Nikon D90 Ruined Image Sensor

Started Aug 18, 2012 | Discussions thread
Mr Physics
Mr Physics Contributing Member • Posts: 716
Re: Why the obsession with high ISO?

nfpotter wrote:

rjnicko wrote:

I used high ISO when doing my Astro photography

Why? You shouldn't be, unless you need a fast shutter speed, for some weird reason.

Otherwise, you should be shooting at base ISO, with long shutter speeds, tripod, remote release or time mode and either mirror-up mode or exposure delay mode on.

Each celestial object is in constant motion across the night skies. Our reference frame, the Earth, is rotating always (we hope) and each of the points of light in the sky are rotating with it. If I'm doing an image of the moon with a 300mm or 500mm lens, it'll be in and out of my field of view in the time it takes to smoke a cigarette. My "back of the envelope" calculation: 4200pixels/300secs= 14 pixels movement per second. If you want any kind of sharpness in your astro-photos you'll need 1/15s shutter speed or a sophisticated telescopic tripod mount. It'll only get worse with greater focal lengths.

Best regards,

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