HDW 3
Hartl-Dengel-Weinberger 3 (HDW 3) is an extremely faint ancient planetary nebula in the constellation Perseus. It is so faint that it is very rarely imaged.
The progenitor star is the small blue star just barely visible immediately below the large orange star in HDW 3. The progenitor is not, as one would expect, in the centre of the nebula. This is because it is moving rapidly in a northwesterly direction. It is moving through a dense area of interstellar medium (ISM). This ISM is slowing down HDW 3, creating a shock front and the unusual "braided" appearance. As the star isn't slowed by the ISM it has continued to move and is thus no longer at the centre of HDW 3 and is slowly overtaking HDW 3. This causes the shock front to be brighter as it's getting more ultraviolet radiation, whereas the opposite side of HDW 3 is getting less UV radiation and has become invisible. This movement of the star causes differential excitation of the shell. OIII emission, which requires higher energy of the ionizing radiation than HII emission, only happens close to the star.
The progenitor star is the small blue star just barely visible immediately below the large orange star in HDW 3. The progenitor is not, as one would expect, in the centre of the nebula. This is because it is moving rapidly in a northwesterly direction. It is moving through a dense area of interstellar medium (ISM). This ISM is slowing down HDW 3, creating a shock front and the unusual "braided" appearance. As the star isn't slowed by the ISM it has continued to move and is thus no longer at the centre of HDW 3 and is slowly overtaking HDW 3. This causes the shock front to be brighter as it's getting more ultraviolet radiation, whereas the opposite side of HDW 3 is getting less UV radiation and has become invisible. This movement of the star causes differential excitation of the shell. OIII emission, which requires higher energy of the ionizing radiation than HII emission, only happens close to the star.
Imaging telescope: Takahashi FSQ130ED
Imaging camera: ASI 2600mm
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: QHY 5 II
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon Ha (3nm), Astrodon OIII (3nm).
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius, RB Focus Excalibur.
Dates: 21st. Jan - 20th. Feb 2024
Frames:
Astrodon Ha 144 x 600'
Astrodon OIII 78 x 600'
Astrodon R,G & B 3 x 30 x 120'
Total integration = 40 Hours
Center (RA, Dec): (51.577, 45.389)
Center (RA, hms): 03h 26m 18.487s
Center (Dec, dms): +45° 23' 21.799"
Size: 59.8 x 41.9 arcmin
Radius: 0.608 deg
Pixel scale: 1.2 arcsec/pixel
Orientation: Up is 358.6 degrees E of N
Imaging camera: ASI 2600mm
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: QHY 5 II
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon Ha (3nm), Astrodon OIII (3nm).
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius, RB Focus Excalibur.
Dates: 21st. Jan - 20th. Feb 2024
Frames:
Astrodon Ha 144 x 600'
Astrodon OIII 78 x 600'
Astrodon R,G & B 3 x 30 x 120'
Total integration = 40 Hours
Center (RA, Dec): (51.577, 45.389)
Center (RA, hms): 03h 26m 18.487s
Center (Dec, dms): +45° 23' 21.799"
Size: 59.8 x 41.9 arcmin
Radius: 0.608 deg
Pixel scale: 1.2 arcsec/pixel
Orientation: Up is 358.6 degrees E of N
Sky Map & Finding Chart
Ha, OIII and RGB in the image. (These are rotated 180° from the final image) - click on image for slightly larger view.
Annotated Image
