I have always had an interest in astrophotography. It’s amazing to see some great images from other photographers where they have captured stars, planets and nebulas, just to name a few. Awhile back I tried this a couple of times before, but with limited success. Photographing the moon was quite easy compared to this, as that is actually a daylight photo set up. You can see that post here.
My mission for this project was to try and catch some of the clusters of stars and clouds of gas that I had seen before. When I photographed the sky before, my images were blurry, or star trailed rather. I did some research and found out a few things. First, you have to do a little math. The common thinking is that you have to use the number 600 as a base. How this works is that you divide your focal length into 600 and that gives you your shutter speed. I bet you are thinking, “What did he just say? Let’s use a real example. On my Nikon I wanted to use my widest prime lens as that is one of the sharpest lenses that I have in the bag. This happens to be a 24mm. Here is what this looks like: 600/24mm=25sec. We take 600 divide it by 24mm (the focal length of the lens) and it give us 25 seconds for our shutter exposure. What does all this math have to do with the photo? I wanted a photo without any star trails. Doing this math ensures that with whatever lens that you have on your camera, that you will get a photo without star trails. The good news is that, this is the hard part. The rest is cake.
You might be asking, “What about the ISO and aperture?” That’s a good question. I opened up the lens as far as it would go, in this case f/2.8. You would think that at 2.8 that everything would be soft. Well, not exactly. When you are photographing something that is hundreds of thousands of miles away, everything becomes sharp because of the distance of the subject to the camera. Also, this will let in the maximum amount of light that is traveling from the stars. So in a nutshell, use the widest f stop that your lens has. For the other half of the puzzle, it’s good to start at ISO 800. This is where a camera that does well with high ISO shines. When you take your test shot, see if you are getting mostly black. If you are, then you are at the right exposure. If you have some of the city lights reaching into your exposure, then try a lower ISO.
This works best if you live out in the middle of nowhere. Any ambient city lights will taint your photo. I read that the beach works well shooting over the water. This is great, but what if you live in Kansas? Your hosed….JUST KIDDING! If you live in the middle of a land mass, just find a place that is out of the city. Also, you want to do this when there isn’t any phase of the moon out. You want a BLACK, CLEAR sky with twinkling stars.
It’s time for some equipment choices. The most important piece of equipment should be a tripod, or something that can hold your camera absolutely still. I have a Manfrotto tripod with a ball head. It was the best piece of equipment that I invested in (next to the camera…duh!). If you don’t have a tripod, you can place the camera on the roof of your car and prop it up with something. The next best piece of equipment for this is an electronic release. This allows you to take a photo without touching the camera. If you don’t have one of these either, use the camera’s self timer.
Here was the other piece of the puzzle that I was missing when I did this the first time. Apparently most photographers take multiple photos of the same scene and “stack” them together. The exposure isn’t changing like in HDR. This is supposed to help with the noise issue, as I understand it. We’ll get the stacking part in a minute.
Here we go we are now ready to take some starry photos. The camera is on a tripod or solid surface, and we have the release or self-timer ready to go. Whoops, one last thing, the focus. Cameras sometimes have a hard time focusing in the dark, so we are going to help it out. Choose manual focus on your camera. Move the lens focusing ring to the infinity sign. It looks like a sideways 8. Most lenses aren’t at their sharpest at this setting, however if you move the focus ring back just a hair, it will be perfect. I’m not a lens expert, but I have learned this trick from many pros before me.
By the way, if you haven’t figured it out, we will be using manual for this. Don’t worry it will be ok. The world won’t blow up in your face because you are leaving “auto” or “aperture priority” for a bit. Choose the ISO as discussed above. Choose the lens’ lowest f stop, and when you did the math, it gave you the shutter speed. All right, press the shutter and see how your exposure looks. If it’s a muddy black or has color in it, chances are that you have some ambient light creeping in. To fix this, lower your ISO. If you are having the reverse problem and the stars are not as visible, crank up your ISO. Take at least five images one after another and don’t move or bump the camera.
Congratulations! You are now a NASA photographer! Don’t we wish it was that easy. You are half way there. All of the images are on your camera card. Now we need to put them together to make our final image. There are two ways to do this. You can use an official “stacking” program that is marketed to starry folks or if you have Photoshop Extended you are all set. The key word in that last sentence is EXTENDED. There are two version of Photoshop, standard and extended. If you want to look at some of the stacking programs for astrophotography you might like Deep Sky Stacker. This is a PC only product. If you are Mac based like me, I used Photoshop CS5 Extended. But, don’t have Photoshop Extended, do a Google search for “Deep Sky Stacker Mac” and a bunch of other companies come up.
For this discussion, I’m going to stick with Photoshop as that is what I have and used. Once you have all of your photos copied to your computer, launch Photoshop. Then you are going to choose: File -> Scripts -> Load Files Into Stack. When the following window appears, browse for your files and check the boxes that say “Attempt to Automatically Align Source Images”, and “Create Smart Object After Loading Layers”. Depending on how many images you have selected, this would be a good time to get your favorite frosted beverage and let the hamsters do the rowing.
Once Photoshop has done its thing; all you need to do now is choose Layer -> Smart Object -> Stack Mode -> Mean. This will create what you need. Lastly, I would put an S with the curves adjustment layer and possibly bump the vibrance.
After all was said and done, this is what I ended up with. Be sure to click on the photo to see the bigger size.
I hope that you give this a try some day. It’s amazing what we haven’t been able to photograph as of yet in the sky, I’m sure that as technology gets better, we will be able to see deeper into space. I found that this could be a pit it you aren’t careful. Serious folks buy powerful telescopes and get special camera mounts for their cameras. Some I have seen range from the $500 price point to over $10,000! I would rather have a new Nikon D4 when it comes out. (I’m taking donations if anyone is inclined….kidding…well, not really if want to write a check!)
Until next time…
Keep Your Glass Clean