Campbell's Hydrogen Star

[Fred Ley]

With the constellation Cygnus being one of the major constellations that dominate the summer sky I would like to point out an obscure little planetary nebula. Campbell’s Hydrogen Star, which is, located about 2.5° north of the well-known double star Alberio. It is not shown on many contemporary atlases. The Burnham’s Handbook makes no mention of this planetary in the Cygnus section. In my Deluxe Edition of Tirion Sky Atlas 2000 a small planetary is shown in the vicinity. I do not know if it is referring to this particular planetary nebula.

 

In Steven J. Hynes book Planetary Nebula, the following information is given for this planetary on page 158.

 

Coordinates for 2000.0 are

RA 19h 34.76m

Dec +30° 30.6¢

The nebula itself is given a magnitude of P 9.6 and V 11.3

It is listed as a type IV and having a diameter of 8 seconds.

The star is magnitude 10.00 and its spectral classification is WC9. The name is HD 184738.

 

The following information and chart are from skynightinfo.com and seems to succinctly sum it up.

 

“Herschel never saw PK 64+5.1, nor does it belong to the NGC. Its position is not plotted on many sky atlases and most modern observing guides let it pass without notice. What is this planetary?

In 1893, the American astronomer William Campbell was observing through a visual spectroscope at Lick Observatory, when he happened upon this strange object in southern Cygnus. From its spectrum it was clearly not an ordinary star, but rather a tiny planetary nebula. Today we know it as Campbell's Star, although it is labeled on most maps as PK 64+5.1, a designation from the Catalogue of Galactic Planetary Nebulae.

Even though it is visible with small telescopes, Campbell's Star is only recognizable as a planetary when viewed with moderately high magnification. Because PK 64+5.1 is only 5" across, an 8-inch reflector at 200x reveals just a small, 9th-magnitude grayish disk. Larger telescopes equipped with an OIII filter will also show the nebula's 11.3-magnitude central star.”

 

Please take not that there is a subtle difference in the magnitude and diameter as given by the book and the web site.

 

I enjoyed looking at this object for the first time through a rather large telescope, the historic 60-inch on Mt. Wilson, in 2003. Naturally the bigger the instrument the brighter the image and the better the resolution-provided that the atmosphere is stable.

 

If anyone observes this little fellow I would be interested in hearing about their experience.

 

-Fred

[Μανούσος]

Fred,

This is very interesting object. I have already added in my object list for the next observing session. We all thank you very much.

[Nompi]

Fred,thank you very much,I hope to watch it with my new telescope...

[Fred Ley]

Glad the two of you found this of interest.

 

-Fred

[Μανούσος]

Fred,

I had a problem of identifying the star. I had two failed attempts, of the two observing sessions that I had the last weekend. I 'm sure that I was in the field, but the background was very rich in stars and the identification was impossible. I've tried also OIII and UHC filters but with no result.

[Fred Ley]

Hi Manousis,

 

I just noticed that Dimitri Kolovos has posted an image of the star today. It came out really nice. Perhaps you could get in touch with him and see if he has any pointers he could share with you on locating it.

From what I have read, the OIII filter is the filter to use on planetaries. I don't know what kind of sky conditions you have in your area, the dark seeing adaptability of your eyes and aperture of the telescope that you use. Naturally they all play a role. Perhaps you could use the image that Dimitri took as a guide. I don't know what the actual field of view is, but one might be able to determine it by using an atlas. Hope that you locate it.

 

-Fred

[alepohori]

I saw it at Kitheronas mountain, my experienced co-observer giorgosgr saw it too, but we didn't realize it was it since we didn't use the appropriate magnification. We noticed that Campell's star doesn't correspond well in OIII filter!!!!, that's why we could not be absolutely sure for seeing this! I was trying for a long time, so i am sure i was just at the right field!! The dimikolgr's photo verified our observation!! Thank you Dimitris!!!!