Startrail Issues

[andrew_jacobson3]

<p>Hello All,<br>

First off, sorry if this is in the wrong forum, but it seemed to be the only one that fit...</p>

<p>I am working on an independent study project for school this semester. I decided to improve my skills in night-time photography (Using long shutter speeds, creative lighting, etc.) Maybe not the best choice for a class out of Minnesota in the middle of the coldest winter that we've had in a long time, but.. That's a different issue..</p>

<p>My most recent photo was is an attempt at Star Trails. I set my camera up on a tripod and, using a remote, set it to take 30" long photos for about an hour and a half. The result:</p>

<p><img src="http://i1229.photobucket.com/albums/ee461/wolfeye_15/Startrails_zpsdc9f1d22.jpg" alt="" width="682" height="1024" /></p>

<p>I am not done with the editing process of course.. I want to eliminate the airplane lines at the top and just above the treeline, as well as get rid of the obnoxious lights created be the cars driving past and brighten the image all together, but the big issue that I have with this photo is with the stars themselves... </p>

<p>The lines are almost broken in spots. I am wondering if anyone knows why this might have happened.. If there is anything I can do about it now... And what I can do in the future to prevent this from happening again...</p>

<p>Thank you,<br>

Andy</p>

 

[bobatkins]

<p>"<em>The lines are almost broken in spots</em>"</p>

<p>If it's regular, possibly because there is a gap between your consecutive 30 second exposures? It's hard to tell from your posted image because it too small to see any details in the trails. Maybe post a crop from that image at 100%.</p>

<p>There are lots of "jaggies" in the posted image trails, presumably because of the downsizing. What does the full size image look like? If you want to downsize you might want to use something like a weighted average downsizing algorithm, though there's really no way to get smooth diagonal lines in a downsized image if you're looking at it closely. That's just the way that digital is. If the lines approach the width of a single pixel, anything but horizontal and vertical lines will not be smooth.</p>

<p>With circumpolar shots you can use a radial (spin) blur centered on the north celestial pole. That will average out the gaps on the original image somewhat.</p>

<p>You can also stack multiple images to remove the exposure gaps, though obviously that's tricky with moving stars and long exposures. You can also try the "startrails" software.</p>

<p>Here's a 100% crop from some similar images I've shot. Multiple 30 second exposures.</p><div></div>

[andrew_jacobson3]

<p>Gotcha. Here is one cropped in</p>

<p><img src="http://i1229.photobucket.com/albums/ee461/wolfeye_15/Startrails1_zps34d2e3dc.jpg" alt="" width="682" height="1024" /></p>

[bobatkins]

<p>Looking at that I'd maybe also question the stability of your tripod. Looks like more than just "jaggies" to me.</p>

<p>What camera? How long between consecutive exposures? I presume you have background subtraction turned off (no long exposure noise reduction in the camera)?</p>

[andrew_jacobson3]

<p>I am shooting with a Rebel T3 (the 18-35mm kit lens) and I had those all turned off. Could the cold weather have an influence here?</p>

 

[bobatkins]

<p>I doubt it. In fact cold weather may marginally lower image noise. I presume you also had image stabilization turned off if your lens has it (some 18-55 lenses do, some don't).</p>

<p>It looks like you have some sort of random position variation between shots. Either something is moving or you're not stacking the images well.

<p>How are you adding the multiple 30" images together?</p>

<p> </p>

[pics]

<p>It definitely looks like you have some camera shake going on. Make sure everything is locked down tight. If your tripod has a hook on the bottom of the center column, try hanging your camera bag (or something heavy) to add some stability and buffer against any vibrations. Also, once you have the focus set, turn off the auto focus if you didn't already. Your camera may be hunting for focus before each exposure causing movement and it may also not be focusing correctly every time. (common during night shots). </p>

[andrew_jacobson3]

<p>Ok, I'll have to try the tripod thing.. Auto stabilization was off (I don't really ever use that thing...). I loaded them into Photoshop using Bridge and simply set the layer option on each of them to lighten so they would all come through</p>

[pbizarro]

<p>A solid tripod is indeed a requirement. Also how are you taking the consecutive 30" images? A good way to do it is to set the camera to Continuous drive in Bulb mode, and then just lock the cable release. Then there is no interval between consecutive shots.<br>

One other thing is to shoot some dark frames (similar exposures but with the lens cap on). You can later use these in specific stacking softwares. I can greatly recommend StarStax as a very nice and easy stacking programme to create star trails.</p>

[zelph_young]

<p>If you want unbroken star trails, use film. All the rest about solid tripod and whatnot still apply.</p>

[Glenn McCreery]

<blockquote>

<p>Zelph is right. Haul your old SLR (without the D) out of the closet and dust it off. Extremely long exposures are one of the few areas that film still out preforms digital.</p>

</blockquote>