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I have a Nikon D3300 and I want to do astro-photography. I have a 50mm prime lens and by the 500 Rule, I can click only up to 6.6 seconds without having star trails. Any idea how I can do it without buying any other lens?

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    \$\begingroup\$ You should provide a definition or a link to "500 Rule" \$\endgroup\$
    – Carl Witthoft
    Oct 19, 2016 at 11:24
  • \$\begingroup\$ @CarlWitthoft, divide 500 by your 35mm-equivalent focal length to get the maximum exposure time before star trails will show. \$\endgroup\$
    – Mark
    Oct 19, 2016 at 18:35
  • \$\begingroup\$ @Mark thanks -- doesn't that make some assumptions about the pixel density? You won't see a trail until the star's position has moved at least one pixel (or RGBG group if in color). So a 500-pixel-row sensor will resist trails ten times as long as a 5000-pixel-row sensor, all other things being equal. <--- including the physical sensing area. \$\endgroup\$
    – Carl Witthoft
    Oct 19, 2016 at 19:15
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    \$\begingroup\$ @CarlWitthoft The "500" or "600" rules have nothing to do with pixel size. They are based in the assumption of a display size of 8x10" viewed from 10" by a person with 20/20 vision. Neither rule of thumb would be remotely applicable for any amount of pixel peeping. \$\endgroup\$
    – Michael C
    Oct 19, 2016 at 19:32
  • \$\begingroup\$ @MichaelClark thanks for the additional info. All the same, if you don't have enough pixels to begin with, blowing it up to 8x10 is not goingto change the fact that the star position didn't move off the original pixel during the exposure time. \$\endgroup\$
    – Carl Witthoft
    Oct 19, 2016 at 22:33

3 Answers 3

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  1. Shoot as wide open as possible.

  2. Get into you car and drive as far away from light polluted areas as possible. This will make a huge difference in what you & your camera can see on the sky.

  3. Try shoot on a moonless night if you only want to shoot the stars.

  4. You should be able to build a simple motorized barn-door tracker , or this for a few bucks or even a manually driven one, and that will greatly extend you exposure times.

  5. Google tips on post-processing for nightsky photography. A lot of information can be recover from a night-sky shot in post-process

  6. use a shutter release or timer to prevent any shakes made by you.

  7. put a weight on your tripod to make it a bit more stable

  8. try to rent or borrow a lens if you can.

  9. There are amazing lenses for night-sky photography for great value like the rokinon 24mm f/1.4 or Tokina 11-16mm f/2.8 for example. I used the Tokina on a Canon APSC before and got mine for aroud 350 of ebay.

  10. Taking multiple exposures and stacking them together is another option you can use

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    \$\begingroup\$ "Taking multiple exposures and stacking them together is another option you can use" This is by far the simplest solution. \$\endgroup\$
    – ElendilTheTall
    Oct 19, 2016 at 14:28
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The obvious answer is to use a star tracker. Alternatively, you could just accept the star trails and make a virtue of them. One technique is to gradually defocus the camera during the exposure. This enhances the colours of brighter stars since the film/sensor is no longer saturated and bleached out. The astronomer David Malin is a well-known exponent of this technique.

Southern Cross, short defocused star trails (David Malin)

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  • \$\begingroup\$ Even on shorter exposures that won;t result in much, if any, trailing slightly defocusing also works to make brighter stars appear larger than dimmer stars and makes it easier to record the colors of different stars by spreading the light over more pixels so they don't get blown out on a single pixel or two. \$\endgroup\$
    – Michael C
    Oct 21, 2016 at 5:48
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If you don't have the option to buy a wide angle lens, there are a few things you can do:

  1. Make sure your aperture is open as wide as possible (f/1.8 in this case, I'd assume).
  2. Use a star tracker. You can build one yourself or buy one (NOTE: I haven't tried that particular one - I just did a search and linked to the first one.)
  3. Borrow or rent a wide angle lens. There are sites like borrowlenses.com and lensrentals.com where you can rent them for relatively little money. If you have any friends who are also into photography, maybe you could trade for a weekend?
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