Electronic shutter on the Sony A7R II

Started 4 months ago | Discussions thread
Tristimulus Veteran Member • Posts: 7,600
Re: Electronic shutter on the Sony A7R II

Igor Sotelo wrote:

Trollmannx wrote:

Guido FORRIER wrote:

I use a Sony A7R II and I shoot a lot in electronic mode but not for astro. Electronic mode does not work in bulb mode . Not a problem because is use mostly ( or I did shoot mostly when the skies were clear , a long time ago ) 5 to 10 minutes exposure . This wil not harm the shutter .


My strategy is lots of 30 sec exposures and silent shutter. Have some light pollution so using longer sub exposures do not add anything - besides some added blur by turbulence.

And no guiding needed! Grab and go. Why complicate things with looong exposures just because the mindset is stuck in the needs of the CCD era. We are into CMOS now.

Modern image sensors have very low read noise so that is a non issue in my case. Read noise is way less than the noise from the light pollution anyway. Have tried this out.

If the site is dark then go for longer sub exposures.

Below: M31 and lots of 30 sec sub exposures.

Interesting point. I have some questions.

To go over 1000mm (which will be able to do with 500mm f/4 once I get a 2x TC), does it makes sense to think about an edge HD 11” SC telescope, that’s around 2800mm f/10.

At my location the 530mm focal lenght is overkill for deep sky. Turbulent air always blur the images so my plate scale of 1.5 arc seconds per pixel cover it all.

For planetary photography, will 3x increase in FL mean much?

It will increase the focal lenght. But also the effects of the atmosphere.

I use my little telescope (106/530-5) at f/15 (3x barlow) to image the moon and the planets. With my planetary video camera which has 2.4 micron pixels the system is diffraction limited. No gain by using longer focal lenghts.

The size of the planets are pretty small, but that is the size of my sky! Happy with that.

Example - the moon and a humble 1590mm focal lenght (take a look at full size):

Since the 11” edge HD can have the secondary mirror unscrew and one can put there a Starizona Hyperstar 4 HD lens, which can 35mm in diameter image to use on something like the Sony QX1 without any obstructions or much vignetting, resulting in a 540mm f/1.9 telescope (maybe around 670mm on a APS-C sensor). Will that be useful for deep space over using 300mm 2.8 or 500mm 4.0 on full frame?

Some like the Hyperstar. Quite a few complain because collimation is difficult.

My cup of tea is small, handy and easy. Big dreams are easily crushed. Small dreams remain robust and last forever.

Have a small astro shed. Am into business within 10 minutes including taking the flats. Unpacking takes hardly 5 minutes. That is astronomy heaven to me (ignoring the fact that the weather is usually lousy here).

Finally, does it makes sense to pickup some very small CMOS sensors to gain 5x FL in the case of Celestron’s 10MP sensor or around 7x for some ZWO 2.1MP sensors.

The smaller image sensors do not extend the focal lenght of the telescope. They just crop the image. Plate scale is determined by the actual focal lenght anyway.

Make the system diffraction limited. No more. That is about f/15 for 2.4 micron pixels.

Longer focal lenghts are a waste. Why go for empty magnification just to get a larger but more blurry image with absolutely no added detail?

Will I be able to get good photos of Uranus or Neptune? Can one do the same by just cropping from a 42MP A7R II sensor and avoid focusing problems?

Shorter focal lenghts and tiny pixels have the upper hand. Why image at f/40 when f/15 can do the trick? And why use a camera not quite up to the job at hand when a small video camera will easily nail it?

The end result depends upon the atmospheric conditions at your site. The atmosphere, not the telescope, is usually the limiting factor when using mid sized or large telescopes. We can not beat nature.


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