Night Sky - Star Trails

Discussion in 'Beyond the Basics' started by benjyman345, Sep 8, 2007.

  1. benjyman345

    benjyman345 TPF Noob!

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    hi,

    I just setup my tripod and camera with iso 100 film and set to f8.0 on bulb.

    How long (approx) should i keep the shutter open to get an acceptable exposure. I am in a suburb, but well away from lights.

    thanks
     
  2. neea

    neea TPF Noob!

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    I live very far away from any major city.. basically the middle of no where :)

    I've had a small amound of trail at 30 seconds (venus.. oh she's so pretty!!) and quite a bit more at around 9-10 MINUTES.
    I'd love to post them for you to show examples but I dont have them on my work computer.

    I just recently baught a remote shutter for this exact purpose.
    10 minutes is the longest I've done so far.
     
  3. Buszaj

    Buszaj TPF Noob!

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    I've had the same question as you and got replies that try 30 minutes exposure, but since you are in a suburb, try raising the aperture to 12 or something like that.
     
  4. astrostu

    astrostu Guest

  5. wildmaven

    wildmaven TPF Noob!

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    Astrostu, you're my new best friend! :) Great tips!

    Benjyman, have you ever shot night sky pictures from your location before? I'm 20 miles away from a moderate city, and am up in a forest, but I still pick up the lights from the city.
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    Depends on the suburb too. We moved just 5km towards the city. In the old place I got a 6 hour exposure easy. Here I'm lucky if I can get 20 minutes with the same star brightness.
     
  7. nagoshua

    nagoshua TPF Noob!

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    Im just wondering... how do you go about focusing on stars... even on a fast lens i cant see them well enough to focus.
     
  8. astrostu

    astrostu Guest

    Another excerpt from my guide:

    Let's face it: It'd be nice if the "infinity" focus location on the camera lens really did focus at infinity. But - in my experience - more often than not the infinity focus position is "past" infinity, and you need to back-track slightly in order to get the camera lens properly in focus. But how can you tell on that tiny little view-finder if your star is in or out of focus?

    One way that I've used is to focus on the Moon. It's big enough that you can usually tell when you're in or out of focus without taking a picture.

    The second method I use - for when the Moon's not out - is to take a picture of the brightest object in the sky (Venus, Jupiter, Sirius, or another bright object), and then zoom in all the way on the LCD screen on the photo. If it looks like the bright object is too big, I adjust the focus slightly and try again. I continue this until I've gotten it as good as I think is reasonable.

    The third method - and I only do this if focus is extremely important and I'm imaging for a long time on deep-sky objects - is to do the above method, but have the image pop up live on the computer screen (requires proper software and cables). I can then zoom in in the camera's software or PhotoShop and actually measure how many pixels across the object is. I can then adjust the focus slightly and repeat the process and see if it got better.

    If you use method 2 or 3, I would suggest starting at the farthest "infinity" setting your camera lens has. Then work your way downwards from there.
    Also keep in mind that on many zoom lenses (in my experience) the exact "infinity" focus location will change slightly depending upon what focal length you have your lens.
     
  9. JamesD

    JamesD Between darkrooms

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    Benjyman,

    Since you're using a film camera, you obviously can't use the LCD screen to check your exposure or focus.

    Based on what I recall of photographing the aurora borealis, a good starting point for F/8 and ISO 100 might be around 8 to 15 minutes. However, keep in mind that is this exposure timeframe, you're quite likely to run into reciprocity failure, which means you'll have to further increase exposure, either by using a longer duration or wider aperture.

    As for focus issues... it can be tricky with a film camera because there's no LCD display to zoom in on. (Unless, of course, your vision is sharp enough to make out dim, small images in the viewfinder, which mine certainly isn't.)

    What I usually do is focus on the horizon, then turn off the autofocus (so the camera doesn't try to search for focus when I trip the shutter). At f/8, any normal or wide angle lens will have the sky in sharp focus if focused on the horizon. In fact, with a reasonably wide-angle lens, everything beyond a few feet should be reasonably sharp, or in "acceptable" focus, at f/8, if you're focused anywhere near infinity.

    I'd suggest bracketing both aperture and exposure duration a couple of stops each way on the first night you shoot, and keep exposure notes. Get the roll developed (make sure you tell the lab they're night-sky photos, or they may not print them at some of the cheaper places) and examine the prints. Find the ones that seemed to come out best, check your notes, and use those exposure settings as your starting point for future sessions.

    Hope that helps, and good luck!
     
  10. fightheheathens

    fightheheathens TPF Noob!

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    1. its best to shoot on a night with out a moon. the moon is very bright and blocks out alot of stars

    2. being in an urban area will cause light polution to show up in your shots
    if you can even traveling 30min outside of the city will help.

    as far as exposure?
    as long as you can. follow the link to see a star trail shot.
    film was 50 iso, f/8 exposure was 5 hours i think...
    http://img.photobucket.com/albums/v47/wewillfighttheheathens/7-1.jpg
     

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