Canon EF 200mm f2.8 L USM II
|Angle of view (Canon 350D)
||6.354 deg horizontal
4.238 deg vertical
|Sampling: (Canon 350D)
||6.621 arcseconds per pixel
|Best f-stops for astrophotography
||f3.2 okay; f3.5 sharp; f4 very sharp
- This is a fast, sharp telephoto lens. It exhibits less spherical aberration
(coma) or color dispersion (color fringing) than other inferior lenses. It is well
suited for astrophotography using a Canon DSLR (eg. 350D, 50D, etc.). It is not a
zoom lens, however that is one of the reasons it is so sharp across the whole field of
- The lens used in combination with an APS format Canon DSLR is suitable for
wide-field targets up to 6 degrees wide.
- Wide-open, at f/2.8, it exhibits noticeable aberration in the center of
field. However, by stopping down the aperture just a little bit to f3.2 there is a
- In summary, at f3.2 it's okay, at f3.5 it's good. At f4 it's very good and
f4.5 should satisfy the meanest eye - right out to the edge of field.
- The automatic focusing feature is accurate enough to get you started. Set
the lens' focus mode to auto, focus it automatically on a very bright star. Then
take a 15 second exposure and check the results on the computer. Do this several
times and retry the automatic focus and so get the best focus (smallest stars) that you
can. When you've got the smallest stars possible (it should only take you 5 or 6
tries) set the focuser switch to manual and then, if you don't bump the focuser in the
dark, you're in for a good night of photography. I still use DSLRFocus to get the
best focus possible.
- The lens comes with a nice long hood as standard (see picture lower-right), which
really saves having to make one. Getting it on and off requires only a quick
push/pull with a twist. The hood is perfect for delaying the onset of dew and really
helps keeping stray light off the lens. The only downside is getting the lens cap on
and off (to take dark frames) is tricky if you've got fat fingers.
- I've used the 200mm lens to take several images (see examples below) and I can
say that this lens (and also its little buddy, the Canon EF
50mm f1.8 II) represent good value for money.
- Objects that are particularly well suited to the 200mm lens' field of view are:
Large Magellenic Cloud (just fits snuggly in) [click for first
light pics 06Jan08]
- also in the frame for future shoots are:
The Small Magellenic Cloud
Flame and Horsehead in the one frame (easy)
Lagoon, Trifid and the surrounding Milky Way star field wow!
Carina, the Wishing Well Cluster and surrounding Milky Way
The Sagittarius Star Cloud
& M47 pair of clusters
Table of Scorpius
This is a (1:1) crop from slightly off-centre of an
image taken at f3.5
You're supposed to use a telescope for this object...
Last Updated - August 2009 B.C.
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