(meteorobs) Off-Topic X-ray film.

Sat Sep 3 18:17:09 EDT 2005

Ed,

I am afraid I have some unfortunate news about your lens. The lens you have is called an "x-ray" lens because it was used to photograph the phosphor screen in an x-ray imaging sequence. I do not know but if any optimizing were done on the design, it would have been for green light if that was the emission color of the phosphor in use. It might perform poorly is the blue and might not transmit much if any UV especially considering the mass of glass they put in those old things.

Actually glass (or quartz etc.) lens cannot focus x-rays. Refraction goes up steeply as UV wavelength increases and finally simply becomes absorption. I work on a project to UV photography of comets from Earth orbit and we used the Nikon UV lens, which as i recall has a rather long focal length for your purposes not to mention the price.

If I can help on this project in any other way, please call on me.

Clear skies,

Terry Richardson
Department of Physics and Astronomy
College of Charleston
Charleston, SC 29424
843 953-8071

-----Original Message-----
From: meteorobs-bounces at meteorobs.org on behalf of Ed Majden
Sent: Sat 9/3/2005 3:01 PM
To: RASCALS
Cc: meteorobs meteorobs
Subject: (meteorobs) Off-Topic  X-ray film.

Hello Rascals:
    Anyone know what the actual spectral response of x-ray film is and
speed?  I know it is blue end sensitive but how far does this extend toward
the red end of the spectrum?  I have a Rayxar 65mm - f/0.8 surplus x-ray
lens I would like to experiment with to obtain near uv meteor spectra.
Unfortunately this lens only covers a small circle about 18 mm in diameter
with the focal plane 0.8 mm behind the rear element.  They also tell me that
it suffers from severe image distortion because of its extreme speed.  I
wonder if it is made of special UV transmitting glass as x-rays are much
shorter than the blue/uv end of the spectrum.  So far I haven't found anyone
that can tell me about the characteristics of these types of lenses!  Anyone
know????  There was a larger x-ray lens on ebay with I expect a larger
format size.  I did not bid on it because I wasn't sure if it would be
useful.  I just discussed this with Ian Halliday via email as he obtained
some near uv-blue end spectra with a special uv transmitting lens that Peter
Millman had ordered.  Ian did not know the characteristics as it was bought
before his time for the Newbrook/Meanook Meteor Observatory projects.  Ian
says the blue end response is limited, because of the atmosphere.  Probably
not usable below 300.0 nm.  There are some interesting features in the
region of 300.0 nm to 400.0 nm in meteor spectra.  The red or near IR end
exhibit mostly atmospheric molecules/atoms of oxygen and nitrogen etc.
Image intensifiers cover this region very well but they have poor blue end
response and are only good from 450.0 nm to around 900.0 nm.  Blue end
intensifiers are being designed but they will be very expensive even if
obtainable by non U.S. residents.
    I look forward to any comments!

Ed Majden  B.C. - Fireball Network Coordinator - AMS Meteor Spectroscopy
West Coast Sandia Bolide Detection Station
Courtenay B.C. CANADA

http://members.shaw.ca/epmajden/index.htm

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