Hence, the spectrum would be stronger in the blue, it seems.

I think the Reveal bulb would be a non starter for spectroscopy as Neodymium
glass has a strong absorption band around the Na D line area. This is why it
is sometimes used as a light pollution filter. eg
http://www.astrosurf.com/buil/filters/baader_moon_2.png

Robin