(meteorobs) Rayxar X-ray lenses.

Swift, Wesley Wesley.R.Swift at msfc.nasa.gov
Mon Aug 29 14:34:10 EDT 2005


Ed,

	Removing the IR cut filter won't affect the "Blue" but I suspect it
will affect the UV.  Photographic cameras tend to cut the UV to increase
contrast in the presence of haze and lens defocus in the UV.   Most
photographic lenses are quite dark in the UV.  Although IR block filters
tend to be "bulk" filters, if it has a simple interference stack that cuts
700nm it will cut 350nm as well. 

	I have a 12" f/2.5 Aero Ektar as well.   What a glorious mountain of
glass!  You do realize they are radioactive...

	Good luck and keep me informed.

Wes


-----Original Message-----
From: meteorobs-bounces at meteorobs.org
[mailto:meteorobs-bounces at meteorobs.org] On Behalf Of Ed Majden
Sent: Monday, August 29, 2005 1:09 PM
To: Global Meteor Observing Forum
Subject: Re: (meteorobs) Rayxar X-ray lenses.

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

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