The Tadpole galaxy:

North is up (exact, mirrored). 0.53 "/pixel [18.8' x 7.4'] FWHM = 4.2"

This galaxy has a massive (and rather bright) tidal tail, but I can't see an obvious companion galaxy. The general consensus is that there's a second galaxy behind it... although a nearby elliptical has a suspiciously similar redshift:

Total exposure time: 364 * 30 seconds = 3 hours.

Used in stack: 165 * 30 seconds = 1.3 hours.

Telescope: C9.25 (230mm, f/10, fl=2300mm) + 0.63 Starizona reducer

Camera: IMX533 (16mm diagonal, square, color)

Processing:

1. Callibration (dark + flat)

2. Stacking (average w/ outlier rejection)

3. White balance and background subtraction (no gradient removal)

4. Asinh stretch (color preserving)

5. Rotation + crop

6. Tone curve

Not my finest work due to some patchy clouds, but not terrible.

Related:

• /astro/arp188/stacked.fits.fz: Raw stacks

• ned.ipac.caltech.edu/level5/Arp/Figures/big_arp188.jpeg: Arp's image