I've planned my supermoon eclipse shot: what could possibly go wrong?


You’ve done your homework, scouted your location, checked the timing of the various eclipse phases, and understood the position and movement of the sun during the event. Your camera bag is packed, sensor cleaned, batteries charged. What could possibly go wrong?

In this post, I’d like to cover just some of the key aspects of planning that you might want to double check to avoid disappointment during the “supermoon” total eclipse on Sunday/Monday. After all, the next “super eclipse” is not until 2033, so it’s going to be critical to get things right on the night!

In planning your shot, you may have made use of The Photographer’s Ephemeris to check the moonrise times and directions. While the information the app produces is very accurate, it’s important to make sure you’re asking the right questions. Here are a few potential gotchas.

The moon didn’t rise where you said it would! (Part 1)

One of the most common mistakes is to take the time and direction of moonrise (or sunrise, sunset, moonset etc.) and plan around that when you don’t have an unobstructed view of the horizon. If there’s a building, a hill, a ridge or forest in the way, then you can’t see the horizon and the moon won’t appear at the given moonrise time.

If there’s a building, a hill, a ridge or forest in the way, then you can’t see the horizon and the moon won’t appear at the given moonrise time.

Rise and set times and directions are always calculated relative to an unobstructed horizon. When you hear the TV weather person say the sun will rise at 6:42am in London, they’re meaning that’s when the top of the sun will peek over the ideal horizon. You don’t hear different sunrise times for people living west of Primrose Hill vs. those in Wapping. That’s because the sunrise time assumes an unobstructed horizon.

Therefore, if your shot depends on the moon appearing from behind Mt. Baker on cue, you can’t simply use moonrise time with the red pin dropped on the mountain.

So what should you do? Use TPE’s Geodetics function to determine the angle from your shooting location to the top of the obstruction, and then find when the moon is at the same or higher altitude. Here are some tutorials on how to do it:

The moon didn’t rise where you said it would! (Part 2)

So, you have an unobstructed view of the horizon. You’re in position at the appointed time, and looking in the right direction, determined using a high quality field compass.

The moon appears at the right time, but off by several degrees to the right or left. Why?

Chances are there’s a mix up between magnetic north and true north. In TPE for Desktop and TPE for Android, all azimuths and bearings are relative to true north. Your field compass will indicate bearings relative to local magnetic north, which can be several degrees different, depending on your location.

Magnetic declination difference

TPE for iOS allows you to choose between true north and magnetic north in settings: make sure you have the right setting selected based on how you’re planning on sighting your shot in the field!

Knowing the local magnetic declination (difference between magnetic and true north) is essential when using a field compass, and allows you to convert freely between azimuths relative to either pole.

The moon didn’t rise where you said it would! (Part 3)

You’ve checked the horizon, geodetics and ensured that you have the right azimuth. Moonrise comes and goes, but you still can’t see it. Why?

At full moon, the moon is rising near the time of sunset, and typically the skies are still bright. Combined with haze, pollution or cloud on the horizon, this can often make it difficult to see the moon at the moment of moonrise. (And remember, moonrise is the moment when the top of the moon is at the visible horizon – i.e. most of it is below the horizon.)

So, it’s perfectly normal not the see the moon for a few minutes after moonrise as it clears the layer of haze and the skies darken.

If you’re lucky enough to be in one of the locations where the moon rises or sets during the total eclipse, it may be doubly hard to see as it approaches the horizon. A totally eclipsed moon is much much darker than normal. You’ll see big differences in exposure settings between partial and total eclipse phases. There’s even a special scale to measure the darkness of a totally eclipsed moon: the Danjon number.

There’s even a special scale to measure the darkness of a totally eclipsed moon: the Danjon number.

To be sure of capturing the totally eclipsed moon as it rises or sets, try to plan to shoot it during the early part of dawn or the later part of dusk (i.e. civil twilight), when the sun is below -4° Above that attitude, and the combination of brightness in the sky and atmospheric conditions might make it tough to see.

There are too many people! I can’t get to my spot

I suspect that the Sep 2015 Blood Supermoon will likely be the most watched moon event ever. The level of press coverage is off the chart. Additionally, there are more well-informed photographers than at any point in human history.

Chances are you won’t be alone at your planned location, so be sure to get there early. And if things get over-crowded, just try to soak up the spectacle and avoid any photography stress!

Why isn’t the moon eclipsed? It should be!

Time zone. This is the most likely reason why the moon isn’t appearing as you expect it. NASA gives the times of the eclipse in UT (Universal Time). So, if you’re translating to your local time zone, be sure to allow for correct difference from UT and also for any daylight saving time adjustment.

Of course, there are easier ways:

  • The moment of greatest eclipse occurs 3 minutes before full moon, so, if you know the moment of full moon, you’re pretty much on the money for the eclipse too. Given that the eclipse lasts 1 hour and 12 minutes, you should plan on being ready at least 45 minutes before full moon to capture all of totality
  • This link will open the TPE web app right at the moment of greatest eclipse: http://ephemer.is/1OzXsDx. You can change the location to find the local time in your area (the moment of greatest eclipse doesn’t vary with your location on Earth).

The detail in the moon is blown out in my shot

The first factor that might cause this is variation in lunar brightness. As mentioned already, the brightness levels of the moon vary wildly during a total eclipse event. You’re going to need to adjust your exposure as you go to compensate for the amount of sunlight reaching the moon.

Secondly, it’s not always going to be possible to expose for both the moon and a foreground in your shot. If you’re shooting the partially eclipsed moon rising over a city skyline, you’ll probably be fine for the first 10 minutes or so after sunset. However, once the skies darken (e.g. when the sun is more than 3° or 4° below the horizon, the partially eclipsed moon will be very bright relative to the cityscape. Chances are your camera won’t have sufficient dynamic range to capture both.

In this case, you can combine multiple exposures one for the moon, one for the foreground (but please – don’t cheat and paste the moon in where it “looks good” ;) ).

Alternatively, find an object to silhouette against the darkening sky and expose just once for the moon. I like this approach as it keeps things real and avoids messing about combining exposures in post-production (although many people enjoy that, I know!).

There’s still time for a practice run at your planned location this evening here in the US – if you can, head out to scout things out on the ground. Tomorrow, be sure to devote some time to a mental rehearsal of the shots you want to capture. And of course, double check the points in this post!

Wishing you all a spectacular “Blood Supermoon”!