Object of the Week July 19th, 2020 - NGC 6905 The Blue Flash

[Dragan]

NGC6905 – The Blue Flash
Henize 2-466
PK 61-9.1

Delphinus

Planetary Nebula

RA 20h 22m 23.0s
DEC 20 06' 16"

Magnitude 10.9
CS mag: 15.7
Size: 72.0"x 37.0"



When I began reviewing objects for this week’s OOTW, I rummaged through my notes looking for an object that would qualify as ‘eye candy’. I wanted to provide a nice visual treat this week, particularly in large scopes. Needless to say, I was a little surprised to discover that my object this week had never been previously selected as an OOTW.

NGC6905, also known as the Blue Flash Planetary, sits in the northern constellation Delphinus the Dolphin near the borders of Vulpecula and Sagitta. It was discovered by Sir William Herschel in 1784 using his 18” f/13 speculum mirrored telescope. Herschel described the planetary as “perfectly round, pretty bright and pretty well defined”.

Visually, 6905 is a delight. Able to be seen in all manner of telescopes, the Blue Flash best resembles its namesake from dark skies with larger scopes. It’s blue-green hue starts to reveal itself in scopes larger than 10”. The planetary is a bright, slightly elongated glow superimposed by an isosceles triangle of ~11^th magnitude stars.

My last observations of this object came in 2015.

July 3^rd, 2015. In my 25” at 315x and 394x, my notes reveal a “blueish glow inside a triangle of stars, round but slightly elongated with some mottling. Brightening on its edges. CS readily direct vision. Reminds me of M27. NPB and OIII both brightened it. Great view!”.
14OCT15 30” f/4 OMI EVO Eastern and western edges (mostly eastern) quite pronounced with northern southern edges less defined. Overall appearance reminds me of M27. Mottling throughout central regions. CS direct vision. Rather light blue object but les so than 7662 I think.”

NGC 6905 is a wonderful object visible in all manner of telescope apertures. It’s a beautiful object that sits in a rich field of stars and proves to be quite the sight in larger scopes.
As always,

“Give it a go and let us know!”

NGC6905 LRGB crop_Graham Winstanley.jpg
©Graham Winstanley

[obrazell]

Actually Dragan you covered this yourself in 2016 http://www.deepskyforum.com/showthre...The-Blue-Flash :-)

Owen

[Dragan]

Actually Dragan you covered this yourself in 2016 http://www.deepskyforum.com/showthre...The-Blue-Flash :-)

Owen

Wow did I just screw the pooch!

It's so weird. I did a search and that thread isn't revealed. I'll need to look into that. How did you find it?

[Dragan]

Wow did I just screw the pooch!

It's so weird. I did a search and that thread isn't revealed. I'll need to look into that. How did you find it?

I figured it out. My original thread has the object listed as NGC6905 - no space. If you search for "6905" in our search function, NGC6905 doesn't appear. So I didn't see it. I just assumed it hadn't been written about. UGH. Sorry for the repeat everyone!

[obrazell]

I have all the OOTW in SkyTools lists and can search on an object and see if is already covered in an observing list :-)

Owen

[Raul Leon]

Hi here's my observation from 12/27/2011: ngc 6905 is a planetary nebula in Aquila; magnitude: 11 size: 72"×37" ; roundish; slight elongation, framed by two fairly bright stars,central star easily seen, mottled area within the disc, slight blue color observed, no filter used. I used a 7mm Nagler at 226x with my 14.5 Starstructure Dob f/4.3ngc 6905.jpg

[wvreeven]

A paper with a detailed spectroscopic study of both the nebula and its central star has appeared:

https://arxiv.org/abs/2110.09551