The Cat Eye Nebula

[orion f6.3]

Just had my first good view of The Cat Eye Nebula. Listed as a green tinge but was a nice shade of green to me! Always a nice end to an Observing night to find something new with just a DOB and not a GOTO in sight! But as a test I compaired the central star to the Polaris companion star of 9mag as my collins atlas of the night sky lists the The Cat Eye Nebula central star as 9.5mag it seamed a little dim, looked in Caldwell objects and its listed as 11mag ! any ideas

[qcdougn]

Hi,

I can't help on the magnitude question. But, wonder if you saw my images posted here on July 16th of M94-The Cats Eye.

Doug

[FLO]

Hi Orion,

StarryNight lists the Cat Eye nebula as magnitude 9 ( Cats Eye nebula 8.8 ).

(Odd, it doesn't show an image when zoomed in :scratch:)

[Astroman]

The discrepency is usually a color magnitude, Orion. Lists generally show the visual magnitude, but sometimes they show either the "photographic" magnitude, or the "blue" mag. The Coldwell listing is most likely a surface brightness mag.

"Visual" is in the yellow/green range of the spectrum and is the area of most sensitivity for the human eye.

"Photographic" or "blue" are shorther wavelengths. The photo designation is an older one aimed at the more sensitive range of film emulsions. The blue photometric filter is notorius for doubling or more exposure times for mages. (Evil, nasty filter!)

The surface brightness mag takes the size of the object into account. An extended object will have an overall brightness, but since it has size, that brightness is spread out over the area, effectively reducing the amount of light reaching your eye. A good example is M33-bright on the total mag scale, but so spread out, it's hard to see.

Hope this helps.