Does the Canon 60Da offer significant advantage over 60D with infrared filter for astrophotography?

Question

I am looking to buy a new camera to upgrade from my 1000D. I found the 60D to meet most of my needs but came across the 60Da variant when trying to make a decision.

The price difference is considerable between the 60D and his "A" brother, the 60Da, and I would like to know if any of you have or tried and compared these cameras for astrophotography. I want to mention that although I won't be taking pictures of the sky very often, but mostly portraits, I would like to have this possibility available at any time.

In that sense I would like to know which situation is more advantageous, a 60Da or a simple 60D with a infrared filter? How do the results from these cameras compare to each other and can you improve and/or best a 60Da's photographs in a astrophotography context with a 60D paired with good infrared filter?

Answer 1

It's probably best to think of the 60Da as special-purpose astrophotography gear. In order to get the increased Hα sensitivity, Canon have modified the IR-cut filter that sits in front of the sensor, letting in quite a bit more light in the near-visible IR range. You can't see that light, but the camera can. For day-to-day photography, then, you'd need to add an IR-cut filter to your lenses—or you'll wind up with the same sort of problems that Leica M8 shooters had. "Blacks", in particular, will show up as various shades of magenta and brown, but the IR false colour can significantly contaminate other colours as well.

(There is, apparently, a body-mounted IR-cut filter on the market, similar to that used in the Sigma SD1 Merrill, but it is incompatible with EF-S lenses.)

On the other hand, you can't achieve the same results for astrophotography using a normal 60D and a filter. Since the sensor-mounted IR-cut filter reduces the camera's sensitivity to hydrogen-alpha (and similar wavelengths), you would need to reduce the sensitivity to other wavelengths to a similar degree using an IR-pass filter. That will mean that you'd need to increase exposure times considerably or bump up the ISO by several stops. You can correct the exposure time problem (to a degree) using a tracking mount and making sure that the LCD is flipped out away from the camera body, but if you want any terrestrial foreground, you're stuck with higher ISO and noise.

The 60Da is an option, but only if astrophotography is a big enough part of what you do to warrant having a filter, with all of the drawbacks of having an extra optical element, on your camera for most of the rest of your shooting.

Answer 2

Here is an initial overview of 60Da, also lists out some technical differences between 60Da and 60D. You can also find a good discussion on flickr about shooting IR with a 60D. According to one of the comments, and other sources, "Most DSLRs (including the 60D) have a filter built in that blocks infrared light. Before one could consider doing infrared photography, you'd need to physically alter your camera" - so unless you are feeling adventurous to alter your camera (I think LifePixel does the conversions, you can also find their DIYs here - though they don't have one for a 60D), I would say go with a 60Da.

I want to add that even if you did alter the camera, you might not get satisfactory results.

Answer 3

It's far more cost effective to have a 60D modified for astro work. Google Gary Honis. I and several of my astro friends have Gary Honis modded cameras (40D, T2i, T3i). With the milder modification you can shoot astro and get hydrogen alpha light, but use a custom white balance for daylight. More drastic mods, like replacing the UV/IR block filter on the sensor with clear glass, make it difficult at best to do 'normal' photography. 60Da hasn't come down in price at all, I suspect that's because folks who want modified cameras realize it's no price bargain. When the 20Da came out it was kinda the only game in town.