(meteorobs) Rayxar X-ray lenses.

[Ed Majden]

on 8/29/05 10:46, Swift, Wesley at Wesley.R.Swift at msfc.nasa.gov wrote:

> Ed,
> 
> Large format!!!  Yikes!
> 
> Large format, fast optics and low cost are mutually exclusive.
> Since the end result is usually more concerned with the number of
> "resolution elements" in the image, most folks have gone to smaller formats
> with a significant reduction in kilograms and kilobucks.    Glass mass and
> price usually scale with the cube of coverage...  Removing the IR / UV block
> filter from a Nikon DSLR will get you a QE of perhaps 5% at 350nm, which is
> about as good as film.  If you can find the UV-Nikors and a suitable
> aperture grating that might be as good as it gets under a bunch of
> kilobucks.
> 
> Wes

Wes:
    I didn't think removing the IR blocking filter in a DSLR would help with
blue response?  It will extend it into the red a bit.  I have a Canon D20,
unmodified that I'm going to try for spectroscopy if I can get a long enough
exposure without too much noise.  Jiri Borovicka suggested I use high
dispersion and just study the region around 500.0 nm.  The rest of the
spectrum would be off the screen.  I will use a 1200 g/mm large reflection
grating that I have with a Canon f/1.2 - 55 mm lens mounted on the D20.  I
still have to try this.  ITT tells me they are working on an extended blue
response image intensifier but they will be costly!  I have an f-2.5 - 12
inch Aero Ektar lens that will cover an 8X10 plate but operating such a
system would be rather expensive.  A large replica transmission diffraction
grating is also very expensive.  I may try a Learning Technologies thin film
holographic grating, 5X5 inch 750 g/mm. as an experiment.  This will require
a rather bright fireball to get a spectrum.  Such gratings need calibration
and they are not as efficient as a blazed replica grating. I did in fact get
a spectrum with one that is shown on my web page.
Ed