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 Post subject: Night sky photography?
PostPosted: Mon Feb 14, 2011 1:47 pm 
Can someone tell me how I can take shots of the night sky and actually show the stars without the photo being pixelated? I've tried slowing the shutter speed down to 30 second exposure in the past, but I think it might need to be opened for longer, which I know I can't do normally on a camera. At the time that I tried this, I was using a Nikon d300s on a tripod.


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PostPosted: Mon Feb 14, 2011 3:59 pm 
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Joined: Sun Apr 18, 2010 12:33 pm
Posts: 443
Location: St. John's, NL, Canada
to rid of noise, lower your ISO. An ISO gain of 100 will give you virtually no noise - I suspect this is where your problem is.

Also, open your aperture as wide as it can go - this will allow more light in for the duration of your exposure.


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PostPosted: Tue Feb 15, 2011 5:30 am 
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Joined: Thu Oct 08, 2009 11:24 am
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You'll want to gather as much light as possible, and minimise noise while conserving battery life.

Therefore get as wide an aperture as you can manage and try as high an ISO as you can comfortably manage while minimising noise. Try Long Exposure Noise Reduction in camera and see how you go.

It will help if there is very little ambient or artificial light in the area as well.

If you then go down the line of photographing star trails you have a couple of options.

1 - use a remote shutter release and bulb mode to go for a longer shutter than 30 seconds - be wary that if you run in camera noise reduction this will take as long as the original exposure. Battery life can drain faster and it can take a long time to see the results

2 - take multiple exposures at 30 seconds, with one manual exposure with exactly the same settings at the end with the lens cap on. This acts as your 'dark' image and you can then use software or freeware to stack the images later


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 Post subject:
PostPosted: Tue Feb 15, 2011 4:59 pm 
How quickly will stars start to run in your shot? Streak I mean, with movement? 30sec? 15sec? 1min?


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 Post subject:
PostPosted: Tue Feb 15, 2011 7:05 pm 
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Joined: Wed Nov 18, 2009 5:23 pm
Posts: 820
Location: Boca Raton, FL, USA
How quickly stars streak depends on the focal length you are using. Generally, you can get away with a 30-40 second exposure for wider angles, as the amount of star movement in that time doesn't show too vividly. Add in some telephoto focal lengths though, and movement can start to show up very quickly, even 10 seconds or less.

Star shots will depend on general sky visibility where you are. Where I live, you might see 1-10 stars on any given night. If it's very clear, with no clouds, haze, or fog, and the temperatures are cooler, we might see a few dozen. That's it. We have horrible light pollution, poor atmospheric conditions (humidity, haze, marine layer), sea-level altitude, and are often very cloudy and with some pollution. It takes long exposures here with very high ISO to really have much of a chance to see stars in a photo - either that, or hurricanes (our best star viewing came after a hurricane in 2005 - power was knocked out across the state, so no light pollution - no cars were on the roads which were blocked with trees - no pollution from buildings and cars - no clouds or atmospheric issues as a cold front followed and the hurricane dragged everything out to sea).

I've also lived in the western US, where I was close to the high altitude deserts...out in the desert, away from any nearby city, and with clear skies and cold temps, you could see billions of stars in perfect clarity - you would need nothing more than a P&S camera and could get a photo of them by snapshot.

In general, one of the best methods to avoiding noise while still catching stars as brightly as possible, and also avoiding too much star trail movement, it to use multiple exposures. You can shoot shorter 10 second bursts, ISO1600 for better sensitivity, then stack the multiple exposures to eliminate noise across the frames. The downside is alignment - take 10 photos over a 2-4 minute period, and the stars all will have moved within the frames - you can go through the painstaking alignment of the frames using 'difference' layering, or get a star-tracking type base or pod unit that moves the camera with the stars - with those units, you can also go for much longer exposures, into the minutes, if you want.

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