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M76

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#1 IVM

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Posted 22 December 2012 - 05:09 PM

Going recently through the Herschel objects in Perseus I made the following observation of M76 (Herschel’s I.193, NGC 650-651) that I wanted to share. The observation was made with my 16” Newtonian from the Cherry Springs Dark Sky Park. The following is transcribed and scanned from my field journal.

As befitting a Mechain discovery, it is a complex object even at the modest altitude. At 45x [when my scope works as a 12”] it looks good, like a pinched double. At 225x, the N part has an enhanced, elongated, and flattened NNE edge, and the S part has a broadening and an invagination at the S edge. It reminds me of Mickey Mouse. [Later I was told that my sketch looked like a sitting cat.]

The thick “spiral arm” curving SW from the N end of the “bar” or “apple core” is immediately noticeable and is well separated from the middle of the body. The “arm” that would be symmetric to this one is very subdued, shorter, and barely separable from the body. It may just be a faint extension of the body with a relatively defined edge, rather than an “arm”. Both “arms”, however, are relatively enhanced toward their ends.

OIII filter does little and actually subdues the core, but it makes immediately noticeable the extension of the longer arm toward the star pair in the SW. This extension cannot be held continuously.

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#2 Laurent Ferrero

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Posted 29 December 2012 - 06:45 AM

Hi,

I have observed M76 in september and I saw the same details. The extensions with my 15" was not complete, very similar that your sketches.
This is my sketches :
http://a403.idata.ov...076-T381-md.jpg

#3 IVM

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Posted 29 December 2012 - 12:23 PM

That is a very carefully made drawing! It was interesting to compare the details. A great website too.

#4 Laurent Ferrero

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Posted 29 December 2012 - 04:57 PM

Thank you ! Your website is very rich too, with numerous reports wich give good ideas for deepsky observers.

#5 Scanning4Comets

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Posted 31 December 2012 - 03:00 AM

Wow!

I never noticed this before when viewing M-76. I love deep sky myself and I wonder if I could see the same in my 10" with an Orion Ultrablock filter? I usually use around 100x with my 2" Ultrablock filter and I am thinking that going up to 160x or 210x may bring out more details.

Great post!

#6 Feidb

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Posted 31 December 2012 - 10:00 AM

Now these are what deep sky observations are all about! Very excellent descriptions and drawings. It makes me want to revisit the object again. I may or may not have noticed those features but I'm not at home so I don't have access to my database right now but I'll have to check it later.

Thanks for posting!

#7 IVM

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Posted 31 December 2012 - 11:30 AM

Thank you for the comments! Markus: The bright details at the ends of the core/bar (north-south) should definitely be visible with 10". The extensions east and west are trickier but my bet is they should be visible. O'Meara saw them with 4" from an elevation in Hawaii. While my site is dark, the transparency was not that great at the time of the observation, and, as I noted, neither was the object's altitude. I didn't have a wider filter to compare; the narrowband OIII, as I noted, was not unequivocally beneficial. I imagine it might be under brighter skies. Incidentally, I am pretty certain I hadn't seen these extensions before, although I must have seen the nebula with apertures up to 24". It's unhurried attention that really brings them out.

#8 killdabuddha

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Posted 31 December 2012 - 01:49 PM

Wow!

I never noticed this before when viewing M-76. I love deep sky myself and I wonder if I could see the same in my 10" with an Orion Ultrablock filter? I usually use around 100x with my 2" Ultrablock filter and I am thinking that going up to 160x or 210x may bring out more details.

Great post!


But with the caveat that the Ultrablocks work best at 9x/inch of aperture and lower, yes?

#9 David Knisely

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Posted 31 December 2012 - 02:55 PM

I have seen a little of the outermost "wings" of M76 in my 10 inch on a really dark night with my Lumicon OIII filter, but they are quite faint. I generally like between 70x and 141x for viewing it filtered, although I have gone a hair higher and used my narrow-band NPB filter instead of the OIII. There is a faint triangular patch on the southeastern side of central dumbell and another fainter one off the northwestern side with faint hints of the two loops of nebulosity that connect them with the rest of the nebula. Clear skies to you.

#10 jcco

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Posted 23 January 2013 - 01:24 AM

Hello,

Yes, it is actually quite possible to view the faint extensions of M76 in a 10" scope. It is however heavily dependant on sky quality. I have observed M76 many times and never was able to see them until that exceptionnal night when I made this sketch (using the OIII filter) :

dessin M76

Note that the site where I made this sketch (Valdrôme/France) is not even the darkest I've ever used (Mt Ventoux or Col du Restefond are much better sites) but on this night, seeing and transparency were absolutely prodigious.

To summarize: faint extensions in M76 are quite evident with an OIII filter, even in a 10" scope, as long as you have a really good sky.

Bye,

Jean-Christophe

#11 Starman1

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Posted 26 January 2013 - 01:31 AM

I have seen, with my 12.5", M76 look like a double handled beer stein, or a bar magnet under a piece of paper with iron filings poured on top of the piece of paper. The 'ears' become visible with relatively high power and an O-III filter (violating David K's rule about power and filters).
At lower powers, the best you can do is seeing some extensions away from the ends of the "Gumby-shaped" twin lobe structure.
The most determining factor in the visibility of the 'ears' is a very dark sky and superb transparency.






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