xy2sky(1)

🌸 xy2sky — the "where tf is this pixel actually" tool 🌸

okay bestie, you're looking at the xy2sky(1) page from the General Commands Manual 💅 and honestly? she's an icon. let's get into it.

✨ Name ✨

xy2sky — compute RA Dec from X Y using WCS in FITS and IRAF image files 🦋

✨ Synopsis ✨

xy2sky [-vbjg] [-n ndec] file.fts x1 y1 ... xn yn

or

xy2sky [-bdjgv] [-n ndec] file.fts @listfile

✨ Description ✨

so. xy2sky — pronounced X-Y-to-sky, yes really, that's the vibe — is a little utility that gets you the world coordinates of a bunch of image coordinates in a FITS or IRAF image. 🌈

the World Coordinate System (WCS) info sitting in the image header describes, in a standard way, how sky coordinates and image pixels relate to each other. this program takes that info and uses it to transform image coordinate (X,Y) pairs into right ascension and declination sky coordinate pairs. it's giving translator. it's giving glow-up from pixels to sky. 💫

the current version of the program prints the coordinates at the same equinox as is given in the image header, but future versions will allow transformations to B1950/FK4, J2000/FK5, or galactic coordinates. and input and output files in the Starbase format will eventually be allowed too — we're manifesting it. 🕯️✨

✨ Options ✨

• -a — append the input line after the output position 📎
• -b — B1950 (FK4) output
• -d — RA and Dec output in degrees 📐
• -e — output in ecliptic longitude and latitude, in degrees
• -f <number> — set the third dimension for 3-D projections such as CSC 🧊
• -g — galactic longitude and latitude output 🌌
• -i — first column is star id; 2nd and 3rd are the x,y position 🏷️
• -j — J2000 (FK5) output
• -m <number> — set the mode for output of LINEAR WCS coordinates: 0: x y linear, 1: x units y units, 2: x y linear units units 🎚️
• -n <number> — number of decimal places in the output RA seconds 🔢
• -q <year> — output equinox if not 2000 (-j) or 1950 (-b) 📅
• -t — output as a tab-separated table 📊
• -v — more descriptive output 💬
• -z — use AIPS classic projections instead of WCSLIB 👑

✨ See Also ✨

sky2xy(1) — the reverse queen, go say hi 🫶

✨ Author ✨

Jessica Mink, SAO (jmink@cfa.harvard.edu) 💖

lowkey a whole legend. no cap.

and that's the page!! this was WCSTools, dated 6 July 2001 — yeah she's vintage but she still ate, fr fr. 💜👑 bye bestie, go convert some pixels 🎀