Star Trails: Two Questions

[brian_winshell]

<p>I am going to Acadia National Park in two weeks and I plan on making my first attempts at shooting star trails. I have a D200, adequate lenses, and just purchased <a href="http://www.amazon.com/gp/product/B003VIH91G/ref=oss_product">an intervalometer</a>. I have read <a href="http://www.moosepeterson.com/digitaldarkroom/lessons/lights_of_the_Heavens.pdf">this article by Moose Peterson</a> in preparation and I alomst understand everything I need to know and have a good idea of how toapproach this. I will shoot a dark frame with my lens cap on and set the intervalometer to take 30sec exposures with 1sec gaps in between. I will also be using the <a href="http://www.startrails.de/html/software.html">startrails.de application</a> to combine the exposures. I know some might suggest that I practice first but I don't have time to practice this before I go, so, this trip will be my first experiment. A successful first attempt would be nice but it's not vital to my happiness :) So here are my two questions:</p>

<p>1) I read that the dark frame will subtract the noise from the final image. However, should I still have long exposure noise reduction turned on while making my exposures?</p>

<p>2) The Moose Peterson article suggests 4 minute exposures with 1sec pauses, however, I have read in many places that 30sec exposures with 1 sec pauses will produce great results. How badly do the 1sec pauses effect the final image? Should any of my attempts be successful I will most likely make a large (20x30) print and I wouldn't want the trails to look like morse code.</p>

<p>Thanks for your time and attention!</p>

[acbeddoe]

<p>A one second pause is negligible. There are 86,400 seconds in a day; the sky will have rotated 0.004167 degrees (15 arcseconds) in that time.</p>

[karl_lehmann]

<p>"...should I still have long exposure noise reduction turned on while making my exposures?"</p>

<p>Definitely not. If you do that you will end up with extra 30 second gaps between exposures, which will turn your trails into a series of dashes. Your dark frame replaces long exposure noise reduction (which is really the same thing).</p>

[Christa Binder]

<p>I have tried thirty second exposures and the trails did not show up in my photographs except when my ISO was at 800 or 1200, also my lens was set at F4.</p>

[brian_winshell]

<p>Great, so I will keep noise reduction off. </p>

<p>Christa what were the sky conditions and focal length you were working with. I have seen numerous threads stating that a wide focal length, f/2.8-f/4 , ISO 100 works just fine. Also there is little light pollution in Acadia. So the stars should be plenty bright.</p>

[unclebuddha]

<p>I don't know what an intervalometer is used for but if you set your camera to "motor drive" and your shutter speed to 30 seconds and aperture to wide open and your ISO to 800 (with a first dark frame as stated) then you'll be fine. Make sure you turn off any VC if you have it (don't ask me how I know). Using a remote shutter release lock the trigger open and the camera will fire 30 second exposures for as long as the battery lasts or until the card is full. I shoot medium JPEGs too. Try to have something in the foreground (you knew this). Even if the moon is full, the picture will stun you. Have fun!</p>

 

[brian_winshell]

<p>Have you seen ISO 800 on a D200? That would be way too noisy I'm sure, especially with noise reduction turned off. Is there anyone out there with extensive experience shooting star trails that might argue using such a high ISO. Every time I google star trails, I find numerous sites saying ISO100-200 and f/2.8-4.0 is sufficient to capture the trails using 30sec exposures. If I have to go up to ISO 800 I might as well forget making any decent size prints. Can the dark frame really take care of the noise on a D200 at ISO 800? </p>

[craig_meddaugh]

<p>Most of what we think of as "noise" is random, so when you start stacking your exposures, even at high ISOs, you will find that it disappears as it is averaged out. You only need the dark frame to eliminate amp glow (thermal noise), which is non-random. </p>

<p>As to your exposure settings, there are lots of ways to skin this cat.</p>

<p>1 second pauses are irrelevant as the stars will move a neglible amount during that time. However, if you use long exposure noise reduction, that will make an extra dark frame exposure for every shot, so if you are taking 30 second images, you will have 30 second gaps in your star trails. That may be material. Again, noise is going to average out so don't worry about long exposure noise reduction. </p>

[Christa Binder]

<p>I just went back to those pictures and my lens was at 12mm @5.6, and ISO100, the only way to get anything to show up in them is to adjust curves and brightness and that just makes them look terrible and really noisy, they are just to underexposed to fix. Stacking the trails does help eliminate the noise. It was clear outside that night and I live in a area dark enough to see the milky way, (not all of the details, but you can still make it out.) The software that you are using is really good, I have used it a few times, but now I use photoshop. I think it is best to use an ISO of 200 or 400, with a time of around four minutes each, this has worked better for me than any other settings. Plus setting your exposure to a time of four minutes each will let more light in and the fainter stars will show up better in your photographs. If you are going to use a foreground object in your photo, unless you want it to be black, you could set up your camera before it gets completely dark and take an extra exposure for your foreground. Another thing to think about is to set your focus on infiniti, focusing in the dark can be nearly impossible. Do not rely on your cameras lcd to tell you if you got your exposure right, use the histogram instead. When there is low ambient light outside your lcd is going to seem brighter. </p>

[Christa Binder]

<p>I forgot to mention that I usually use AV4.0 of AV5.6, sorry about that. Have you seen any Startrails photos by Harold Davis? IMO he has some of the best. If you would like to see them you can visit this site <a href="http://www.digitalnight.us">www.digitalnight.us</a></p>

[steven_f1]

<p>Iso 100 should work fine. However before you start the process do a seperate 30 second test photo. If you don't like theresults try a higher iso. Once your test photo looks OK take your dark frame and then use your remote to lock down the shutter. I would stay with 30 second exposures. The noise on my camera seems to get much worse when my exposures get longer then a few minutes. To get as much light through the lens as possible us a wide aperture. If you wanted pin point stares without star trails I would recomment stopping down a little to get a sharper image. However with star trails I don't think that makes that much difference. The day before you attempt this mark the infinity focus on your lens. Focusing using the viewfinder will be almost impossible. also make sure your battery is fully charged. It will probably be dead after about 90minutes. </p>

[unclebuddha]

<p>Okay, so maybe ISO 800 would be too much on your Nikon. I shoot with Canon so I dunno! I would NOT shoot anything more than 30 seconds since I fear "hot pixels" from longer exposures. Wide open, focus at inf, 30 secs, lock her open and let her rip. If you want the items in the foreground slightly lit, try a big candle or something set up out of view in the foreground. I'll post up my latest effort when I have the time. Good luck.</p>

[brien_szabo]

<p>Sounds like a lot of work. I understand that noise can be an issue but I've also experienced where the lack of humidity can also help keep noise reduction down. This shot is 40 minutes in length, f/4.5 ISO 200. I've had many successful images that I've printed 13X19 without all that interval work. But hey.., whatever you believe will work for you.</p><div></div>

[brian_winshell]

<p>Hi again! I am back from Acadia National Park and I thoughI would share the results of my first attempt at star trails. I personally don't like when people ask for advice and then don't follow up after that advice has been applied. Taken with Nikon D200 and Tamron 17-50mm f/2.8 VC. 17mm, f/2.8, ISO200, 30sec exposures stacked with star trails.de software, tungsten white balance, foreground painted with mag lite, Exposure slightly boosted in Adobe Lightroom. Anyway, thanks for all the replies!<img src="http://www.brianwinshell.com/wp-content/uploads/2010/08/Startrails-1024x685.jpg" alt="" /></p>

<p> </p>

[unclebuddha]

<p>Brian,<br>

Very nice work. You must have had a very dark sky.<br>

Mark</p>

[brian_winshell]

<p>thx :) New Moon actually</p>

[brian_winshell]

<p>I am starting to like it better with the trees silhouetted. Thoughts?<br>

<img src="http://www.brianwinshell.com/wp-content/uploads/2010/09/Startrails2.jpg" alt="" width="1600" height="1071" /></p>

[jwallphoto]

<p>Is the stuttering in the trails a jpeg artifact? I like the silhouette version best. Some good ideas in the comments. I need to give it a try sometime.</p>

[hydrologic]

<p>Silhouettes for the win!<br>

@John W. - I, too, was compelled in this thread. I will be testing this, as well.</p>