IMMATCH(1)

💖 IMMATCH — the matchmaking era 💖

okay so bestie, pull up a chair 🪑✨ this one is immatch, and it lives in section 1 of the user commands manual (the "stuff you type at a shell" section, iykyk). Her whole thing? AME. That's the name, that's the gig, that's the vibe. 👑

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✨ SYNOPSIS ✨

[-vl] [-m mag] [-n frac] [-s mode] [-g class] [-h maxref] [-i peak]

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🌸 DESCRIPTION 🌸

so what does she do, you ask? 🦋 she matches a catalog to the stars she finds in your image, using the WCS baked into the image file. literally the glow-up pipeline from "random pixels" to "I know exactly which star you are."

here's the fuller shape of the invocation, no cap:

[-c catalog] [-p scale] [-b ra dec] [-j ra dec] [-r deg] [-t tol]
[-x x y] [-y frac] FITS or IRAF file(s)

and now the flags, one by one, because we do not skip 💅:

• -a ang — initial rotation angle in degrees (default 0)
• -b — initial center given as B1950 (FK4) RA and Dec
• -c cat — the reference catalog (gsc, uac, ujc, tab table file
• -d cat — use the following DAOFIND output catalog instead of doing a search
• -f — write the output as X Y RA Dec, instead of N RA Dec X Y
• -g num — Guide Star Catalog class (-1=all, 0, 3 (default -1
• -h num — maximum number of reference stars to use (10-200, default 25
• -i num — minimum peak value for a star in the image (<0=-sigma)
• -j — initial center given as J2000 (FK5) RA and Dec
• -k — which magnitude to use (1 to nmag)
• -l — reflect left<->right before rotating and fitting
• -mx m1[,m2] — initial reference catalog magnitude and limits
• -p num — initial plate scale in arcsec per pixel (default 0)
• -q — fit the image to catalog magnitude polynomial(s)
• -r ang — rotation angle in degrees before fitting (default 0)
• -s frac — use this fraction extra stars (default 1.0)
• -t tol — offset tolerance in pixels (default 20)
• -u num — USNO catalog single plate number to accept
• -v — verbose
• -w — rotate the image WCS with the image
• -x x y — X and Y coordinates of the reference pixel (default is center)
• -y num — multiply image dimensions by this for the search (default is 1)
• -z — use AIPS classic projections instead of WCSLIB

heads up bestie 🫶 if you're coming from the synopsis and wondering about -m mag, -n frac and -s mode — those are hanging out up there in the usage line, and -s shows up down here as frac. just the way she's written. copy it exactly, don't freestyle. 🎀

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and that's the whole page, fr fr. she's short but she's doing a LOT. 🌈

source/version: immatch EB_SOURCE · February 2026 — go match some stars, you absolute icon 👑💜