Help · Advanced photography
Advanced eclipse photography planning
For those who already have the basics down and want to go after Baily's beads, the chromosphere, or a spot deliberately close to the edge of the path of totality: how to read the lunar limb, what to expect second by second, and how it connects to our tools.
Who this guide is for
If you already know where you'll be on August 12, 2026 and what camera you'll be using, this guide goes a step further: it's aimed at those chasing more than the full eclipsed disc — cleanly resolved Baily's beads, the chromosphere appearing at just the right instant, or a spot chosen on purpose near the edge of the path of totality to stretch out those critical seconds.
It doesn't repeat basic safety or exposure — that's what the Photographer mode help is for; it goes deeper into three phenomena that depend on the Moon's real relief and are measured in seconds, not minutes.
Baily's beads: the photosphere peeking through lunar mountains
Baily's beads are the last flashes of solar photosphere slipping through the valleys of the lunar edge right before C2, and the first ones to reappear right after C3. It isn't a uniform phenomenon: because the Moon's limb has real mountains and valleys, light only gets through where the terrain allows it, so the number of beads, their brightness and their duration change from one location to another and from one eclipse to the next.
That flash is concentrated in a very short window — on the order of ±30 seconds around each contact — so there's no room to improvise your framing on the spot: it helps to know beforehand which arc of the solar limb the string of beads will appear along.
That arc can be predicted from topographic profiles of the lunar limb — built from altimetry instruments like those aboard the LRO and Kaguya/SELENE missions, with a manual-reconstruction legacy that the occultation-observing community associates above all with David Herald's work. A rougher limb along that stretch gives more beads and a longer, more striking sequence; a smooth one gives an almost instant collapse, nearly a single flash.
Our beads simulator uses that same kind of real limb relief — LRO and Kaguya/SELENE topography, not a generic animation — computed for your exact location and the instant of the eclipse: it's the tool for deciding beforehand where to point, available in Photographer mode (PRO Photo / Pass).
How to photograph Baily's beads
Baily's beads are always photographed with the solar filter on. Outside real totality (between C2 and C3) there's still a fragment of photosphere visible, and optically it carries the same weight as the full solar disc in partial phase: the certified ISO 12312-2 filter in front of the lens — the same one you use throughout the partial phase — is exactly what's called for. There's no "beads exception".
With the filter on, the beads come out flat and without flare — that's expected, because the filter dims the whole scene equally (the equivalent of about a 16⅔-stop ND filter, the same reference our exposure calculator uses for this phase). The brighter, halo-like look in many published photos comes from processing and lens optics, not a different safety call: it's worked out in exposure and editing, never by removing the filter early.
The window is measured in seconds, so it pays to have everything decided beforehand: your starting exposure (our calculator derives it from your specific camera), burst shooting with bracketing, and framing already centred on the arc of the limb where the beads will appear.
The chromosphere and chromospheric beads
The chromosphere is the thin layer of the solar atmosphere between the photosphere and the corona: about 2,500 km of real thickness, which at Earth's distance works out to an arc of just 3.45 arcseconds. It's visible for a few seconds right after C2 and right before C3, with its characteristic reddish tone from hydrogen-alpha emission.
During those seconds — and only then, with real totality already underway — the same lunar-limb relief that produces Baily's beads can break that reddish layer up into what's known as chromospheric beads: it's no longer photosphere, so no filter is needed; it's the chromosphere seen through the same lunar valleys, a classic long-telephoto subject the moment totality begins.
It's a brief window within an already brief window: it's worth deciding beforehand whether to spend those first seconds of totality on the chromosphere with a telephoto lens or on a wider shot of the inner corona, because there isn't time for both with the same setup.
Why the exact solar radius matters
The Sun's angular radius isn't a single universal number. The IAU adopts 959.22″ as the reference photospheric value, but much of the eclipse-prediction software out there — including the source that inspired this guide — uses 959.95″, a slightly larger value derived from visible-light limb measurements.
The difference looks tiny, but a slightly larger Sun in the calculation means the Moon covers it for less time: totality duration at a given point can shift by several seconds depending on which solar radius is used, and those seconds are exactly what you're deciding how to split between beads, chromosphere and corona.
In our app, the C1-C4 contacts come from astronomy-engine, which uses the IAU nominal solar radius (695,700 km, ≈959.2″) consistently across every calculation. The source that inspired this guide uses 959.95″ — which is why its totality duration can differ from ours by a few seconds for the same spot. Neither is "wrong": they differ in the adopted reference, which is why you shouldn't mix timings from different sources in your plan.
Exposure: from the formula to your camera
Every phase has very different brightness — from the filtered photosphere to the outer corona there's more than twenty stops of difference — so there's no single setting that works for the whole eclipse. Our exposure calculator derives the shutter speed phase by phase from Fred Espenak's open photometric approach, adapted to your specific camera's aperture, ISO and filter, with ±1-2-stop bracketing as a safety net (the calculator suggests 3 or 5 frames depending on your camera).
If you're shooting with several cameras — one wide-angle for the landscape, another with a telephoto for beads and chromosphere — Photographer mode's multi-camera plan generates a separate exposure table for each setup, so you don't have to do the mental conversion on the spot.
Eye safety: no exceptions, not even for the beads
Eye protection is required at all times except during real totality, between C2 and C3 — this is also what the source that inspired this guide says, in line with NASA's own recommendation. Neither Baily's beads nor the diamond ring are an exception: they still involve visible photosphere, so they're photographed and observed with the same certified ISO 12312-2 solar filter as the rest of the partial phase.
In our app this is a single policy, with no local variants or photographer "tricks": you can read it in detail in the simulator's methodology and in the Photographer mode help.
Sources: NASA — eye safety · Photo Ephemeris — inspiration for this guide · F. Espenak — exposure formula
Frequently asked questions
- Can I take my solar filter off a second before C2 to see Baily's beads better?
- No. As long as any fragment of photosphere is visible — including Baily's beads and the diamond ring — a certified ISO 12312-2 filter is required, both for naked-eye viewing and for photography. The filter only comes off during real totality, between C2 and C3.
- Is the Baily's beads pattern the same everywhere along the path of totality?
- No. It depends on the exact lunar-limb relief visible from your location and the precise instant of each contact, so it changes from point to point along the path — which is why it's worth checking the simulator for your exact location, not a generic one.
- Do I need a different setup for Baily's beads versus the chromosphere?
- It's worth deciding beforehand what to prioritise at each moment: the beads happen in the filtered window right before C2 and right after C3, while the chromosphere — and chromospheric beads — appear in the first and last seconds of totality, already without a filter. With only seconds of margin between phases, it's better to have each setting decided than to improvise it.
- Why doesn't my totality-duration calculation exactly match another source's?
- Probably the reference solar radius: 959.22″ (IAU) versus 959.95″ (common in eclipse-prediction software) can shift totality duration by a few seconds. We compute contacts with astronomy-engine, which uses the IAU nominal radius consistently across the whole app; check which reference the other source uses before assuming an error.