Nice shot but you have some star trails showing in the larger image.
You might want to open up well beyond f/8 to shorten your exposure time.
The exposure of extended objects (sky, nebulae, ground, sea) will
respond as you expect by opening a stop. Stars, however, are point
sources and do not respond to focal ratio like extended objects. They
respond to physical aperture but not to focal ratio. As long as you're
using the same lens opening up a stop or two or three will have the
expected effect since going to f/4, for example, will also increase the
physical aperture of the lens. But f/4 on a 50mm lens will have much
less exposure effect on stars than f/4 on a 100mm lens since the
physical aperture on the 100mm lens will be twice that on a 50mm lens.
Just some oddities for astro work. I suspect that whatever lens you're
using will perform just fine for this kind of work when it's wide open.
But I don't know that for sure.
Chuck Norcutt
On 2/10/2013 9:07 PM, Bob Whitmire wrote:
> My first attempt at astrophotography. Inadvertent, as in unintended,
> maybe even accidental. I was shooting 180 degrees off a boring sunset
> and just when I was about to pack it in, the sky started to get
> interesting again. So I deployed the tripod, set up and just hung out
> for a while, trying to keep the ISO at 100 and lengthening the time.
> Then stars started to pop out. Couldn't tell from chimping if I was
> getting them. Couldn't see them in the viewfinder. Too bad I missed
> one of Orion's. I thought I had it, but obviously I didn't. Still, it
> was fun. And now I have something new to keep me out after dark.
>
> http://zone-10.com/tope2/main.php?g2_itemId=2218
>
> --Bob
>
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