Is full frame or a crop sensor better for astrophotography?

Full frame generally has the advantage for astrophotography, mainly through greater total light-gathering area and typically better high-ISO noise performance at a given sensor-technology generation — but the gap narrows once you're comparing equivalent framing rather than the same real focal length, since APS-C needs a shorter real lens to match a full-frame field of view, and that shorter lens comes with its own real astro-shutter-speed benefit.

The Framing-Matched Comparison

Matching a full-frame 24mm field of view needs roughly a 16mm lens on APS-C. Under the 500 rule, that works out to roughly 20 seconds on APS-C against roughly 21 seconds on full frame — genuinely close. Under the NPF rule with a same-resolution 24-megapixel sensor on each format, APS-C's tighter pixel pitch (roughly 3.9 microns against full frame's 6.0) shortens its figure to roughly 13.5 seconds against full frame's roughly 12 seconds — also close, and not decisively in full frame's favor the way total light-gathering area alone might suggest.

Where Full Frame's Real Advantage Actually Shows Up

The meaningful full-frame edge comes from total light-gathering area and per-generation sensor technology, which drives cleaner shadows and better dynamic range at the high ISOs astro work commonly needs — not primarily from the shutter-speed math, which lands closer between the two formats than photographers often assume. A crop-sensor body with a genuinely fast, well-corrected wide lens can produce excellent astro results; it isn't a second-tier choice the way it might be assumed to be from format reputation alone.

Compare your own specific cameras and lenses directly in the Astro 500/NPF Rule Calculator, pre-filled with the APS-C equivalent framing.