How to Use the Milky Way Field Guide
Pick Milky Way targets for your site and night, then download a printable PDF shot pack with aim, timing and exposure for each one.
Open the Milky Way Field Guide
What this tool answers
- Which parts of the Milky Way are up from my site at the time I plan to shoot?
- Which way do I point, how high, and when does each target peak?
- What shutter speed and ISO should I start with on a tripod or a star tracker?
What you see on the screen
- Download a printable PDF: a banner with the number of selected targets and a Download PDF button (on a phone it also sits in a bar at the bottom).
- Bright sky at this site: a notice shown only at Bortle 7 or brighter.
- Tonight conditions: Moon phase, percent lit, rise and set, clouds, and the Dark window.
- Setup: Location (ten Guyana towns), Date, a Preview time slider in 5 minute steps, Camera, Focal length (mm) and Aperture (f/).
- Target previews: seven target cards in three groups, with your field of view ("FOV") in degrees.
- Download PDF: an I have a star tracker box, an ISO hint box (1600 by default) and the download button.
Arrive from the Milky Way Season Planner with Open field guide and the setup is already filled in.
Step by step
- Check Location, Date and Preview time in Setup.
- Set Camera, Focal length (mm) (8 to 600) and Aperture (f/) (1 to 22).
- Choose targets. Tap a card to include or exclude it, or use Balance pack, Select all (7), Clear, or a group button.
- Tap Jump preview to peak on a card to move Preview time to that target's highest point.
- Tick I have a star tracker if you use one, and set ISO hint.
- Tap Download PDF. The file is named for the site and date.
- On site, take a short test frame and adjust. The exposures are rules of thumb.
The real Milky Way Field Guide on the evening of 6 October 2026: tonight's Moon and dark window, the target cards, the Large Magellanic Cloud's peak, and the PDF shot pack.
How to read the results
Target cards come in three groups: Bulge & summer core (Galactic Core, Rho Ophiuchi), Northern & winter arch (Cygnus, the Galactic Anticenter, the winter Milky Way in Orion) and Southern & Magellanic (the two Magellanic Clouds). Each card shows a sky preview aimed at the target, AZ and ALT at the preview time, and an Above horizon or Below horizon tag. A timing line covers that night's longest moonless dark stretch, in Guyana time. When the target crosses the meridian inside the stretch, it reads "Culminates near" with the time and altitude. When it is still climbing as the stretch ends, or already past its highest, it reads "Highest while moonless" and adds the true culmination when that falls inside astronomical night. For example, on 6 October 2026 from Georgetown the Large Magellanic Cloud is highest while moonless at 12.6° at the 03:01 moonrise, and culminates at 13.5° at 04:12. The line ends with the hours the target spends above the horizon in the stretch. The Magellanic Cloud cards show a Photo plate (a reference photograph), not a simulated sky.
Balance pack picks the core, Rho Ophiuchi, Cygnus and both Clouds, keeping those above the horizon at the preview time (all five if none are up).
The seven target cards on the live sky for Georgetown or Lethem: AZ and ALT at the preview time, each target's peak, and what the Balance pack would pick.
Tonight conditions gives Moon rise and set and the Dark window for your date, in Guyana time (America/Guyana, UTC-4). The cloud figure is the live forecast for the coming night, and Best clouds is the clearest stretch in the 7 day forecast; neither follows the date you pick.
Preview time uses local solar time from longitude: about 7 minutes ahead of Guyana clocks at Georgetown, under a minute at Lethem.
The PDF is Letter size. The cover lists site, time, gear, sky brightness, mount, suggested exposure, Moon, weather and dark window. Each target page has a sky picture and rows for Aim (bearing, altitude and FOV), Timing, Exposure, Drift and Conditions.
On a tripod, the Exposure row uses the NPF rule, (35 × f-number + 30 × pixel pitch in µm) ÷ focal length, capped at 30 s and rounded down to a standard shutter speed: 10 s for the default Sony A7 III at 24 mm and f/2.8. On a tripod, Drift is LOW up to 24 mm full-frame equivalent, MEDIUM up to 50 mm and HIGH above that. With a tracker ticked, it gives a range instead: 30 to 92 s for the same setup. Compare with the NPF / Spot Stars Calculator.
The shot pack's Exposure and Drift rows for your camera, lens and mount, with the NPF sum worked out.
On a tripod with the default Sony A7 III, which lens makes the Field Guide's Drift row read HIGH?
- 14 mm
- 24 mm
- 35 mm
- 85 mm (the right answer)
On a tripod the Drift row reads HIGH above 50 mm full-frame equivalent; 35 mm reads MEDIUM and 24 mm or wider LOW.
Using it from Guyana
- The galactic core crosses due south at 54° from Georgetown and 58° from Lethem.
- The Magellanic Clouds stay low. The Large Cloud peaks at 13.4° and the Small Cloud at 10.4° from Georgetown (16.9° and 13.8° from Lethem), both due south.
- In dark hours the Large Cloud reaches that height from about October to February, the Small Cloud from about August to December: good targets for November to January, when the core is down.
- You need an open southern horizon for them.
- At Bortle 7 or brighter, previews and PDF pictures switch to a Bortle 2 simulation, the text keeps your real class, and a "Try a darker site" row offers Lethem, Bartica and Mahdia. See Dark Skies in Guyana.
How high each Magellanic Cloud climbs in full darkness, month by month, from Georgetown or Lethem.
The Field Guide's two reference photographs of the Magellanic Clouds.
It is mid-December and the core is down. Which Field Guide targets suit the night from Guyana?
- The galactic core and Rho Ophiuchi
- The Magellanic Clouds and the winter Milky Way (the right answer)
- None: the Milky Way is gone until February
- Only Cygnus, high overhead
From November to January the core is too close to the Sun, but both Clouds reach their highest in dark hours, low in the south, and the winter Milky Way through Orion is up.
What it does not do
- It has no GPS and no box for your own coordinates.
- It has no Bortle or Moon switches; the Season Planner has those.
- It does not score nights. Use the Season Planner to choose the night first.
- It does not check your local horizon.
Common mistakes
- Downloading the PDF with a target marked Below horizon and expecting to shoot it at that time.
- Reading the cloud line as the forecast for a date weeks away.
- Using a long lens on a tripod. Watch the Drift row.
- Skipping the test frame.