Another addition to the collection of planetary nebulae – NGC 6905, also known as the Blue Flash.
It lies in the constellation Delphinus and was discovered by William Herschel in 1784. The central star has a brightness of 14.0 mag and is a white dwarf with quite an interesting characteristic. The distance to the nebula, as with most planetary nebulae, is not well determined, with estimates ranging from 1.7 to 2.6 kpc. The shape of NGC 6905 is characterized by an internal shell with angular dimensions of 47" × 34", along with roughly conical extensions and “antennae”-like formations along the main axis. Apart from the strong oxygen OIII line (which allows for effective narrowband imaging), the nebula's core exhibits one of the broadest OVI emission lines among planetary nebulae. Additionally, OVIII emission has been detected in NGC 6905, and the antennae show intense nitrogen NII emission lines.
The already mentioned central star is an interesting white dwarf with a spectral type of [WO2], meaning its spectrum is similar to Wolf–Rayet stars and is rich in oxygen. Its surface temperature is estimated to be around 150,000 K.
I’ll definitely return to this object with an SA 200 filter to capture its spectrum, so expect a supplementary post illustrating these interesting details
As for the image itself, there were some issues with the stars (the joys of collimating a GSO 10" F/4 and wind gusts), but I think the object itself turned out quite decently.
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