* Astronomy

NGC 6644 (also PK 8-7.2, HD 170839, Hen 2-408 and ESO 522-PN33) is a magnitude +10.7 planetary nebula located in the constellation Sagittarius. 
The central white dwarf star has an apparent magnitude of +15.9

The planetary nebula was discovered by American astronomer Edward Charles Pickering using a 38.1 cm (15 inch) refractor at the Harvard College Observatory on the 13th July 1880.

Right Ascension 18h 32m 34.7s, Declination -25° 07' 42"