stars >>> big dots

[Pappy]

Tonight I tried a shot of the stars from my backyard. The sky was a little hazy but not too bad. Could see lots of starts plainly. Used 18-55mm lens set at 18mm. Tried lowest f stop (widest aperture). Tried highest ISO (3200). Shutter opened for 30 seconds. Camera on tripod. Used wireless remote for shutter. Thus, no camera shake. Pictures came out grainy (from 3200 ISO, I presume) and stars were big round dots, not points of light. What did I do wrong?

[OsmosisStudios]

You overexposed the ever-loving crap out of the Haze.

What happened is that, because your shutter was open so long, you had alot of light from the stars hitting the haze, which was then reflected into the camera. By itself that probably wouldnt be a massive issue, but with a long shutterspeed, wide aperture and high ISO, youre begging for a big old fashioned blowout.

When doing stars you should have settings as follows:
Aperture: f/16 (general rule, but its about right)
ISO: As low as possible. Probably 100.
Shutterspeed: BULB. This allows you to set the shutterspeed into the minutes, hours, etc.

Now, BULB actually allows you to keep the shutter open for as long as youre holding the shutter release down. In this case, a remote works well. You didnt mention whether you were shooting NIkon or Canon, but both have wireless remotes for dirt cheap ($25, first party). With the Nikon (and presumably canon), you press the remote once to open and once to close: you can have HOURS in between, provided the camera is being fed with power from either a battery of an AC adapter.

The other thing you'll need is a cristal clear night. With long exposure, any haze you can see will be multiplied by a very high factor. You need it to be clear. The other thing you'll need is a low light-pollution area. Shooting in town isnt an option: youre gonna need to get waaaay out there

[Pappy]

Thanks for the advice! As you can tell, I'm a novice. I really appreciate your help.

[OsmosisStudios]

Originally Posted by Pappy

Thanks for the advice! As you can tell, I'm a novice. I really appreciate your help.

No problem. That;s what we're here for.

There are alot of things that most people dont shoot on a regular basis and, when they try, they get some pretty wonky results. Youve obviously experienced this. I have too, in the past.

Most weird things ive seen revolve around night-shooting too.

[Egger]

Also, maybe the auto focus couldn't focus on the stars so the round circles were bokeh(http://en.wikipedia.org/wiki/Bokeh). It may be helpful to switch to manual focus and put the distance on infinite.

[navcom]

Originally Posted by OsmosisStudios

You didnt mention whether you were shooting NIkon or Canon, but both have wireless remotes for dirt cheap ($25, first party). With the Nikon (and presumably canon), you press the remote once to open and once to close: you can have HOURS in between, provided the camera is being fed with power from either a battery of an AC adapter.

Hmmm...you know there are other camera brands out there besides Nikon and Canon that do just fine too. And they even come with remotes and AC adapters!

Had to say that!

Otherwise, advice on haze and exposure is right. I assume the OP wants to do star trail photos. A 30 second exposure will not produce star trails, but just star "dots", as stated. You need very long exposures to produce long trails. With a digital camera, it is better (though not required) to do several shots of about 10 minutes a piece and then combine them together.

A free program that is perfect for this can be downloaded at www.startrails.de.

[dcclark]

Since we're on the topic of star trails...

First, depending on your camera, 10 minute exposures could cause some bad amp noise. On my D40, I have been attempting 3 minute exposures, which are just about the limit.

Second, does anyone know of a free stacking program for Mac OS X? I have used PhotoAcute, but it's just a demo version of a for-pay program, and it really has a terrible interface. Also, it watermarks my photos. Any ideas?

[navcom]

Originally Posted by dcclark

Since we're on the topic of star trails...

First, depending on your camera, 10 minute exposures could cause some bad amp noise. On my D40, I have been attempting 3 minute exposures, which are just about the limit.

Second, does anyone know of a free stacking program for Mac OS X? I have used PhotoAcute, but it's just a demo version of a for-pay program, and it really has a terrible interface. Also, it watermarks my photos. Any ideas?

You are right. I suggested the 10-minute interval precisely because of sensor noise. 10 is about the max most cameras will be able to handle without undue noise (depending on the outside air temp).

Many cameras have noise reduction features. These usually compensate for generated noise by taking a second photo with the shutter closed (black) and using it to remove the noise from the initial exposure. This usually means that when you are done taking your long exposure, the shutter will close and the camera will sit there for long time taking a second exposure similar in lenth to the first. If you are taking several in succession, waiting for this feature to finish will result in gaps in your star trails.

For this reason, if your camera has a noise reduction feature that responds this way, turn off the noise reduction completely. After all your exposures are finished, THEN take a black photo manually. The star trails program I suggested allows you to include a "black" frame for just this reason...noise reduction.

I love star trail photos! I think it's the relaxing nature of taking them that is so wonderful!