Help with star trails

[usfpaul82]

Hello,

I would like to try my luck with some star trail shots. I have done research and now its time to get hands on (weather permitting of course) but wanted to know what you guys think is the best lens for this out of the ones I have. I am shooting with myt d50 on bulb mode. My lenses are the kits lenses (18-55 vr and 70-200vr), 50mm 1.8, and my sigma 105mm 2.8 macro. What do you guys think? Thanks

 

[swjim]

Doug (Beerguy) has a beautiful shot with a nice writeup here: http://www.binaryemulsion.com/wordpress/2009/05/26/starry-night/

 

[BlueCorn]

Thanks swjim!

Choose the lens based on the way you want to frame the scene. For star trails you want to shoot on a moonless night. To get decent trailing you need to have the lens open for at least 15 minutes. Focusing in low light can be tricky. One way around that is to setup your scene before it's totally dark and just wait.

Another method that folks use is setting the camera to a 30 second exposure and locking the remote release. So the camera shoots a series of 30 second exposures and they you combine them, as layers, in Photoshop. There are also some freeware programs for doing this. It's called "stacking."

To figure out your exposure I'd start with something around f/4, ISO 400 and 20 minutes. You'll need to adjust from there. Remember that one "stop" is a doubling of exposure so if you find that you need more light you can either go to f/2.8, ISO 800 or 40 minutes. With your camera you probably don't want to go above ISO 400.

Make sure that your battery completely charged and turn on in camera noise reduction. The way it works is that the noise reduction frame takes as long as the original exposure; i.e. if you take a 20 minute exposure it'll be 40 minutes before you see it on the LCD. Some cameras allow you to continue to shoot during noise reduction but I'd be surprises if the D50 does.

Cheers

 

[TWallace]

I have some experience in this area as I have the same camera and some of the same lenses. First, forget the 18-55. It doesn't have a hard infinity focus, which makes it exceedingly difficult to focus on stars. The 50mm 1.8 is an awesome lens and does have a hard infinity focus stop (at least it does if it's the same model as mine). Only problem is not very wide. You probably want something 35mm or wider, but I'd definitely try it with the 50mm first to see how you like it and also for practice. If you don't already have one, get the wireless remote for the D50 for around $15. That will let you do exposures longer than 30 seconds without bumping the camera to start/stop it.

I recently upgraded to the D90. One of the reasons I upgraded was that a remote was available for the D90 that allows me to set exposures longer than 30 seconds without having to time it myself. Can't do that on a D50. The same remote also has an intervalometer for time lapse photography which I'm also into.

I ended up buying an old 24mm manual focus AIS mount lens for $80 used (they sell for over $300 new). To me, this lens is only good for astrophotography as the AIS mount means it will not meter on a D50. Coupled with manual focus, it's just a huge pain to use in any other situations. But with astrophotography, you use infinity focus and manual mode anyway, so those aren't limitations in this instance. Nikon makes several fantasticly sharp lenses like 20, 24 and 28mm. I'd search Craigslist for a used one and see if you can score a good deal. They tend to cost more on eBay than Craigslist in my experience.

I agree with beerguy on sticking with low ISO. 1600 is horrible on the D50 (and probably on most other cameras, too). 800 is so so, 400 and 200 are great.

If you're in the city, be prepared for disappointment with star photos. City light pollution is ugly and hard to avoid. All my photos come out with the sky looking orange/brown. You have to head outside the city to avoid this.

When you do try it out, post some photos here.

 

[usfpaul82]

thanks for the tips guys. It has been raining for days here so I have not had the chance to go out. I'm not really in the city so I hope i will be ok. I'll try with the 50mm and post some pics whenever I can get them done.

 

[IPT]

as for focusing on infinity at night I have few solutions from shooting the aurora. All my wide angle fixed focal length lenses have the barel marked so I just use my head lamp to set it to infinity and double check before I expose. If there is any moon you can usually focus off that. Sometime you may need a distant tree infront of it. The focusing system is looking for an edge to focus off. LAstly, if you're near your car just tunr on the head lights and focus on something (> than 30' I think) and you should be good to go.

 

[t5Nitro]

So it doesn't matter how you do it? It'll never overexpose a picture? Seems like 25 minutes or 40 minutes is a long time. Just use a lower ISO to avoid grain?

 

[BlueCorn]

<a href=showthread.php?s=&postid=15291102#post15291102 target=_blank>Originally posted</a> by t5Nitro
So it doesn't matter how you do it? It'll never overexpose a picture? Seems like 25 minutes or 40 minutes is a long time. Just use a lower ISO to avoid grain?

It does matter but you're dealing with very low light. Going from 20 minutes to 40 minutes is only 1 stop.

 

[t5Nitro]

So how do you guess how long to leave it open for to get the right exposure?

 

[BlueCorn]

Guessing means that you pick an exposure and try it. For me, 20 minutes, on a moonless night at ISO 400 and f/4 is a good starting point.

 

[vbjimmie]

Read an article on star trails last month. Was a lot easier with film bodies....but here is the link.


http://www.moosepeterson.com/digitaldarkroom/lessons/lights_of_the_Heavens.pdf

 

[TWallace]

Here's a decent attempt I made last night.

I think it's a little underexposed. It's a combination of 279 images. Each one was exposed for 22 seconds at f5.6, ISO 250 using a 24mm f2.8 AIS manual focus lens. It has not been cropped, so what you see is the full viewing angle of a 24mm lens on a crop sensor (D90 in this case) camera.

I may try again tonight using fewer and longer exposures. I originally tried an hour and a half exposure the previous night using ISO L1.0 (which I think is 100). It looked horrible. Totally filled with noise. That's why I decided to try several short exposures and then combining them in Photoshop.

In case you don't know, an easy way to combine them in Photoshop is to use your first image as the bottom layer, copy/paste the second image onto that as the second layer and choose "Lighten" as the layer mode. Repeat for all images and you'll get your star trails. However, if you shoot RAW like I do, this is very time consuming for this many images (which is one reason you may want to shoot longer exposures to reduce the image count). You can automate this with Photoshop using File -> Scripts -> Image Processor. I created an action that gaussian blurs the image at 0.2 pixels (helps reduce noise), copies the image, closes it, pastes it on top of my base image, selects "Lighten" as the layer mode and then merges it down into one layer. Then it repeats for the rest of the images.

Since your D50 doesn't have an intervalometer and you probably don't want to stand next to your tripod clicking the remote over and over for an hour, there is a trick I read about to make it easier. Take a rubber band and a pencil eraser with you. Set the camera to 30 second exposure. Wrap the rubber band around the right side of the camera and over the shutter button. Place the pencil eraser between the rubber band and the shutter button. This will hold the shutter down, causing the camera to repeatedly shoot 30 second exposures until you remove the rubber band (or the battery dies, or the SD card fills up). I have read that this doesn't create enough pressure to press the button, but it does create enough to hold it down if it's already down.