obrazell
August 18th, 2024, 12:46 PM
For this OOTW I am choosing the other NGC planetary nebula in Lyra in NGC 6765.
I am surprised that it has not been included as an OOTW before. NGC 6765 was first
discovered by Albert Marth using William Lassell’s 48” speculum metal mirror
telescope in 1864 and then independently rediscovered by Truman Safford in 1870
and then again by Stephan in 1888. It was not recognised as a planetary nebula until
1946 when Minkowski observed that it had an emission line spectra from plates taken
with an objective prism on the 10” Bruce Astrograph at Mt Wilson, although this
maybe questionable as the 10” Bruce went back to Yerkes after Barnard had finished
with it and never came back to Mount Wilson. Mt Wilson did have a similar telescope
which I thought was a Cooke astrograph. Perhaps surprisingly there does not seem
to have been much research done on the nebula itself, although it is suggested that it
is in the early stages of an interaction with the local ISM. The classification given here
is WZO1. There has been a certain amount of research done on the central star as it is
a rare type of star known as a PG 1159 star. These are hydrogen deficient stars in the
transition between CSPN and white dwarfs. The central star currently has a temperature
of around 93000K. They are also very short period variables. NGC 6765 is thought to lie
at a distance of perhaps 9400 light years, GAIA gives 3476 pc. It is also suggested that
the nebula is about 8000 years old, but with large error bars. The nebula itself has a
bipolar structure looking like a much fainter version of M76 with a bar and then handles.
A fine amateur image can be found at http://www.astrophoton.com/NGC6765.htm.
There is also an outer loop in this image which maybe part of the interaction with the ISM.
5508
I was surprised that it had not made it into the venerable WSDSH Vol. 2
My initial observations of this nebula using my old 20” Obsession showed only the faint
streak but the use of an OIII filter brought out some of the handles and that fact that
the bar was not uniform. It is another nebula where what you see is very dependent on
the sky conditions at the time. For various reasons I have not tried it yet wit the 15".
Anyway as always give it a go and let us know what you find.
I am surprised that it has not been included as an OOTW before. NGC 6765 was first
discovered by Albert Marth using William Lassell’s 48” speculum metal mirror
telescope in 1864 and then independently rediscovered by Truman Safford in 1870
and then again by Stephan in 1888. It was not recognised as a planetary nebula until
1946 when Minkowski observed that it had an emission line spectra from plates taken
with an objective prism on the 10” Bruce Astrograph at Mt Wilson, although this
maybe questionable as the 10” Bruce went back to Yerkes after Barnard had finished
with it and never came back to Mount Wilson. Mt Wilson did have a similar telescope
which I thought was a Cooke astrograph. Perhaps surprisingly there does not seem
to have been much research done on the nebula itself, although it is suggested that it
is in the early stages of an interaction with the local ISM. The classification given here
is WZO1. There has been a certain amount of research done on the central star as it is
a rare type of star known as a PG 1159 star. These are hydrogen deficient stars in the
transition between CSPN and white dwarfs. The central star currently has a temperature
of around 93000K. They are also very short period variables. NGC 6765 is thought to lie
at a distance of perhaps 9400 light years, GAIA gives 3476 pc. It is also suggested that
the nebula is about 8000 years old, but with large error bars. The nebula itself has a
bipolar structure looking like a much fainter version of M76 with a bar and then handles.
A fine amateur image can be found at http://www.astrophoton.com/NGC6765.htm.
There is also an outer loop in this image which maybe part of the interaction with the ISM.
5508
I was surprised that it had not made it into the venerable WSDSH Vol. 2
My initial observations of this nebula using my old 20” Obsession showed only the faint
streak but the use of an OIII filter brought out some of the handles and that fact that
the bar was not uniform. It is another nebula where what you see is very dependent on
the sky conditions at the time. For various reasons I have not tried it yet wit the 15".
Anyway as always give it a go and let us know what you find.