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Nebulae visual variety


Special K

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As I was having some good observations of nebulae last week, it was striking how different those in the same class appear.  This makes me wonder if our eyes can pick up some of the subtle nuances which these fantastic objects have one from another. Are we only bound to varying shades of grey due to surface brightness, conditions etc or can we make out more color?  

For example, to my eye not all emission nebs look the same. When viewing the North American last week conditions were such that the Gulf of Mexico region was in fantastic contrast.  The Nebula was a picture of diffused cotton which I jotted in my notes as not "white" light.  Comparing this with a view of the Swan is striking. The Swan makes me think of a shaft of light and is one of the most intensely white nebs I've viewed.  The Swan is a bright piece of glass whereas the NA is a deep smoke-like plume. Of course pictures show tremendous differences, and the NA is one of those reddish looking ones much like the Rosette and Pelican, or IC410 in Auriga (which was a very dim smoke), which are quite different from the white/blue hues of the likes of Orion.

Planetary nebulae are perhaps easier to distinguish visually because they often have a higher surface brightness and we can sometimes achieve a little color perception. The Eskimo and the Blue Snowball really come through. I compared the mammoth Helix with the Ring Nebula and these two are very similar in structure.   Visually, they are not alike for the very good reason that the Ring is at least three times further distant from us.  The Ring makes me think of a mirror when I view it.  The Helix on the other hand is most elusive and the introduction of any medium magnification washes it away almost completely. 

Just some thoughts and reminiscences on a rainy afternoon about last week's haul!  I can't comment on reflection nebulae as I've not been so lucky to see one.

The Eagle Nebula looked nice and bright and I'd say that the Lagoon always makes me think of that wondrous Orion Nebula!  The Veil was superb with all three major components easily within view. The Eatern Veil gives the impression that a light is falling on that huge globe from an outside source. Magical impressions on a summer nebulae session that ended with views of wintry Pleiades and Orion rising :) 

Clear nebulous skies! 

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I think you're right, Kevin, that there is loads of variety to be seen in ostensibly similar objects.  Recently I've been attracted to planetary nebulae and each is distinct even in relatively modest back garden apertures (now Faulsky has his 20" dob up and running, I am classifying my meagre 12" as "modest").  I've neglected emission nebulae a bit of late - no good reason for that so maybe I'll have to revisit some of the excellent targets you refer to and see how they all differ.

I would think you could see the Pleiades reflection nebula - or at least the bits around Merope - with your kit on a decent night?

Paul

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Really interesting post!

I think there's a huge variety available to the visual observer of faint targets, but it's frequently not exactly handed out on a plate. I try to be confident in my observations, but I find some of the really interesting detail is detected (and I avoid the word "seen") when I note down things that just pop into my head. The more I observe, the more I find I can judge that a fleeting mental impression corresponds to something real.

While on the Eskimo, I wouldn't say I saw anything specific, but I had a repeated mental impression of a texture of flower petals, which seems to match the images (which I hadn't seen prior to observing the target). Long dust lanes spanning random Hershel galaxies give the briefest impression of an eyelash on the lens. Outer arms/lanes of M81 and M31 look like sweeping river bends of a very uniform texture. The Sunflower galaxy has a lovely mottled texture. Various edge on galaxies (e.g. M108) look like chewed sticks; The detail is hard to pin down, but that's the overall impression created by the dusty regions of the galaxy.

I'm going to look out for cotton wool in the NAN now that you mention it! I find these large extended nebulae particularly slippery and it has taken me a fair while to even see them at all.

I've only seen colour in a very small number of brighter planetaries, and only by backing off to very low magnifications to concentrate the light in as small and bright a point as possible. Beyond that it's definitely into into different levels of grey. I don't see the Swan as intensely white but I think I see what you mean; It seems very bright to me too. The Veil always seems a smokey grey, while others are almost an absence of blackness.

For reflection nebs, have you tried M78 or the Iris? These are both quite achievable.

Oh, and don't forget dark nebulae too!

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@FenlandPaul I forgot about the Pleiades and there's been a time or two I might have seen some nebulosity. Not really put the 6" on that yet since I've owned it so I might change my story soon!

@Size9Hex I like the way you summed that up. We're working at the absolute limits of optics and eyesight whether it be galaxies, nebs, or planets, and the differences are minuscule. I sometimes wonder if I under-rate my eyesight and over-estimate my imagination at these extremes. 

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It's worth testing if you're wondering about it. I've previously picked a few targets that I knew nothing at all about and tried to write down as much as I could about them while at the eyepiece - even just hunches. I was as specific as possible to allow comparison against DSS images later and was surprised at how much I could match my notes up to the images afterwards.

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A consideration, and something that can become a bit of a challenge from this time of year onwards, is to try and prevent filters from dewing up. The first time in a while, my OIII filter became too washed out by early Saturday morning to be of any further use.

The Crescent is definitely something that can resemble a brain, a view point shared by others. The North America and Pelican are very much like as described towers and shapes in cotton wool. The Rosette I think can become quite flower like. M42 and M43 is perhaps the most intriguing, as it becomes quite modified between different filters, stark and demonic almost with a H-beta. The first few occasions that I viewed the Veil resembled something that might be photographed swimming in a deep ocean, The California or at least the part that can be glimpsed, looks a bit like a thin silky thread. The bubble (resembling its name sake) is elusive, some occasions it is there meaning that the transparency is very good, others it is not. 

Many emission, reflection and dark nebula though are a continual if captivating challenge to see at all (at least in the UK), when you know that you are in the right spot, yet there is nothing quite apparent other than perhaps star glare or dew formation creating a hint of mistiness. Good transparency, dark skies and dark adaption have to be just right, a frustrating pleasure in equal measure is to try and observe them.  

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2 hours ago, cotterless45 said:

I'm very much taken by the Bilobed 2371-2.For those searching for a variety ,here's an old list, clear skies ! Nick.

Thanks Nick. I love a homemade list to tick and bash through!!!  I'll look up 2371-2.

It was quite clear between clouds last night and on the hunt for Neptune I picked up The Helix from the UK for the first time.  Very washed out compared to Menorca, but same size and shape.  

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Emission nebulae are fascinating and as you've discovered they seem to fall in to different categories but each one is certainly unique.  Apart from (some) planetary nebulae where at low magnification we can see some colour coming through emission and reflection nebulae we're never going to see colour however they have amazing features imho for visual observation and also some are great challenges.

One of my favourites has to be M8 containing clusters and dark nebulae.  Unfortunately for us it's a little low down and only realistically observable for a couple of months - it's worth many repeated visits though hoping to catch it on a night with particularly good transparency and with a UHC filter can really bring out the H-beta regions as well as the brighter OIII.

The really large emission nebulae are difficult but it's an interesting challenge to see if you can define it's shape and take note of any brighter regions within them.  The large emission nebulae need particularly transparent skies and then suitable darkness to stand any chance of observing them.  One particularly challenging one with any light pollution is NGC 281 - Pacman Nebula which I attempted numerous times before I had suitable conditions to view it properly.

I haven't viewed to many reflection nebulae.  M78, M20 and different parts to the Running Man are brighter examples that are not particularly difficult but as filters are of no use you're really at the mercy of needing a decently dark night relatively free from LP and dark adaption.  Because of this, I believe reflection nebulae of the most dfficult or awkward to observe from a typical observing location for the majority of us.

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@scarp15 I totally agree that Orion changes considerably in different filters, and even with no filter making it always fascinating to see.  The Crescent and Bubble have still eluded me so far!  See are very thin so can easily escape detection

@Davesellars thanks for mentioning the Pacman, I had forgot!  This is a prime time of year for it too :) 

Thanks all for the interesting comments.  It's pretty subjective at the business end of an eyepiece!  

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Nothing specific to add to these comments, but wanted to say what a great thread! Thanks for the excellent OP Kevin, and all other posters for some really great observations. @Size9Hex, I really think you have a great method to your observing and recording of objects, specifically about challenging what you think you can see, recording then comparing with images or descriptions later.

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