UNGUIDED
CDK20: FL 3454mm, F/6.8, 0.225 arcsec/pixel raw
Imaged 11/13/2021, 11/14/2021, 11/15/2021, 11/19/202, 12/1/2021, 12/2/2021, 12/3/20211
Dengel-Hartl 5 is a large, ancient planetary nebula in Cepheus. It is also designated as PK 111 + 11.1.
It was discovered in 1979 in a survey of Palomar Observatory Sky Survey (POSS) plates (#559) and described in the 1980 Astron. Astrophys. Research Note “A Search for Planetary Nebula on the “POSS””, vol 85, pp 356-358 by J. Dengel, H. Hartl and R. Weinberger. It is designated as DeHt 5.
The blue star in the center of the blue-green OIII-rich region is the central star: UCA3 322:74172 (white dwarf WD 2218+706). Beverly Lynds catalogued the brighter portion as LBN 538 in 1965.
Many PN are circular. The lower portion (below the H-a-rich region near the top of the object) is roughly circular. However, this deep image including that upper region indicates that it has a very unusual shape. It is ~ 9′ EW (up-down) and 7′ NS (right-left), but there is a faint halo extending north (right) beyond the brighter portion of the nebula, increasing the NS apparent size to 11′. DeHt 5 is estimated to be 1300 – 1600 light years distant, making it one of nearest known PN according to Dengel et al. Some reports suggest that the intrinsic morphology of DeHt5 was destroyed in interacting with the interstellar medium (ISM). It is suggested that it has been interacting with the ISM for > 74,000 years. Radio polarization images reveal a long “tail” behind DeHt5 in a direction opposite of the movement of its white dwarf star.
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