AstroPhotography - Milkyway?

Discussion in 'Beyond the Basics' started by Boombeat, Sep 16, 2012.

  1. Boombeat
    Offline

    Boombeat New Member

    Joined:
    Sep 5, 2011
    Messages:
    15
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    Malta
    Gallery:
    Ratings:
    +0 / 0
    Yesterday i tried shooting some pics of the milky way but the best i got was this.

    Milkyway | Flickr - Photo Sharing!

    I used a canon 550d with stock lens 18-55mm. This pic was taken at around 20 seconds exposure time , f3.5 with an iso of 1600 .
    Is there a way to get more details?

    Thanks
  2. KmH
    Offline

    KmH Helping photographers learn to fish

    Joined:
    Apr 9, 2009
    Messages:
    34,050
    Likes Received:
    4,066
    Trophy Points:
    113
    Location:
    Iowa
    Gallery:
    Ratings:
    +4,073 / 1
  3. ryanwaff
    Offline

    ryanwaff Active Member

    Joined:
    Dec 25, 2011
    Messages:
    181
    Likes Received:
    50
    Trophy Points:
    28
    Location:
    South Africa
    Gallery:
    Ratings:
    +50 / 0
  4. pgriz
    Offline

    pgriz Well-Known Member

    Joined:
    Jul 30, 2010
    Messages:
    4,872
    Likes Received:
    2,231
    Trophy Points:
    113
    Location:
    Canada
    Gallery:
    Ratings:
    +2,255 / 1
    Between you and the stars, is a lot of air. Good thing for us, otherwise we wouldn't be here to admire the stars. But the air has stuff in it (clouds, dust, various aerosols), and varying density, which tends to distort the light we do see, and reflect light from the ground and the moon, causing the apparent sky background to be much brighter than it would be if we were in space. So the first lesson in taking sky pictures at night, is to find a location which is as free from light pollution, and as high above the bulk of the atmosphere, as possible - that's why all the major telescopes are found in remote areas on top of high mountains, in locations where the air flow is "smooth". Now, if your ancestors did not have the presence of mind to choose to live in such an area, you'll just have to find the darkest spot within reasonable distance from where you live.

    Next, it helps to NOT have the moon shining brightly - all that light bounces off the dust in the air and reduces the sky contrast. So shooting when the moon is close to new would be good.

    Next, you deal with the earth's rotation, that makes the stars move in the sky. Earth moves at 15 arc-seconds each minute. If you are using a stationary tripod, depending on the focal length you use and the crop factor, this means that you can record about 1 minute with a 24mm lens on a crop camera, and less than 10 seconds with a 200mm before the stars start to trail. If you have a way of countering the rotation of the earth, say with an equatorial drive, then you can expose for many minutes without worrying about stars trailing.

    Assuming you don't have access to an equatorial drive, the way to get good images is to have relatively short exposures, which are then stacked, as Keith (KmH) noted above. The stacking is a well-known technique which allows the random noise to be reduced, and the signal to be amplified.

    Try using ISO 800, the widest aperture you have on your lens, the shortest focal length, and a shutter speed of about 20 seconds. Take a shot, then check the image, blowing it up to see if any images are trailing. If so, reduce your shutter speed. Once you have a good shutter speed, take a series of 10-30 frames, import them into the computer, and do some preliminary processing on them. If your software has the sliders for dark point, light point, and mid-point, move the midpoint over towards the dark point, which effectively boosts the background to lighter values. Stop before the noise becomes very visible. Once you have this setting, repeat the exact same setting for the rest of the frames. Now import them into the stacking software and register them. Depending on the software, you may have a variety of options to help you carry out this registration/stacking exercise. At the end, you should have a much better result than if you had only the individual frames.
  5. Edsport
    Offline

    Edsport Active Member

    Joined:
    Nov 30, 2010
    Messages:
    862
    Likes Received:
    73
    Trophy Points:
    28
    Gallery:
    Ratings:
    +73 / 0
  6. Ulriksen
    Offline

    Ulriksen New Member

    Joined:
    Nov 3, 2011
    Messages:
    82
    Likes Received:
    10
    Trophy Points:
    0
    Location:
    Norman, OK
    Gallery:
    Ratings:
    +10 / 0
    Great sharing edsport, I basically loved that article/post!

Share This Page