obrazell
February 2nd, 2025, 08:40 AM
Haro 3-75
PN G193.6-09.5
Orion
R.A.: 05h40m45.0s
Dec.: +12°21'23" (2000)
Magnitude: 13.90
Size: 24"
There are many objects of interest in Orion and the main focus for observers is naturally
the star forming regions around M42 and M78. Orion does however contain a number
objects at the other end of the stellar evolutionary scale with a number of challenging
planetary nebulae. The well-known ones include the popular ones such as NGC 2022
and J320 and there are a number of the more challenging Abell planetary nebulae in
Orion as well such as Abell 10 and Abell 12. There is however a slightly brighter target
than the Abell nebulae in the overlooked planetary nebula Haro 3-75 at the top of Orion.
5645
PanStarss image
First discovered on plates aimed at discovering H-Alpha emission line objects in the star
forming regions of Orion and Taurus by Guillermo Haro in 1953 it was not initially recognised
as a planetary nebula and it took until 1964 before Mayall identified it as such. Interestingly
despite the survey being setup to discover H-Alpha strong YSO’s, undertaken using an
objective prism on the Schmidt telescope at the Tonantzintla observatory in Mexico. The
spectra of H 3-75 is very weak at H-Alpha and much stronger in the OIII lines.
Haro 3-75 lies in the outer regions of our galaxy opposite to the galactic centre at a
distance of perhaps 3700 kpc from us, although there seems to be quite a large range in
distances quoted from 4.3 kpc down to perhaps 2.8 kpc. The central star is also of
interest as it is probably a binary system. The spectral type of the central star is also
odd in that it is very cool for a planetary nebula with a spectral type given as G-K
and there are suggestions that this maybe a born again red giant nucleus
similar to Sakurai’s Object (V4334 Sgr). H 3-75 is classified as a compact high excitation
nebula with a ring structure according to HASH
5644
- Image courtesy of Ian Smith
Lying at the top of Orion near the Taurus border Haro 3-75 sports a 25” disc and although
it is faint it has been reported in telescopes as small as 8” (20cm) from high altitude sites.
There are UK observations with a 16” telescope and it may well be visible in smaller
telescopes on a very clear night. Reports suggest that it responds well to both UHC and OIII
filters. Due to its small size I would suggest using a medium to high power eyepiece when
trying to find this object. It is not clear if the central star is visible or if the apparent spot is
just the brighter core of the nebula. My own observations with a 22” from a low lying site in
the UK say that it was not that difficult and showed a small disk when using an OIII filter.
There is an interesting amateur image at https://www.imagingdeepspace.com/h-3-75.html
showing a lot of structure in the disk and an extended non symmetrical outer halo
PN G193.6-09.5
Orion
R.A.: 05h40m45.0s
Dec.: +12°21'23" (2000)
Magnitude: 13.90
Size: 24"
There are many objects of interest in Orion and the main focus for observers is naturally
the star forming regions around M42 and M78. Orion does however contain a number
objects at the other end of the stellar evolutionary scale with a number of challenging
planetary nebulae. The well-known ones include the popular ones such as NGC 2022
and J320 and there are a number of the more challenging Abell planetary nebulae in
Orion as well such as Abell 10 and Abell 12. There is however a slightly brighter target
than the Abell nebulae in the overlooked planetary nebula Haro 3-75 at the top of Orion.
5645
PanStarss image
First discovered on plates aimed at discovering H-Alpha emission line objects in the star
forming regions of Orion and Taurus by Guillermo Haro in 1953 it was not initially recognised
as a planetary nebula and it took until 1964 before Mayall identified it as such. Interestingly
despite the survey being setup to discover H-Alpha strong YSO’s, undertaken using an
objective prism on the Schmidt telescope at the Tonantzintla observatory in Mexico. The
spectra of H 3-75 is very weak at H-Alpha and much stronger in the OIII lines.
Haro 3-75 lies in the outer regions of our galaxy opposite to the galactic centre at a
distance of perhaps 3700 kpc from us, although there seems to be quite a large range in
distances quoted from 4.3 kpc down to perhaps 2.8 kpc. The central star is also of
interest as it is probably a binary system. The spectral type of the central star is also
odd in that it is very cool for a planetary nebula with a spectral type given as G-K
and there are suggestions that this maybe a born again red giant nucleus
similar to Sakurai’s Object (V4334 Sgr). H 3-75 is classified as a compact high excitation
nebula with a ring structure according to HASH
5644
- Image courtesy of Ian Smith
Lying at the top of Orion near the Taurus border Haro 3-75 sports a 25” disc and although
it is faint it has been reported in telescopes as small as 8” (20cm) from high altitude sites.
There are UK observations with a 16” telescope and it may well be visible in smaller
telescopes on a very clear night. Reports suggest that it responds well to both UHC and OIII
filters. Due to its small size I would suggest using a medium to high power eyepiece when
trying to find this object. It is not clear if the central star is visible or if the apparent spot is
just the brighter core of the nebula. My own observations with a 22” from a low lying site in
the UK say that it was not that difficult and showed a small disk when using an OIII filter.
There is an interesting amateur image at https://www.imagingdeepspace.com/h-3-75.html
showing a lot of structure in the disk and an extended non symmetrical outer halo