Here's what the astrophotography web site, "Catching the Light" by
Jerry Lodriguss has to say about the Canon 20Da camera:
http://www.astropix.com/HTML/I_ASTROP/NIK_CAN.HTM
"Red Sensitivity and Long-wavelength Filters
Normally the CMOS and CCD chips used in DSLR cameras are sensitive to
red light. Most DSLRs however, are designed with a built-in, low-pass,
long-wavelength cutoff filter in front of the sensor. The low-pass
characteristics of the filter are designed to prevent moire. The long-
wavelength filtration is designed to improve color reproduction and
make it more like our human visual perception.
The problem is that the long-wavelength filtration also filters out
most of the light at 656.5nm, the wavelength of hydrogen-alpha. This
is the red light of emission nebulae. Filtering out most of this light
is a problem for astrophotography if you want to take pictures of
these red nebulae, which are some of the largest and most beautiful
objects in the night sky.
Canon was the only manufacturer to make a DSLR camera body
specifically for astrophotography with improved hydrogen-alpha
sensitivity, the EOS 20Da. Canon however, has discontinued production
of this camera as of the spring of 2006.
It is possible to modify other DSLR cameras for astrophotography of
emission nebulae by removing the low-pass, long-wavelength filter.
This, of course, invalidates the warranty and runs the risk of ruining
the camera if not done correctly. However astrophotographers have
successfully removed the filters in both Nikon and Canon cameras and
produced excellent images of objects with emission wavelengths."
Diana
Delivered-To: [email protected]
Date: Tue, 30 Sep 2008 18:31:56 -0700
From: "Wally Pacholka" <[email protected]>
To: "Robert Tait" <[email protected]>
Subject: Re: Astronomy Picture of the Day
Robert,
It's a real photograph using a modern digital camera 20d, 5A, new
rebel all work, iso 1600 cranked to 4000 or so, less than 30 sec
exposure to freeze the stars as points, f/1.6 with 30mm lens or so,
cresent moon setting to light the landscape, flashlights.strope to
light the inside of the cave, 5 trips there at 1200 miles round trip
each - no kidding, 2 mile hike with last park being down a very steep
canyon wall, getting lost each time coming out each of the 5 times
and
hard skin to fend off the you faked it in photoshop do nothing
armchair folk, plus 40 years experience and a high degree of
crazyness
to get the perfect shot that few people will believe anyway.
My reward - knowing I got the shot of a lifetime - APOD 29th times,
TIME-LIFE Pic of year 3x, etc...
Wally Pacholka (search)
Night Sky Gallery
562-397-0591 Cell
562-268-4291 Fax
[email protected]
Web site: darkskygallery
* * * * * * * * * * * * * * * * * * * * * * * * * * * *
Diana R. Tomchick
Associate Professor
University of Texas Southwestern Medical Center
Department of Biochemistry
5323 Harry Hines Blvd.
Rm. ND10.214B
Dallas, TX 75390-8816, U.S.A.
Email: [email protected]
214-645-6383 (phone)
214-645-6353 (fax)
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