The Protective T-ring for the Canon EOS allows Baader filters to be used with a T-ring,
providing the largest possible free aperture of 47.3mm (M48 thread), and protecting the camera
body from dust and humidity. To allow optimal use of the Protective T-ring, several versions of
it are now available with a built-in 50.8mmx3mm or 50.4mmx 3mm Baader filter.
The Protective T-ring not only offers exposures free from vignetting with extremely short focal
length telescopes, it can also be universally connected. Four different types of telescope
connection are included. The adapters of our Astro T-2 system can be used for many other
types of mounting onto a large range of telescopes.
After carefully examining the CANON bayonet fitting we have optimized the fit and tolerances
between the camera bayonet and T-ring. The result is the Protective T-ring, which is wobblefree
and has no lateral play thus always guaranteeing a stable image platform, even for long
exposures or when the telescope slews.
The Protective T-ring replaces other built-in camera filters which are installed directly into the
camera body. All unmounted 50.8mm or 50.4mm Baader filters, and Baader 2" filters mounted
in low-profile filter cells (LPFC) may be used with the Protective T-ring. (LPFC describes all
Baader filter mountings where the effective overall height of the filter cell is not more than 6
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Protective T-Ring CANON EOS
The glass thickness (3mm) of the built-in 50.8x3mm filter is taken into account in the
mechanical construction. The resulting effective overall optical length for each CANON EOS
camera thus amounts to 55mm - precisely the overall optical length of standard T-rings.
If, instead of a 3mm thick filter, a normal Baader 2" Filter with a low profile filter cell is used, the
effective overall height of 55mm deviates from the standard by just +0.3mm. This deviation is
Included in delivery:
1. Protective T-Ring for CANON EOS body
2. Optional: Baader clear protective filter, 50.8mm x 3mm (protective T-rings are available with
a range of pre-assembled filters ??? see price list or the label on the product packaging)
3. Temperature compensation ring (to prevent filter damage at high temperatures)
4. S52/M48 adapter ring (M48 corresponds to the international 2" Astro filter thread)
5. M48/T-2 insert ring
6. S52/2" connector socket (with additional 2" M48 filter thread on the front side)
7. 1.5mm Allen key