Star Trails...just want to be sure...

[lextalionis]

Hey gang,

Our cub scout pack will be camping out at Enchanted Rock this weekend. I plan to do my first star trail shot. I've read some on this but I'd just like to check in with you all who have experience.

First, does anyone have an ~ battery life of a Canon 30D battery with shutter open and IS turned off on the lens? I would like to get at least a 40 min shot.

1. camera on tripod pointing towards the north star
2. iso 200, f/8, manual, using shutter-release cable in bulb lock position, focus to infinity, no lens hood (or lens hood?)
3. ensure no moving lights, cars etc. in path
4. at 40mins release bulb lock

Sound good?
Thanks,
Roy

[HFMarshburnJR]

Roy -

Try this approach - it has worked well for me

1. Camera on a tripod,cable release, NR off, no lens hood
2. Try and put a point of interest in your foreground between you and the North Star
3. ISO 200, Lens wide open + 1 stop (f2.8 lens set to aperature of F4)
4. Put your focus mode to manual and set your focus to infinity
5. Instead of one 40 minute exposure, take 10-15 4 minute exposures and stack them using your favorite post processing software (when layering, use the "lighten" mode). This will help cut down on noise, hot pixels, etc. At the end , put your lens cap on and take one more 4 minute exposure with the same camera settings. This is for black frame subtraction of noise from your stacked image. Copy this layer onto the top of the stack and use the "difference" blend mode.
6. There will be a new moon on Saturday night, so you might think of using your flashlight or other light source to "paint" the foreground. Otherwise, your foreground element will just be a silhouette - which ain't always bad!!!
7. I shoot Nikon, but a buddy of mine shoots Canon, and he and I did a star trail shoot this summer, and a single battery last each of us around 2 hours. For the best results, try to get at least an hours worth of exposures.

Have fun...it is a great way to spend an evening.

HFM

[LWimages]

Great tip!
Tagging this post for future reference.

Thanks

[lextalionis]

Wow, very nice Howard thanks for the help. I'll be shooting with a 17-55 2.8 with IS off and stopped down to f4 (that's enough?) Any way, I did read somewhere about taking the multiple shots but I'm a wee bit worried I won't be able to manage them in post-process. I've never stacked images before.

What's the benifit of using multiple shots vs. one single shot?

-Roy

[HFMarshburnJR]

Roy -

With my camera (Nikon D70), I start to get sensor fringing noise (caused by the sensor heating up) on any exposures longer than 5 minutes. This shows up as a purple area around the edge of the frame of my pictures. The black frame subtraction will remove most of that noise, but not all of it. The longer the exposure, the worse the fringing gets. And this problem occurs with all digital cameras. The only thing that varies is the amont of time before the problem manifests. So, to cut down on the noise, I have found this to be a useful method. Second, there is that nasty battery consumption problem - if youare taking multiple shorter images and your battery runs out of juice, you are only going to lose one small part of your final image, not an entire xx minute exposure. Third, when dealing with the night sky, or an area that might have unwanted spurrious light sources (like cars driving by) it is nice to know that you can delete a short frame or two from your final stack that include unwanted "stuff". Once again , the shorter exposure times allow you to do this without losing too much integrity.

As for managing the stack, I use Image Stacker. If you plan on doing these types of photos, this is the best $20 piece of software you will ever own. The total workflow to create the image you see in this reply was about 20 minutes - from raw captures to final stacked image. Here is the basic workflow:

1. With raw images imported to my computer, open all of the raw files in ACR. Make the necessary adjustments to the first image. Select all of the images and synchronize. Select all of the photos again and save all as JPG files to a new folder. Close ACR.
2. Open Image Stacker and select all of your JPG files to stack. Select the lighten mode for blending
3. It will take just a couple of minutes to create the stack. Take the saved JPG file and bring it into Photoshop to do any final tweaking you want to do.

This image is a stack of approximately 100-30 second images taken this summer. I was dealing with a full moon and light foreground elements , so the "shorter" exposure was required. I had never used Image Stacker before I tried it on this image - I will never go back to stack in Photoshop unless I am dealing wth a very small number of layers.

I hope this helps. Have fun!!!

HFM

[andyz]

Just on a related note, I think this is funny as to rules.
There are rules in photography.
Rules are meant to be broken.
"put your lens cap on and take one more 4 minute exposure" - Now that is breaking the rules!

On a more serious comment, Howard, I respect your work as it is excellent and I plan to save your tip list above. But as I look at your photo above, I think you must be quick from one shot to the next or you'll get breaks, and I see what looks like breaks on yours. The long, bright trail on the left of your shot has 3 breaks in it. Is this resolution of my screen setting, the low res image posted here or does that appear in the original stacked image? Would it avoided with a faster frame grab from one shot to the next, is it avoidable at all or a result of stacking?

[HFMarshburnJR]

Andy -

Good catch. That is not a problem with movement of stars. You have a few (more than 10)seconds before there is perceptible movement in the stars during trails. There was not more than one or two seconds between my exposures. What you are seeing is quick and sloppy PP. I removed some power lines that were in the foreground that were too prominent, and this version of the image did not get cleaned up after the fact. Also, if small gaps do appear because you fall asleep at the switch, just remember that the clone stamp tool can be your friend!

Good eye, and thanks for the kind words.

HFM

[andyz]

I love your work. Your road trips are fantastic.

Do you recommend painting with light on any of the foreground elements and was the stone building in your shot painted, or is that the natural accumulation of moonlight and ambient light?

[lextalionis]

Originally Posted by HFMarshburnJR

1. With raw images imported to my computer, open all of the raw files in ACR. Make the necessary adjustments to the first image. Select all of the images and synchronize. Select all of the photos again and save all as JPG files to a new folder. Close ACR.
2. Open Image Stacker and select all of your JPG files to stack. Select the lighten mode for blending
3. It will take just a couple of minutes to create the stack. Take the saved JPG file and bring it into Photoshop to do any final tweaking you want to do.

HFM

Wow, thanks for the great help! I don't see any mention about the "black" frame in your steps above. I insert the black frame with the same software?

Thanks,
Roy

[HFMarshburnJR]

Reply to Andy - Thanks for the very kind words. I am just learning, like everyone else. I have read up a lot on this topic and now had the chance to try a few things out to see what works best for me. These efforts have worked and fortune has smiled on me with the locations I have selected. In the shot above, the foreground lighting was done with the rising full moon. Would I recommend painting a foreground subject in the absence of other light sources? Like with most questions...it depends. If your vision for te image is to give attention to the foreground and the background of stars - Absolutely. If your vision for the image is to capture terestrial things in abstract against the vast beauty of the universe...leave the light alone. Thanks for the questions.

Roy -

Good catch - If you are doing relatively short exposures (like 30s to 1Min) - you probably don't need the dark frame subtraction. As you get up in the 4-5 minute and beyond range, you will need it. If you take a dark frame, wait until you bring the final stack back into PS before you add another layer and copy the dark frame in.

One other thing I forgot o mention - try to be precise with the timing on your exposures - It makes post processing a lot quicker and cleaner. I use a stop watch to time anything beyond 30s. And I use the camera to time anything under 30s. Have a great time at Enchanted Rock. It is a wonderous place.

HFM