Dark nebula observing

[jetstream]

I thought starting a thread on seeing what folks use on these might help those travelling to dark sites. @scarp15 and @Littleguy80 might have some good ideas here.

I know @badhex has a dark site adventure coming and pre planning can really help when the stars drown out the constellations. Actually goto is a valuable resource here espc when one might not be used to the overwhelming effect that the stars have on a dark night sky.

Thoughts anyone?, Ger

[badhex]

Just saw this after replying to your PM @jetstream - thanks for setting this up! I did actually find Bortle 4 a bit overwhelming at first on a recent trip, as I'm so used to Bortle 8! 

[jetstream]

Personally, observing dark nebula that are located near bright objects can help things out. Defining "bright" objects can also help- the other night I observed the North American nebula, warming up with the OIII then straight to no filtered viewing. There are 2 nice big dark nebs (and more) up there which might be worth a look to identify.

Starting out on dark nebs can be frustrating, but searching out the largest ones can help-if you use the right scope and eyepiece IMHO. Very widefields can help the obviously unfiltered view of these dark treasures.

Edited August 17, 2021 by jetstream

[jetstream]

5 minutes ago, badhex said:

I did actually find Bortle 4 a bit overwhelming at first on a recent trip, as I'm so used to Bortle 8! 

I still get lost in the stars lol! espc near Cepheus for some reason, I've been so lost I just sat in the lawn chair staring up😀

[Littleguy80]

I think Barnard’s E is a great starter dark nebula. You can pick it up in binoculars from dark skies. It’s a nice one where you can really pick it out by the absence of stars.

https://en.m.wikipedia.org/wiki/E_Nebula

Couple of nice articles on other dark nebula you can see. 

http://eastexastronomy.blogspot.com/2010/08/messier-24-sagittarius-star-cloud.html?m=1

https://skyandtelescope.org/astronomy-blogs/dive-into-scutums-dark-nebulae071520151507/

E.E. Barnard’s Atlas of dark nebulae has also been digitised here:

https://exhibit-archive.library.gatech.edu/barnard/

I have a hard copy of this which is a good resource too. 

[jetstream]

1 hour ago, Littleguy80 said:

I think Barnard’s E is a great starter dark nebula

Yes, perfect!

M24 is also a goto object as you mention- I love these great objects with dark nebs in and around them. The Williams Optics 73mm, 430mm fl is so perfect for these Imho!

[jetstream]

@Littleguy80 whats your thoughts about eyepiece selection for dark ones and associated nebs? I like to try all the eyepieces out and note the low scatter ones. I think Joes 430mm f5.9 will take more mag on some bright objects like the Lagoon and Swan than is typically used.

[Littleguy80]

1 hour ago, jetstream said:

@Littleguy80 whats your thoughts about eyepiece selection for dark ones and associated nebs? I like to try all the eyepieces out and note the low scatter ones. I think Joes 430mm f5.9 will take more mag on some bright objects like the Lagoon and Swan than is typically used.

Experimentation is definitely the key as it really varies depending on the target. The Swan and Lagoon are nice with an OIII so I think you can afford to go lower mag to get a larger exit pupil for the filter. One of my favourite views of the Swan was widefield in a 72mm scope with an OIII. I think the eyepiece was a 24mm Panoptic. The view was wide enough to show both the Eagle and Swan in the same FOV. Stunning! Without a filter I’d agree that high mag will probably be needed with that scope. For dark nebula, it’s a trade off of enough mag to gain contrast vs big enough FOV to pick up the edges of the nebula. It really comes down to the size of the nebula and how dark the skies are. 

[jetstream]

51 minutes ago, Littleguy80 said:

For dark nebula, it’s a trade off of enough mag to gain contrast vs big enough FOV to pick up the edges of the nebula. It really comes down to the size of the nebula and how dark the skies are. 

Exactly IMHO.

[jetstream]

B352 and B353 near NAN, B142,B143 near Tarazed and B92 and B93 in the beautiful M24. All these are easily viewed and are nice accomplishments.

There are so many dark nebs in the sky its mind boggling and observing them is great fun.

[John]

Interesting thread

With the exception of B33, the dark rifts in M42 and in the N A nebula, I've not paid much attention to dark nebulae. I'll follow this discussion I think and I'm taking notes !

[globular]

+1 what John said 

[Kon]

Following with a lot of interest. As a beginner with interest in nebulas, what does a dark one appear at the EP, like empty space in a rich star field or does it have any contrast? Do you need a large Dob, filters  or just dark skies (I am at bortle 4 edging 3).

[jetstream]

16 minutes ago, Kon said:

Following with a lot of interest. As a beginner with interest in nebulas, what does a dark one appear at the EP, like empty space in a rich star field or does it have any contrast? Do you need a large Dob, filters  or just dark skies (I am at bortle 4 edging 3).

They dont let starlight through and have a shape, I was observing the dark oblong blotch above Cass the other night naked eye. These do need dark skies but the ones in Aquila are more forgiving.

Filters are of no use and any scope will show them, just lower the mag like you would for filtered use and try them. Our H130 is perfect for them as are many other scopes. Obviously certain scopes will outperform others but it doesnt matter- lower the mag and giver a go!

[jetstream]

Opacity is a good parameter to search Stellarium with as is size https://heasarc.gsfc.nasa.gov/W3Browse/nebula-catalog/ldn.html

"Opacity
A visual estimate of the cloud opacity on a scale of 1 (lightest) to 6 (darkest). These estimates were made by Lynds based on a comparison of the neighboring fields for the particular Palomar photograph on which the cloud appeared. Both the red and the blue prints were used for this comparison. The clouds just detectable on both prints, as evidenced by a slight decrease in the surface intensity of the general field, were designated as having an opacity of 1. The darkest clouds, of opacity 6, were those within which the star density, on the average, amounted to 120 stars per square degree, down to the limiting magnitude of the red photograph. In addition to the minimum number of stars per square degree, the opacity 6 clouds are those which appear to be the darkest - many seem darker than the general background in the neighboring clear regions. The areas of the sky which contain heavy obscuration usually exhibit clouds of several degrees of opacity. In this catalog such clouds are subdivided into areas of the same opacity: thus a single cloud may consist of an area of opacity 3 covering several square degrees and contain within it smaller condenstaions of opacity 6 and areas of hundredths of a square degree. These sections are listed separately, but have been assigned a common value of the parameter ID_Number (q.v.). "

[globular]

LDN is a very long list!  Can’t wait for a clear night to give a few a try.

[jetstream]

9 minutes ago, globular said:

LDN is a very long list!  Can’t wait for a clear night to give a few a try.

Eagerly waiting reports!

[jetstream]

How many of us have tried observing the frustrating Cocoon nebula only to find ourselves lost in that jet black inkspot of B168? Of course there is the multi lobe Triffid nebula... M20 -the lobes defined by B85...

Yes, the dark ones are everywhere.

[scarp15]

Great topic to whet the appetite.

Last time out in pursuit of Dark Nebulae was on a dark sky wild camp close to the England Scotland border, just inside Northumberland. That was Sunday 22 March 2020 with my 85mm frac - and then the world changed. 

On that agenda and on previous was the tricky B34, a small dark neb near to M37. For my encounters, low power, wide field eyepiece and small refractor, or my 16x70 binoculars set up on a monopod are used, always within dark and transparent skies, which on two occasions so far have involved wild camping. The wider the field of view the better, as well as situated upon an observing site with a good low lying vista for hunting dark nebulae such as in Aquila and Sagittarius. This will include the small dark nebula; the Ink Spot Nebula B86, near to and of a similar scale to the rich open cluster NGC 6520 in Sagittarius. 

B37 in Monoceros and not too far from the very difficult Cone Nebula is a possible target. As mentioned by Gerry, B168 near the Cocoon, the Dark Cigar is easy enough. Most dramatic of course is the Great Rift and Cygnus Star Cloud, much of which can be naked eye, such as the Northern Coal Sack. B144; Fish on the Platter is a quite apparent dark nebula in Cygnus in which wide field binoculars can, with a little drifting,  just about frame this quite large - not sure about the fish profile - dark nebula.

As often mentioned and on this thread, Aquila features some of the most visually engaging dark nebula, such as the famous Barnard's E, consisting of B142, B143, darkly etched and makes for a very fine binocular subject. Drifting across, pick up the long curvature of B138 that feeds into B137. Many others besides some of which, not unlike sometimes when lost amidst the Virgo Galaxy cluster, are encountered but not clear as to which ones. Many of Barnard's dark nebulae catalogue are tricky subjects to spot, but they most certainly are integral to a good nights deep sky observing. For my part, I look forward to further encounters hopefully perhaps this Autumn from a wild camp site along the Scottish border.

The link below is Summer Time Dark Nebula: Sky and Telescope.

https://skyandtelescope.org/observing/shadow-play-summertime-dark-nebulae-for-binoculars/

Here  is the Belt of Venus sketch resource for Barnard's E and below is a Deep-Sky Watch sketch resource of B86 along with NGC 6520. Happy hunting.

 

 

[Kon]

@scarp15thanks for an excellent report on observing the dark nebulas. I am waiting for some clear skies and I have added a few things on my to see list from this thread.

[scarp15]

Just as a footnote, I have not to date had much success with pursuing dark nebulae, for which there are quite a few listed, within the vicinity of Cepheus. That is other than I think, within emission nebula IC 1396 Elephant Trunk Nebula. I think Gerry, as I recall you have had a lot more success in this region? 

[jetstream]

B174 in Cepheus might be worth trying...

[scarp15]

8 minutes ago, jetstream said:

B174 in Cepheus might be worth trying...

Yes I attempted that one some time back, it certainly ought to be attainable, will give it another go sometime. 

[jetstream]

The shear number of dark neb can be overwhelming and some are extremely hard to see. I prefer the easy ones lol!  Some like more focal length, some widefield, some like more mag in a small scope etc etc.

My motto?

try everything you have lol!

I gotta repeat- no "special" scope is needed to see these! The 24" dob shows them...as does the 90mm.

[globular]

6 minutes ago, jetstream said:

no "special" scope is needed

But perhaps "special" skies?
I'll try with my 20.4ish and see how I get on.... when my 100% clouds allow.