Best DSLR or ILC for Night Sky Imaging?

Started Nov 8, 2017 | Questions thread
sharkmelley Senior Member • Posts: 2,152
Re: Best DSLR or ILC for Night Sky Imaging?

RustierOne wrote:

sharkmelley wrote:

RustierOne wrote:

My question:

The star eater began kicking in at Bulb = 30 seconds. But a later firmware upgrade lowered that to a shorter exposure. Do you know what the limit is on current new A7S cameras?

The A7S star eater still only happens in bulb mode. So all exposures longer than 30sec are affected (because they have to be done in bulb mode) as well as short exposures done in bulb mode.

The expansion of the star eater issue to all exposures 4sec and longer was done only to the Mark 2 models i.e. the image stabilised models, because of the complaints about increased noise in long exposures compared to the Mark 1 models. The increased noise was probably thermal noise caused by the fact that the sensor has to free to move around and so it can no longer be in contact with heat sinks.

I can't see Sony ever going back to fixed sensors because photographers love image stabilisation, so the Sony A7S will probably remain the best ever Sony camera for low thermal noise.

Thanks for your informative reply, Mark. In your opinion, when star-eater is not initiated, are the Soy A7S cameras worthwhile for astrophotography. Seems like you reported some manipulation of RAW files in a way you didn't like. I know this has been discussed at length. But my interest in a replacement camera still points toward the A7S.

There is another A7S issue that won't be noticed when doing astro landscapes but will start to become noticeable when performing deep-sky astrophotography where you need to perform vignetting corrections, skyglow subtraction and stretching. The Sony A7S appears to perform a digital scaling of the raw data which leads to regular gaps (or dips) in the histogram and produces coloured concentric rings. It's all explained here:

However this can be prevented by shooting with a high enough ISO to make sure the histogram is approximately in the centre of the back of camera display and not over to the left.  This strategy does of course eat into the available dynamic range.

The Sony A7S remains my main deep sky astrophotography camera - I just have to restrict exposures to 30seconds to avoid star eater and expose well to the right to avoid concentric coloured bands.


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