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I've tried but I don't think my kit is good enough. How do you take pictures of something like the milky way?
And if you've never actually SEEN the milky way, then you definitely MUST take a trip to go and see it (preferably around the Rockies if you're in the States) because it is unlike any other sight you have ever seen. I was almost moved to tears seeing it.
I've seen some folks take pretty good pictures, but I want to take some of my own, of course.
Would film be better? Worse?
Catching the Light has a lot of information on astrophotography and is a great place to start.
However, with just a dSLR, it can be pretty challenging to do deep space photography, many are using telescope with mount adapters for their cameras and motorized star tracking to keep everything in focus. The last is a big factor, without star tracking, of some sort, you're going to end up with star trails which, admittedly, can look really cool.
As for film versus digital, it probably doesn't really matter. One thing, however, to bear in mind with some digital cameras is something called "dark frame subtraction" (or long exposure noise reduction) which is used to remove sensor noise, usually from heat. Many cameras allow you to turn this off, which you want to do, but some don't, so check your camera model to be sure. In general, it is better not to have that on because it will double the length of time for each exposure and it can usually be handled in post processing with a single dark frame you take yourself. A dark frame is just a long exposure with the lens cap on.
Anyways, the website I linked has a lot more detail and probably explains it better than I am...
There are several threads here on Photo.SE that discuss astrophotography. They might also be of help to you, and you can find the top two here:
You might also like the Astrophotography tag.
Regarding equipment, there are some basic rules that can help you out. The first one has to do with focal length. The longer the focal length, the quicker you tend to get star trails. A 180mm lens will get star trails pretty quick, less than 20-25 seconds usually, since it is imaging a smaller area of the sky. A wider lens such as a 50mm will get star trails slower, around 30 seconds or so. A very wide lens, like 24mm or wider, will allow you to take exposures up to 45 seconds or so without visible star trailing.
Effective focal length is dependent on sensor size. If you have a full-frame sensor, a 50mm lens or wider is great to get milky way shots with decently long exposures without star trailing. On a APS-C sensor, like most entry-level and mid-level (and some high end) DSLR's, a 35mm or wider lens would be ideal for full-sky milky way imaging.
The maximum aperture of a lens can be critical to getting a good shot without star trails. I myself am somewhat limited with an f/2.8 16-35mm lens. I would recommend at around one stop faster than f/2.8, which would be f/2 or f/1.8, to get a decent night sky/milky way shot. Obviously, wider lenses give you more capability. The next lens on my list is either the Canon EF 50mm f/1.4 ($350), or the Canon EF 50mm f/1.2 ($1450). If you want to experiment on the cheap, the Canon EF 50mm f/1.8 is one of the cheapest lenses you can buy at $99.
ISO speed is a key factor in milky way astrphotography. Most milky way shots are "short-exposure" astrophotography, where the shutter is open between 20 seconds and perhaps a minute. Any longer, and the motion of the sky will start to "drag" the stars across the sensor, creating trails (startrails.) With short-exposure astrophotography, you want to absorb as much light as you can without massively blowing out the point lights of the stars themselves. Higher ISO settings, such as ISO 800 through ISO 3200, are best for short-exposure milky way shots. Higher ISO helps you keep your exposure times below the visible startrailing limit, and helps gather more light in the darkest parts of the frame. Images can be corrected during post-processing to reduce exposure back to realistic levels and mitigate noise.
If you wish to get the best sky photos, a tracking mount is a must. Tracking mounts are fairly pricey, ranging from $900 up to several thousand. There are two types, alt-azimuth and equatorial. Alt-az mounts are ok for "shorter long-exposure astrophotography", but they introduce an increasing tracking error the longer you track with them. To maintain ideal tracking, an equatorial tracking mount would be necessary. With a tracking mount, you can expose for considerably longer periods of time at lower ISO settings, gathering more detail and gaining better saturation than is possible with short-exposure astrophotography. You also have the option of exposing multiple exposures of the same part of the sky for several minutes at a time, with dark frames in between normal frames. (Dark frames are exposed for the same time as the previous frame, but with the shutter closed to gather information about fixed position and fixed pattern noise that can be eliminated during post processing.) Specialized astrophotography "stacking" tools can be used during post-processing to merge your series of exposures together and get a nicely saturated, low-noise image of the night sky. Long-exposure astrophotography also greatly expands the range of lenses you can use, anything from very wide angles, to telephoto angles, and even to mounting your camera body on a telescope for true deep-sky astrophotography.
An interesting alternative (not that good but cheaper) of the tracking mount mentioned in the previous answers is a DSLR which can shift the sensor based on GPS information.
According to the Pentax OGPS-1 news release:
When mounted on the PENTAX K-5 or K-r camera body, the O-GPS1 also offers the advanced ASTROTRACER function,** which couples the unit with the camera’s SR (Shake Reduction) system for the effortless tracing and photographing of celestial bodies. The unit calculates the movement of stars, planets, and other bodies using the latitude obtained from GPS data and the camera’s alignment data (horizontal and vertical inclinations and aspect) obtained from its magnetic and acceleration sensors, then shifts the camera’s image sensor in synchronization with the movement of the objects.*** As the result, stars and other bodies are captured as solid points rather than blurry streaks, even during extended exposures. It also makes astronomical photography much simpler, as it requires only a tripod and eliminates the need for an additional accessory such as an equatorial telescope.
** This function is available only when the O-GPS1 is mounted on a PENTAX digital SLR camera body equipped with a magnet-driven SR system. *** The duration of ASTROTRACER operation may vary depending on photographic conditions.
Whether you use film or digital, you will want a fast lens and probably high ISO film or a high ISO setting on your camera. Larger sensors or film size are better. If you don't want streaks you may need motorized equipment that turns with the sky (for long exposures).
:D
Oct 28, 2010 at 23:21
:D