"What should I shoot tonight?" is the question every beginner asks and almost no tool answers well, because the honest answer depends on four things about YOUR night: what's up, where the moon is, what your sky is like, and what your camera actually frames. Run the four questions in order and the sky usually leaves you two or three sensible candidates.
1. What transits mid-evening?
A target is best when it crosses your meridian — its highest point, where you shoot through the least atmosphere. A target transiting at 1 a.m. gives you a full evening of high-quality hours; one transiting at 7 p.m. is already falling into the western murk. As a rule of thumb, the sweet spot each season: galaxies in spring (Markarian's Chain, M81/82, M101), the Milky Way's nebulae in summer (Lagoon, Eagle, the Cygnus complexes), the great showpieces in autumn (Andromeda, Triangulum, the Heart and Soul), and Orion's neighborhood all winter.
Altitude is quality. Below 30° you're imaging through twice the air (airmass 2.0) — softer stars, dimmer signal, worse gradients. Treat 30° as the floor and the hours above it as your real imaging window.
2. Where is the moon?
The moon is a 400,000-km-away flashlight pointed at your sky. Broadband targets (galaxies, reflection nebulae, star clusters) want it below the horizon or under ~30% illuminated and at least 60–90° away. Emission nebulae are the escape hatch: through narrowband filters (Ha especially) you can image them productively under a bright moon that would wash a galaxy out completely. This is why experienced imagers keep both a broadband and a narrowband project running — the moon decides which one gets tonight.
3. Does it fit — and does it fill?
Your field of view is set by focal length and sensor size, and it's brutal arithmetic: Andromeda (3° long) overflows an 8" SCT's field several times over, while a 1′ planetary nebula is a green speck in a camera-lens widefield. Aim for targets spanning roughly 15–75% of your long axis: enough context to compose, enough scale to resolve. Bigger than your field isn't a no — it's a mosaic — but that's a project, not a first pick.
4. Is it bright enough for YOUR sky?
The headline magnitude lies. What matters is surface brightness — how much light per patch of sky — versus how bright your sky already is. A big, low-surface-brightness galaxy (M33 is the famous trap: 'magnitude 5.7' and nearly invisible) needs dark skies or brutal integration time from the suburbs. Emission nebulae under narrowband don't care nearly as much. From a Bortle 7 backyard, the honest beginner list is: bright emission nebulae in narrowband, star clusters, and the handful of high-surface-brightness galaxies (M81, M82, M31's core).
Do it in AstryxTonight's Picks runs all four questions — plus your custom horizon and light-pollution domes — and explains each recommendation. Try it in the demo, no account needed.