Another APS-C astrophotography contender?

[The Thing]

I read on the AstroPhotograhpyTool forum messages that APT will soon support Sony cameras. This appears to be driven by the mirrorless a6000. It looks good, 24mp Exmoor sensor and a body can be had for £369.

[RobertM]

Bout time !

[Carole]

I find the support from Ivo (APT) to be excellent, and he's always updating and fixing and improving.  I sometimes use it for my CCD cameras so I can use the dithering.

Carole

[RobertM]

I find the support from Ivo (APT) to be excellent, and he's always updating and fixing and improving.  I sometimes use it for my CCD cameras so I can use the dithering.

Carole

Beep Beep ! Hijack alert !

[MarkS]

In principle, I think mirrorless cameras with sensitive sensors are definitely the way forward for "DSLR" imaging. 

However, before considering it as a real contender, I would have the following questions:

1) The A6000 camera is only 12 bit (again!), not 14 bit.  Why does Sony do this?  For instance, the Sony sensor used in the Nikon 7000 is the same as in the Sony NEX-5N.  The Nikon was 14 bit but Sony's own sensor in Sony's own camera was crippled to 12 bit.  The mind boggles. 

2) Does the camera produce lossless RAW images?

3) Does the camera clip the pixel values in calibration darks?  I think every manufacturer except Canon clips the values which is why Canons are so competent for deep sky astro-imaging.  However there is now a hack for Nikons to produce the unclipped data.  Does Sony have a hack?

4) How easy is it to mod for H-alpha sensitivity?

5) Do the pixels devoted to phase detection focusing cause artifacts or star destruction? I've no idea on this point but I'm interested to know!

6) What is the dark current (thermal noise)?  Exmor sensors are generally very good in this respect.

On the plus side, it would appear to be a very sensitive sensor with very low read noise at a very reasonable price.

Mark

[Carole]

Beep Beep ! Hijack alert !

Cobblers, it's relevant to the fact that IVO keeps updating the software, thus now the addition of Sony.  Perhaps I just worded it wrongly. 

Carole

[RobertM]

I will do some tests on my Sony when I get a chance and try to find answers to some of those questions.  One major gain for me is the complete absence of shadows from the mirror box.  Another potential game changer is in camera apps (if they ever release the API).

Yes Canons are 14 bit but if you use them at ISO 800 (550D) then there may be less than 12bits worth of values (<4096).  That situation will get worse at higher ISO values.  I'm not defending the use of 12 bit but just highlighting that theres not that much difference at higher ISO values.  Where lower ISOs can be used then yes that extra resolution helps.

Robert

[MarkS]

I will do some tests on my Sony when I get a chance and try to find answers to some of those questions. 

Aha - so that's what you've been keeping quiet about!

Looking forward to seeing what you conclude.

Mark

[MarkS]

Regarding the phase detection pixels for focusing, you might find this thread interesting:
http://www.cloudynights.com/topic/413422-examining-the-650dt4i-hybrid-cmos-af-pixels/

It's a 650D but I'm sure the principle is the same.  To be honest, I don't think you'll ever notice it in your final stack but it's good to be aware.

Mark

[MarkS]

I'm actually very tempted by this camera.  The sensor is a big jump from the Canon 350D-700D range of camera and it will give my astrophotography a new lease of life until APS-C or full frame size mono cooled cameras start appearing with Exmor sensors.  That's a hint to Sony - please, please start producing mono versions of your excellent sensors and sell them to Starlight Xpress, Atik, QHY, Moravian, SBIG, FLI, Apogee for building the next generation of budget astro-cameras.

The only outstanding question is ease of modification which I'm assuming will be something like this:
http://www.dpreview.com/articles/2352853254/sony-a7r-teardown-roger-cicala-lensrentals-gets-his-hands-dirty

Mark

[RobertM]

I don't think you need more small pixels but it would be a good camera none the less depending on focal length.  I understand astro modification would be very easy but then you do invalidate the warranty.  Personally I think the 12 MP S version is the camera to have though apart from hand held I've not got more than a few jittery images out of my Sony.

http://www.dpreview.com/forums/post/53993974

Robert