# D90 shutter speed



## tresguey (Apr 18, 2009)

Tonight I have been taking pictures of the stars. I want long trails and my shutter speed only goes out to 30 seconds. Anyone know how to make this longer?


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## prodigy2k7 (Apr 18, 2009)

Do you have a bulb move somewhere, like after 30 seconds does it says bulb? I have a different camera but im assuming your camera has it ;x

If you are in bulb, the shutter will stay open as long as you hold the shutter button. (better to be used with a remote)


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## DavidElliot (Apr 18, 2009)

you can also try stacking images for star trails

Stacking star trails: tips and techniques


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## tresguey (Apr 18, 2009)

Thanks for reminding me of the bulb setting. I read my manual but that part slipped my mind. And I am new to this photography thing.

That stacked link is pretty cool


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## Katier (Apr 18, 2009)

Be carefull going for overly long exposures. Digital sensors heat up as they record the image and long exposures can get very noisy. The idea of combining trails is a good one and reduces the chance of noise.


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## Dwig (Apr 18, 2009)

Katier said:


> ...The idea of combining trails is a good one and reduces the chance of noise.



Even if you use Bulb to get longer than 30sec exposures, stacking is a good trick. By reducing the individual exposure times you somewhat reduce the noise in each indificual image. A bigger improvement comes from the fact that the noise pattern, being random, doesn't match image to image, and is thus suppressed in the assembly while the real image data, being aligned, is reinforced.

BTW, the Earth spins at 15 degrees per hour. To get a star trail with a small 5 degree arc you will need a 20 minute exposure (or 20 stacked 1 minute exposures). Longer arcs require longer expousres. Plan you total exposure time accordingly.


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