20D vs. 20Da

What's the difference between the 20D and the 20Da?

the Da has a limited functionality live view for astrophotography. Hence the 'a'.

http://www.dpreview.co​m …506/05060101can​on20da.asp

As far as I know, 20a doesn't have the low pass IR filter that cuts off IR normally for every day picture and then its tweaked for better rendering of deep sky.

The 20Da is a specialised version of the 20D with various enhancements, including I believe live-view and a different (no?) AA filter, for astronomical photography, introduced in early 2005. It is/was very expensive - did Canon even announce a price as it says "Price: open" on the website? - compared to a standard 20D. I think it was only officially available in Japan.
Not therefore an everyday use body! Unless you are an astronomer............​...

OK, thanks. The only reason I asked was because the Canon support page has it listed in their software updates page. I had never heard of the 'a' version before.

A nice explaination:
http://en.wikipedia.or​g/wiki/Canon_EOS_20Da

As I understood it, the 20Da didn't need a special screw-in IR blocking filter to shoot normal images unlike after-market IR conversions that have had their IR cur filters completely removed. A very limited number of the 20Das were made and finding one now is quite difficult.

Read this. Beside being informative, the images presented are absolutely bbeautiful.

The 20Da is not an IR camera. That is, it is not a camera with its IR-rejection filter removed. It does not take good IR pictures, any more than an unmodified 20D will.

What it is is a camera whose filter is especially configured to pass the 21cm "hydrogen" color line, which is partially suppressed with standard LP filters.

This filter modification causes a slight red shift with normal (terrestrial) photography. This may be compensated for in two manners.

1: Through the use of a special lens filter that will suppress the 21cm hydrogen line.

2: In post-processing if shooting is done in raw (not JPEG).

A review of the 20Da (which has been discontinued) may be found here.

20droger wrote in post #4247066
...What it is is a camera whose filter is especially configured to pass the 21cm "hydrogen" color line, which is partially suppressed with standard LP filters.
...

Just as a point of accuracy, it's the 656.3 nm hydrogen line. A wavelength of 21cm is well into the radio part of the spectrum.

You're right. My bad.

By the way, I like your new avatar 20droger.

Thanks. It's just a little neighborhood kitty.

My old one was a cat's head from a celtic emblem.