What can I image tonight?

Find a target that fits the time and sky you have tonight. Set your location and telescope, then compare the available observing window with the model's estimated imaging time.

Check the location shown below first: until you set one, the planner uses a rough guess from your browser's time zone. Cloud, nearby buildings and trees are not included. The results are a starting plan to check against the conditions outside.

Use the result

1. Check the window. Read when the target clears your altitude limit and whether the Moon changes the useful part of the night. Times use this device's time zone.
2. Choose a target marked Fits. Its predicted integration time leaves some room inside the available window. Check that the object also fits the telescope's frame.
3. Open the target's page. Compare sky classes and sub lengths there. If you capture it, the feedback buttons let you report whether the model's estimate matched.

Work through one target Compare telescope options

Keep the session going

Try a shorter target first if the window is tight. Spare power can extend a battery-limited session; it cannot create more darkness or clear a blocked horizon.

Check Seestar S50 accessories · When EQ mode helps · Plan next month’s targets

How it decides

• Dark means the Sun below −18°, astronomical darkness, which is when faint nebulae and galaxies are worth the integration. Star clusters and planetary nebulae are already worth shooting in nautical twilight, so they get the wider window either side. In high-latitude summer neither happens; the planner falls back to −12° and then −6°, and says which it used.
• Above your limit is the longest continuous run the target spends above the chosen altitude inside that window. Altitude is not just a horizon check: the time each target needs allows for the air its light comes through, so the same object costs more low in the south than overhead. Below 30° you are looking through twice the atmosphere and the brightest part of the skyglow.
• The Moon adds skyglow while it is up: roughly one Bortle class at first quarter, two at a bright gibbous, three at full. If the Moon is up for most of a target's window the time is worked out for the brighter sky. The headline says how much of the dark it leaves moonless, which is the figure that decides whether a night is worth carrying a telescope outside for.
• In frame is how much of the scope's short side the target covers. Something filling a twentieth of the frame is a night spent photographing background sky, and something twice the frame across needs a mosaic or a chosen corner.
• Variety. The list is ranked on how comfortably each target fits the night, but no more than three of any one kind come first: in Cygnus in August a pure ranking is eight open clusters.
• Solid image needs is the calculator's per-pixel SNR 6 figure with the recommended filter and the scope's default sub length. "Fits" means it needs under 80% of the window; "Tight" up to 120%; "Start it" up to three such nights, since every night's subs stack.
• Positions are computed to a fraction of a degree, good enough for planning. Times are shown in this device's time zone, so planning a trip from home shows home time. Your coordinates stay in your browser.

Pick a target from the list to open its page for your scope, with the full Bortle table and sub-length comparison. Or use the calculator for a single object.