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My first astro camera was a Nikon D70. At the time the hot camera was a Canon 10D but it was a bit outside my budget at the time.
Since then I have had several Canon 20Ds (I modified several myself) plus a Canon 40D.
It was an excellent camera. A few points about it though and these may no longer be valid as Nikon has obviously progressed a long way from then.
The D70 had the same sensor as the Starlight Express MX25C.
It did suffer from amp glow and it would be a purply corner that would grow to be quite extensive after about a minute.
So you had to use the noise control system which doubled exposure time. Or use library darks.
Nikon's RAW file system is not a true lossless file. A smoothing filter is applied regardless of settings that can damage faint stars. A lot was posted about this but I myself saw little difference. There was a physical workaround to prevent the filter from being applied which consisted of taking the imaging and then turning the camera off straight away. The firmware does an emergency save of the last image but no incamera processing is done.
I modified my D70 myself. It was a lot easier to do than the several Canon 20D's I modified.
Opening up the guts of both Canon 20Ds and Nikon D70 I could see why Canon has better amp glow performance. Nikon had the sensor on a metal block which had electronics on the backside of it as well. No doubt these electronics heat up when an image was taken.
The Canon had the sensor independent of any other electronics.
Also the Canon had several layers of metal shielding to prevent interference - again from internal electronic interference and possible external interference.
The Canon certainly seemed more sophicated in its guts and more attention to detail.
The Nikon had a handy cheap little infrared remote that I used to do long exposure images before I connected it to a computer.
A Nikon D70 is not apples to apples with a 20D Canon so needless to say the performance achievable from the 20D far rivalled the Nikon but I was quite happy with my little Nikon.
I think menus are more accessible in the Canon as well and more items could be modified but the Nikon was good too and is really more a matter of getting used to one over the other.
I used a 5D MK11 last week to image Comet Lovejoy and it was consdiderably better than my Canon 40D. The ability to go to ISO12600 versus ISO3200 and similar or better noise levels was terrific.
The 5D Mk11 also gave good colour rendition and an overall pleasing image.
But I found my 40D did better images of wildlife through my TEC110FL.
I put that down to the Bokeh effect where the backgound was more nicely blurred with the 40D. But that is a very specific use. So with my very limited experience of using a 5DMK11 for wildlife imaging I agree with the earlier posting that it may not be the perfect choice for that work.
So as previously mentioned the final use of the camera would be a mjor factor in determining which is best.
Also lenses is another factor.
I consistently read and have seen images that the Nikon 14-24 and 16-35 lenses are unrivalled and among the best ever made. Now you can get an adapter to make these work on a Canon (its about $300+) but I do not know if it affects the performance of these lenses.
For me that would be an important consideration. If you can get a 5D Mk11 to work with a Nikon 14-24 for astro work you probably are close to the perfect combo for widefield astro landscape type shots or time lapse.
The upcoming Nikon D800 may be a hard act for Canon to top. The 5D Mk111 when it finally comes out is likely to be a hot camera so keep that in mind - do you want to spend $2500 and have something that is considered outdated in 6 months time? There was a considerable jump in performance between a 20D and a 40D.
Canon seems to have been badly affected by the aftermath of the Tsunami and Thai floods. So 5DMk111 may be a while. D800 though should be soon.
Greg.
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