Shooting the night sky

[scorpion_tyr]

Are you sure it's focused to infinity? Many times this is the problem since a lot of lenses will have the infinity mark, but the infinity focus is just before that mark. If there are any visible lights in the far off distance, select auto focus, focus on one of those, select manual focus, now look where the mark is. If you're using a wide angle lens, this will be where the infinity focus is.

Also try shooting a full stop or two above the max aperture, most lenses are visibly less sharp at their max and min apertures. Shooting at night is not easy at all. It takes a long time to learn, and a lot of experimenting.

 

[Synax]

What do you mean by full stop above aprrature ?

 

[pgriz]

What do you mean by full stop above aprrature ?

If your minimum aperture is (say) f/3.5, then either f/5.6 (1-1/3 stop) or f/6.5 (2 stops) would give you more sharpness. However, closing down the lens to get more sharpness also means that you're going to need a longer exposure. That's where experience tells you what is more important in each case.

 

[Synax]

Ah okay. I have a shutter control with me. It arrived today and it's pretty cool. I'll try what you told me but I've been messing around with the settings and I just can't get any cool pictures with the lens and camera i have. Makes me sad haha. I want to achieve close to some of these f2.8 pictures but it isn't working. Maybe it's just the light pollution but I'm still trying!

The highest ISO I can get is 1600 and aperture of f3.5 like I said. Sadly I can't see the Milky Way for a couple months

 

[pgriz]

ISO 1600 is fine. f/3.5 is fine. Focusing is REALLY important (but I think you've figured that out already). Minimizing all sources of camera movement/vibration is also important (so solid tripod, remote shutter release, plus functions such as mirror-lockup are all contributors to minimizing this).

I'll show you what I can do with my camera (T1i + 24-105mm f/4 lens). Each shot was at ISO 800, f/4, 30 seconds with long-exposure noise reduction (actually, a dark frame) on. IS, AF were off. Focus was achieved manually, using live-view on Polaris. Focal length was 24mm. Images were saved as RAW files, processed by Canon DPP software. Frames were then either stacked using the freeware Deep Sky Stacker (DeepSkyStacker - Free) or merged into sky trails using Startrails freeware (Startrails application). The star simulation screenshot is from Stellarium (another freeware program: Stellarium). All images below were resampled and resized to 1050 pixels x 700 pixels, and resharpened after resizing.

So, the first image is a single frame, with the dark field applied by Canon DPP, and some adjustments to the curves and light point max.:

This image is of 30 such frames, stacked with Deep Sky Stacker, saved to TIFF, and further processed with Canon DPP:

This image is a screenshot from Stellarium, showing the field above.

This image is a stack using the freeware Star trails application:

You'll notice that all the startrails above have little gaps on the star trails - that comes from the time the earth moved while the camera was doing its 30-second dark frame.

The above were all taken while I was helping my daughter do a star-trail assignment for one of her classes, and the idea was to show the apparent movement around the celestial pole. Note that Polaris, the bright star closest to the center of the rotation is not exactly AT the pole.

 

[Synax]

Thanks for the post. So a couple questions... If I can only get sharp images with those aprratures I need a long exposure correct. What I'm getting it is... Will it be the almost the same outcome as if it was a 2.8 at 30 seconds and if it was at 5.6 at 60 seconds? You know what i mean?

 

[pgriz]

Exposure-wise, yes, but at 60 seconds, you'll have twice as much star motion as at 30 seconds. Unless you invest in a tracking mount (see Tim Cambell's posts) to allow the camera to exactly compensate for the earth's rotation, which will then allow you to run much longer exposures without having the stars trail.

As for getting the ultimate sharpness - the aperture is important, but getting the focus right is even more important. Once you know you can reliably nail the focus, then adjusting the aperture would be the second step.

Don't forget that all this assumes you have a rock-steady mount and the camera is not doing any moving of its own (unless it is solidly bolted onto a very solid tracking mount).

 

[Synax]

Ah okay. Well star trails are pretty cool especially with objects in your photo. I think I'm getting the hang of the settings but I need to learn the focusing. Don't think I've been doing that. Any tips on proper focusing? Also... If lets say you wanted a person to be in the photo while you're capturing star trails with long exposures... Does the person have to be there still for the entire time? Or...?

 

[pgriz]

Ah okay. Well star trails are pretty cool especially with objects in your photo. I think I'm getting the hang of the settings but I need to learn the focusing. Don't think I've been doing that. Any tips on proper focusing? Also... If lets say you wanted a person to be in the photo while you're capturing star trails with long exposures... Does the person have to be there still for the entire time? Or...?

If you have a person in the foreground, then you need to think about your depth-of-field, which is linked to your aperture+focal length. Here the concept of hyper-focal focusing comes into play. See this link to figure out how to get the "right" aperture for what you're trying to do: Online Depth of Field Calculator. What you will find is that you need a smaller aperture to get the required depth-of-field, which then makes your exposure required longer.

As for having the person stay in the picture the whole time you're exposing, that generally is not required (unless you're going for a silhouette). Usually, there is a flash that serves to illuminate the stuff in the foreground, after which the person can move away, and the exposure continues. However, now you have to figure out the amount of flash power you need to give you the effect you want, and again doing it manually will give you much more control over the appearance of the image. For this purposes, OCF (off-camera flash) is the preferred way to go, but this means you need some way of synchronizing your flash with your exposure, something that is usually accomplished by using radio triggers.

 

[pgriz]

Another way to do this is to composite your image, with one set of exposures for the night sky and another for the foreground-midground. One rather clever way I've seen done is to shoot the foreground/midground during dusk, when there's enough light to show the ground detail, and then, without moving the camera, shoot the night sky using the appropriate settings and merging the two images together in Photoshop or similar editing program.

 

[Synax]

Oh okay. I'll experiment tonight. Also some of the pictures I've seen of night sky shots have pretty colorful skies... Is that edited or is that raw? My guess is people change the temp using software?

 

[jsecordphoto]

It sounds like you're trying to run before you can walk. I've done star trail photos with people in them, using layer masking.

Introduction to Landscape Astrophotography

Read through that. My buddy Adam wrote that tutorial, I learned a lot from it when I was starting out and Adam is one of the best astrophotographers I know.

 

[Synax]

I'll check these out thank you. Yeah I think I'm expecting too much from one image. I just learned more about white balance and realized that stacking a bunch of images and editing a few things with software will create these nice looking images. I thought these beautiful images that people take come straight from the camera. well maybe they do... I have no idea haha.

 

[wfooshee]

Again with focusing, use the Live View and focus on something at a good distance. As far as lenses this size is concerned, 5 miles is infinity. If there's nothing you can see when you're out there to focus on, set it before you go and don't touch it again.

Focusing on a star in Live View is possible, but something brighter is easier. Zoom the live view as high as you can for the best look.

Putting the lens against the stop at infinity is probably actually past infinity. For tolerances, the actual infinity focus is just before the lens runs out of travel.

 

[Synax]

Yesterday night i found the brightest thing in the sky which I believe was Jupiter and I zoomed into it with live view. I adjusted the focus and zoomed again adjusting the focus once again. Then I zoomed back and that was how I got my focus. It was barely below the infinity. My image looked a lot better than previous ones I took.

I adjusted the focus so the light was smaller than it was before. I think that's what you're supposed to do right?