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Everything worth a look from your sky, best pick first; tap a target for its night and settings.

How the numbers are worked out

Events. Once a week a script computes the next 60 days () in Universal Time: transits, moon events, comets and asteroids. Your browser then works out altitude, darkness and the Moon for your location. This page makes no calls to any data service on its own (the site counts visits with Cloudflare's cookieless Web Analytics: no cookies, no trackers, no ads); two buttons do, and only when you press them: the Seestar QR button sends that night's plan to ZWO's server, and Add weather sends your city's rounded position to our weather service.

What makes the list. These are hard cuts; anything that fails one is hidden while "Hide what I can't see" (in Explore's filters) is on, and shown with the reason when it is off.

Exoplanet transits: dark enough (Sun 12° down), the star above 30° throughout and 40° at mid-transit, with 30 minutes of sky on each side, and a dip at least 3 times the scatter we expect from your telescope.
Comets and asteroids: on each night, when the object stands highest in a dark sky above 25° for at least half an hour, and brighter than your reach after allowing for moonlight. Magnitudes are JPL predictions; comets often run a magnitude or more brighter or fainter than predicted.
Jupiter's moons: Jupiter at least 15° up with the Sun at least 6° down, and the event large enough at your telescope's pixel scale; the times are the part of each event you can watch.
Eclipsing binaries: minima with the star 30° up and the Sun 12° down for the whole recording window, on stars bright enough to time (the rules are with the eclipsing-binary list).
Variable stars: AAVSO's own requests that ask for B, V or R (your camera's blue, green and red), with the star 30° up for half an hour of dark sky and bright enough at its brightest for your telescope to measure.
Galaxies, nebulae and star clusters: OpenNGC objects at least 30° up for an hour of dark sky on their best night in the range, large enough to show at your pixel scale; each carries a framing verdict for your field and a suggested integration (summarized on each target).
Supernovae: recent, spectroscopically classified supernovae bright enough for your reach and high enough in a dark sky. Their magnitudes change daily; each one shows its latest measurement and its date.

The chance and its label come from one model for every type: how far your telescope's signal clears what a usable result needs (a dip 3 times its scatter, a comet or asteroid detected, a variable measured to about 0.1 mag, a Jupiter event seen at your pixel scale), then what your sky, the altitude, twilight, the Moon, a pass near the zenith and a typical backyard horizon do to it, and for a transit the chance its timing falls inside your run. Easy means a 70% chance or better, Moderate 40% or better. Weather is not part of it. "Quick session" keeps targets that need an hour or less; "Done by" keeps those you can finish by that hour.

Transit timing comes from ExoClock ephemerides where they exist, built for exactly this kind of small-telescope work, and from the NASA Exoplanet Archive otherwise, corrected from the Sun's frame of reference to Earth's (up to 8 minutes). The listed time uncertainty is what the published ephemeris error grows to by that date; real transits can drift further.

Transit precision comes from a simple scatter model built from our own Seestar S30 Pro data. Each 10 s frame has three kinds of scatter: the atmosphere's twinkle ( for a 30 mm telescope), the star's own photon noise for your filter, and the sky's glow. These are scaled to your aperture, the star's brightness and its altitude, with a frame every 11.5 s as the Seestar app delivers them (19.3 s under N.I.N.A.), and the result is multiplied by 1.6 to cover what the simple terms miss, such as drift and imperfect comparison stars. On our HD 189733 b night (S30 Pro, dual-band filter, October 2, 2026, 19.3 s frames) the model predicts a depth uncertainty of ±0.37%; we measured a depth of 2.50% with an uncertainty of ±0.34%. That is not an independent test, because the twinkle and the 1.6 factor were measured on the same night; treat the dip-versus-scatter figures as rough.

Reach (the faintest star 20 minutes of exposure shows clearly) is built from single 10 s frames on our S30 Pro at a dark site with no Moon: magnitude 13.7 through the clear filter and 12.1 through the dual-band filter. Stacking gains 1.02 magnitudes for every tenfold increase in exposure, as measured on a Seestar S50 night (1 to 480 frames), giving 15.8 and 14.2 for 20 minutes on a 30 mm telescope. Other telescopes are scaled by aperture only, not measured. Your sky choice shifts reach by half a magnitude for each magnitude of sky brightness, counted from that dark site; half a magnitude is the textbook rate for a sky-limited stack (our short dual-band frames measured 0.28, because at a dark site they are partly limited by the camera's read noise), and the brightness behind each choice is approximate. Moonlight takes up to 0.7 magnitudes at full Moon, more when the Moon is close to the target, fitted to three pairs of our nights at that dark site; under a bright sky it is probably more. Comets need to be about 3 magnitudes brighter than a star, because their light is spread out.

Which filter. Each target carries the filter we recommend for it, and its chance is worked out with that filter. Stars and other points of light (transits, eclipsing binaries, variable stars, asteroids, supernovae), comets, galaxies and star clusters get the clear filter: on our S30 Pro the dual-band filter cost 1.77 magnitudes of starlight and did not darken our dark-site sky enough to make up for it, so the clear filter reached about 1.6 magnitudes deeper. At a city site that comparison is not measured yet, and the pill says so rather than switching. Emission and planetary nebulae and supernova remnants get the dual-band filter, which keeps their light while cutting sky glow, more so under a bright sky or with the Moon up (our judgment, not measured). Jupiter gets the clear filter in planet mode. Explore's filters can show the targets for one filter, for a night spent on one.

Sky brightness for your city. When you pick a city, the sky choice starts from a light-pollution atlas: the modeled zenith brightness at the city's center, converted to magnitudes per square arcsecond, then matched to the nearest step. It is a model of 2014 lighting, not a measurement of your site: it tends to make rural places look too dark and today's city evenings look too dark as well, and your own yard may differ by a magnitude. Pick a step yourself to override it. Sky brightness from the World Atlas of Artificial Night Sky Brightness: Falchi F., Cinzano P., Duriscoe D., Kyba C.C.M., Elvidge C.D., Baugh K., Portnov B.A., Rybnikova N.A., Furgoni R. (2016), The new world atlas of artificial night sky brightness, Science Advances 2(6):e1600377, doi:10.1126/sciadv.1600377; data: Supplement to: The New World Atlas of Artificial Night Sky Brightness, GFZ Data Services, doi:10.5880/GFZ.1.4.2016.001, licensed CC BY-NC 4.0 (non-commercial use only). Changed by SkyCruncher: sampled at each city's coordinates and converted to total zenith brightness in mag/arcsec².

Jupiter's moon events are computed from JPL Horizons positions of the moons relative to Jupiter; we checked them against Horizons' own eclipse and occultation flags and they agree within 1 to 3 minutes.

Your location. The city search runs inside your browser against a list of the world's cities and larger towns (from GeoNames), which downloads from this site. What you type is never sent anywhere. The city's center sets the location and its time zone sets the times; your nearest listed city is close enough for this planner. Until you pick a city, the page starts from the largest listed city in your device's time zone and says that it is a guess; if your time zone is not in the list, it asks for your city instead. Your last choices are remembered in this browser only.

Updated this week. Guidance, not prediction: weather, local horizon, light pollution and firmware all matter more than these rankings.

Your telescope, as the planner sees it

Rare events in your calendar

A calendar of the rarer events we list (at most 20, rebuilt every week) that your calendar app keeps up to date: Subscribe to rare events

In Google Calendar: Other calendars, +, From URL, paste the link.

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