Stacking Starlight

When plate solving fails or can't find the target

If your software can't solve the image — "no match," wrong position, or it never converges — the solver almost always lacks one of three things: the right **scale**, a usable **star field**, or the correct **index data**. Work through them in order.

1. Triage the failure

  • "No solution / no match" → scale or index-file mismatch (most common). Keep reading.
  • Solves but to the wrong place → bad initial coordinates or a flipped/mirrored image.
  • Solves then GoTo lands off-target → sync/centering or mount-model issue, not the solver.

2. Diagnose and fix

  • Set the pixel scale right. Give the solver your real arcsec/pixel (from camera pixel size +

focal length, including reducer/barlow). A wrong scale is the #1 cause of failed solves; a generous

scale range helps blind solves.

  • Give it enough stars. Too short an exposure or heavy light pollution yields too few detectable

stars. Lengthen the solve exposure, focus first (a wildly out-of-focus frame won't solve), and

avoid solving on the Moon or thick cloud.

  • Install the right index files for your field of view (small FOV needs the finer index series).

Missing/wrong-scale indexes make blind solves fail outright.

  • Handle flips/binning: make sure image orientation/binning matches what the solver expects, and

feed approximate RA/DEC to enable a fast nearby solve instead of a full blind search.

3. Verify

A good solve returns plausible RA/DEC, scale, and rotation matching your setup. After a sync, confirm

a GoTo centers the target — if it solves but doesn't center, that's a mount/sync issue, not the

solver.

When it isn't the solver

If frames won't solve because stars are bloated or distorted, fix imaging first — see

holding focus and

distorted star shapes.

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How plate solving works: plate solving explained.