M27 11th july 05

[OXO]

Took this image last night after much a Do, it's 20 frames of 20secs with the 102st and toucam.

I found the seeing to be about 6/10 there was a slight white hue to the sky but was quite steady. The effects of light pollution around my area tends to washout m27 at the moment i find other dso's like m57 to be brighter :shock: .

James

[AndyMac]

Nice image James. It's interesting how our perceptions of objects differ. I've never found M57 to be brighter than M27 through my 11" scope - but there you have it.............

[OXO]

M57 is supposed to be mag 9.5 whilst m27 is somehitng like 7.8 doesnt make mush sence to me either only that it must be the light pollution...

James

[AndyMac]

The magnitude values will be on the assumption that the light from each object is condensed into a single point of light. Don't forget that, although M27 has a higher value, its light is spread out across a wider area.

[OXO]

Yes that is true andy just figuring out why so many people like yourself say that M27 is so much brighter than M57...

James :?:

[AndyMac]

Dunno whether the bigger aperture has anything to do with it - or the filter I use perhaps blocks out more of M57's light.

...But M27 is definitely both bigger & brighter.

[AndyMac]

Hmmm...... my book A Visual Atlas of Deep Sky Objects by Roger N Clark seems also to contradict my last post. The mean surface brightness for the Ring is given as 17.9 magnitudes per square arc-second whereas the Dumbell's mean surface brightness is only given as

20.8 magnitudes per square arc-second.

BTW this book is an excellent guide to the visual appearance of the better known DSO's. A real pleasure to read!

[OXO]

A Visual Atlas of Deep Sky Objects by Roger N Clark i will keep a keen eyeout for that andy prob need to order it through a book seller though.....

I would still maintain it's the light pollution and at what angle its coming from(degree's etc) could be completely wrong but there you go..

James

[AndyMac]

The book was published in 1990 James. Not sure if it's still available. May be worth checking with the likes of Earth & Sky booksellers. The ISBN is 0-521-36155-9 & the publisher is Cambridge University Press.

[Ant]

it's the similar situation with M101 and M51.

M101 Mag 8.5 size 46'

M51 Mag 8 Size 18'

M51 is an easy object to spot at the EP, but I've never managed to even find M101. Yet their magnitudes are almost the same.

I would say that IMO M57 is much brighter, but it's due to be more compact and having a higher contrast.

Ant

[russ]

Amazingly i've actually seen M101 from the backgarden, the night i imaged it. Even more amazing was how easy it popped into view. The other strange thing that night I couldn't find M63. Yet i've found M63 countless times and pretty easy object. Just couldn't find it.

I think you're right Ant, M57 is a bit brighter and one of the easiest objects to find.

Russ