Best DSLR or ILC for Night Sky Imaging?

Started Nov 8, 2017 | Questions thread
camera_nerd Junior Member • Posts: 39
Re: Sony A7S

sharkmelley wrote:

If you don't mind the large pixels then the Sony A7S is the best out there in terms of sensitivity in low light for two reasons:

1) The low read noise in each (large) pixel means it has the lowest read noise per unit area of sensor than any other camera I know of.

2) The camera is very effective at keeping sensor heat low during continuous use. This gives it the lowest thermal noise per unit area of sensor than any other camera I know of. Take a look at this graph of how dark current (which translates into thermal noise) rises during continuous 5 minute exposures:

These low noise levels give you far greater flexibility when choosing shutter speed and F-ratio.

The big downside with the Sony A7S is the star eater issue but that only happens in bulb mode and you are unlikely to use bulb mode for astro-landscapes. Many people don't notice the star eater issue in any case.

The A7SII uses the same sensor but because the sensor is image stabilised it is much more difficult to conduct the heat away, so the dark current and thermal noise rise faster. Also the star eater kicks in for exposures longer than 4 seconds. The latest firmware (FW 4.0) reduces some of the star eater effects in the green channel but it still kicks in at 4seconds and above.

In addition, if you set it to video mode you can see the Milky Way, aurorae and the brighter galaxies and nebulae in real time - especially if you reduce the frame rate to the slowest setting of 4 frames/sec.



I am new to DPreview forums and have just started experimenting with astrophotography. Just got a Sony a6000 and tried it with an adapted Minolta MD 50mm f/1.7 lens. This lens has bad coma, but it let me test the a6000 till I can get a better lens.

Last night in the wash behind my condo( I live in southern Arizona 25 miles south of Tucson) I tried exposures at f/2.0, ISO1000 and ISO1600, 10 secs, 15 secs, 20 secs. The best shots were ISO1000 for 10secs. In the longer exposures the sky was gray, not black.

Also at the previous new moon I tried my Nikon D7100 but it exhibits sensor glow starting at 10 second exposures.

I would like to have a FF camera, but as a retired PC tech on a fixed income, I have a budget.  And so far my cost/benefit analysis has not favored going to FF, since I currently do not have any FF lenses.

What is the source of the Dark Current graph? That is the kind of information that I find very interesting.

Have spent a good bit of time on Photonstophotos. Great resource! Thank you Mr. Claff.

And thank you, sharkmelley for your information.


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