Understanding ISO, shutter speed and F stop

Started May 13, 2012 | Discussions thread
Graystar
Veteran MemberPosts: 8,373
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Re: Does that buy you anything?
In reply to HowardinOregon, May 14, 2012

HowardinOregon wrote:

3. ...My thinking is lower iso=better noise reduction.

And that's correct. There's no valid reason for increasing ISO beyond the base ISO of the camera. Like I said in my other post, I actually go one step below base ISO. However, that's not true for all types of astrophotography. There are some techniques where high ISO is used.

4. Thanks for the informtion about an equitorial. What other practical uses does such a device have (moon shots are relatively infrequent)?

Equatorial mounts are used for astronomy. When you're viewing objects in the sky, it helps to have an equatorial with a clock drive. I have a 1500mm telescope and at the highest magnification you can see objects moving across the field of view. The clock drive holds the image steady by rotating the mount opposite the rotation of the earth.

For serious high-magnification shots of the moon you actually need a computer driven mount. An equatorial with a simple clock drive is great for viewing objects, but the moon is in orbit around the earth and so its rate of movement is different than other objects in the sky. This is important for long-exposure shots as well, such as a lunar eclipse shots.

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