Moon

Last night I woke up early to photograph the total lunar eclipse. It is my first time to shoot seriously, with tripod, cable release, and mirror lock-up. It was an interesting but difficult experience. At the end I got some decent shots and learned some lessons. Here are the things I have learned. 

  • Use a long lens. If you want to fill the frame on a APS-C sized sensor, you need a lens with focal length of ~2500mm. This is not very practical with affordable camera lens. You will need to get a telescope and the adaptor to connect your camera to the telescope. I used a Sigma 100-300mm f/4 with a 1.4X TC to get 420mm effective focal length. The size of the full moon on the sensor is only ~4mm, translating to about 650 pixels across in the final image. Not very good, but usable.
  • Prevent blur. There are two aspects of this. The first is the camera shake or vibration. To prevent this, setup the camera/lens on a solid tripod and use cable release and mirror lock-up. Delay the shutter release after mirror is locked up by a couple of seconds to allow the vibration caused by the mirror slap to fully dissipate. Avoid wind or accidental bump. The second is the motion blur cause by the moon’s movement. The empirical rule is to not let the exposure time to exceed “600/focal length” in seconds. For example, not exceed more than 1s exposure for a 600mm lens. You can open up the aperture and/or bump up the ISO on the camera.
  • Exposure. Get a proper exposure for shooting the moon is not always easy. The exposure are affected by the phase of the moon, atmospheric conditions, and the ISO settings of your camera. From full moon to thin crescent you may need to change the exposure across 4 stops or more. During the eclipse shooting, I used manual exposure and setup the exposure bracketing in such a way that I can clearly see blown highlights in the shot with the highest exposure. By using a 5-shot 1EV/step exposure bracketing this way, I had a safe bet to get a photo with a good exposure (may still need to adjust +/-0.5EV to taste in post-processing).
  • Focusing mode. AF should work pretty well. However I found it is difficult to align the focus point on the moon as the moon moves pretty fast across the sky, especially on a tripod. So I use auto focus to set the initial focus then turn to manual focus for the subsequent shots until I have to move the lens again before the moon move too far to the edge or out of the field of view.
  • Avoid lighted areas and use lens hood. This is to prevent stray lights getting into the camera.
  • Camera/lens settings: You may miss a few things when setting up camera/lens in darkness. Check the camera settings before shooting to make sure it is not in a wrong mode. If you use a zoom lens, make sure it is zoomed all the way out. I learned a lesson on this one. I didn’t realize I was shooting at 360mm, not 420mm until very late in the shooting so the moon was 100 pixel, or ~15%, smaller.

References:

  1. Moon Photography – A how to guide by Keith Cooley
  2. Photographing the moon by Dan Heller
  3. Some discussion threads on DPReview forums

P.S. : The full moon shot was taken the next day since I missed it first time. 😉

Posted in: Tips and Techniques on August 29th, 2007. Trackback URI

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