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Sony Nex 5N I think is well regarded as an astro cam. Small, lightweight and low noise. Its the Sony 16mp Exmor sensor that is used in many other cameras including Pentax, Nikon (since moved to different sensors).
Nikon uses a lot of Sony sensors (they are the best) for example D800, D750 but Nikon also uses a Toshiba 24mp sensor in one of their cameras (perhaps D3200?).
Nikon used to have a star eating hot pixel noise suppression algorithim that weakened faint stars in RAW images. In later models that was corrected.
Sony in their latest models do that though on exposures over 30 seconds (bulb mode).
Nex 5n can also take apps, one of which is a time lapse app which is handy.
Fuji uses the Sony Exmor 16mp sensor.
There is a rumour Sony is releasing an A7000 which has a 24mp APS sensor with WRGB filters that has the best low light performance of any camera if that is true.
Nikon D810a is a dedicated astro cam as is Canon 60Da.
I could be wrong but I have not seen particularly impressive 600D astro shots. It seems a very noisy camera.
Canon generally are best supported in this area but their sensors are aging and losing ground technically so to say all the top brands are the same is actually not true at all. Sony sensors are several generations ahead of Canon, so much so that it seems unlikely Canon will ever catch up and may continue to start using Sony sensors like they did a in a recent camera release.
But other makers like Nikon utilise the Sony sensor better than Sony themselves who are still fairly new to the high end camera game that Canon/Nikon dominate.
I'd personally go for a 2nd hand 6D if affordable. Now you'll see some good results. 60Da seemed disappointing, Nikon D810a is way too expensive, modified Sony Nex 5n would be good.
Despite the aging sensor tech Canon does make incremental advances and the weak spot in Canon sensors is shadow area noise. You can't boost shadows like you can a Sony sensor where black can be made to be light with clear detail and little noise versus a coloured noise mess with the Canon. But the Canon has all the accessories, software support, they tend to have low amp glow although that varies by model and the latest 6D is still very low noise which is quite a good result from Canon. Canon white balance though is a bit of a challenge that Canon users don't realise until they use a Sony or Fuji. I did a side by side shot Milky Way 5D3 and Sony A7r. Both on auto white balance. The Canon sky was badly brown and was going to take a lot to correct. The Sony showed perfect colour straight out of the camera, picked up green sky glow the Canon was not even showing and took no time to process. I am not 100% sure but I suspect also Sony ISO6400 is quite a bit brighter than both Nikon and Canon which must be overstating their ISO a bit. Fuji does for sure, by about a 1/3rd.
I have a half done project where I modified a Sony Nex 6. Unfortunately I have done something wrong and need to pull it apart (its probably some tiny wire I disconnected).
A modded Sony Nex 6 would be a nice imaging machine. Small, light, 16mp Sony Exmor goodness. The filters are actually easy to remove, its pulling apart the tightly packed myriad small pieces that is daunting.
Fuji X series modified would be even better.
I have a 36mp Sony a7R that I may mod if I upgrade. That could be good.
The star eating issue and lossy compression is a minor issue that is more noticeable on star trails than nightscapes or astro images. It shows when dim high contrast areas are pushed hard. I personally haven't seen the effect but would prefer Sony offer a lossless RAW like Canikon does.
Greg.
Greg.
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