Total Lunar Eclipse - Time-lapse Planning

Tomorrow (January 31, 2018) morning there is a total lunar eclipse visible from much of the US and Asia, as well as Australia.  Around here in Minnesota (and even more so further East), the moon will set during totality.  This eclipse can be considered special since it's a total eclipse, blue moon (2nd full moon in a month), and "super" moon (closer than typical) all at once.  I hope to capture a time-lapse of it, however at this point the forecast looks like it will be cloudy, so if that doesn't improve to at least give a little hope, I might not bother going out that early.

For those hoping to capture a time-lapse of the lunar eclipse as well, here are some things to keep in mind when planning.  I don't know if it will work out for me with the weather or not, but I would love to see what you get!  Send me a message or share on the facebook group.

Interval Settings

The full eclipse from the first partial to the end of the partial after totality will be about 3.5 hours.  If you want the final time-lapse to last 20 seconds at 30 frames/second, you'll want to end up with 600 frames (20*30).  To determine the interval, we'll divide the total seconds by 600, which would be (3.5*60*60)/600 which gives us an interval of 21 seconds.  In my location, the moon sets half way through the eclipse, so if I want to end up with 600 frames, I'll half that interval and go with 10 seconds so I get there twice as fast.

Keeping the moon in the frame

The earth turns at 15°/hour (360/24), and the moon orbits the earth about every 27 days, so it's moving at about 0.5°/hour (360/27/24) relative to the stars toward the East.  This means the moon moves at roughly 14.5°/hour across the sky.  This is what we'll need to know in order to make sure we keep the moon in the frame for the duration of the eclipse.

Fitting it all in a static shot

It's about 3.5 hours from the start of the partial eclipse to the end of the partial eclipse, so if you're in a location where the whole range is visible, the moon will move about 3.5 * 14.5° = ~51° during the eclipse. If you want to capture this without moving the camera, you'll need a lens wide enough to cover 51°.  On a full-frame camera, a 35mm lens will cover 55° horizontally and 37° vertically, and a 24mm lens will cover 53° vertically.  If the weather works out here, I plan to setup one camera with a 35mm lens to capture it (I'll only see half of totality before it sets, so this will be about right), and another with motion tracking with a telephoto (300mm on a 1.6x crop sensor).

Equatorial tracking

If you have an equatorial mount, you can align it with polaris and track the moon this way as the mount turns at 15°/hour with the stars.  The moon will still move at about 0.5°/hour slower than the stars, however, so keep this in mind if you have a very narrow field of view with a telephoto lens.  

Motion tracking with the VIEW

The VIEW with the latest beta firmware (v1.8-beta15) can track the moon when used with a pair of Genie Minis or the Dynamic Perception NMX controller with the Sapphire or pair of Stage-R heads.  Info on connecting these systems can be found here: http://docs.view.tl/#motion-control

If you have a VIEW with a GPS, make sure it's enabled and showing that it's got coordinates in Information->GPS Info and that the little location icon is in the top bar.

If you don't have a GPS, manually enter the coordinates, time, and date, in Settings (Set UTC Time, Set UTC Date, Set Latitude, Set Longitude).  Find the current time in UTC here: http://time.is/UTC

Once you have the location data setup and the motion system connected, select "Moon" under Motion Tracking when setting up the time-lapse.

Exposure

When setting up exposure, I would recommend exposing for the highlights of the moon at the start, and then setting the VIEW to Auto Ramping mode.  The moon moves quickly, so for sharp images, make sure to keep the shutter speed fairly fast.  This will mean keeping the lens wide-open, although the full moon before the eclipse will be very bright.  You may want to limit the shutter speed on the VIEW so it doesn't ramp it up to be too long, but remember this will also force the ISO higher as needed for exposure.


 

Elijah Parker1 Comment