Near real-time observing of bright nebulae

[Martin Meredith]

Here are some bright nebulae I observed last week, all using 15s subs live stacked in LodestarLive. Filters are probably necessary to get the best views of some (or all) of these objects, but I wanted to see what the unfiltered mono camera was capable of producing.

First, NGC6888, the Crescent nebula. I was happy to capture at least part of the nebulosity but was fighting a 75% moon which didn't set for 2-3 hours after this shot (SQM 19.3 skies). But what struck me most watching it build up is that the beauty of this field is not simply the wraith of nebulosity embedded in a rich star field, but the 4 or 5 brighter foreground stars, of which 3 appear as doubles.  Two are catalogued in the Washington Double Star list. OS401 (Otto Struve) has components with mags 7.2 and 10.7, separated by 13.8". The pair SLE 955 has mags 8 and 13 with a 14.9" separation. Also labelled are a couple of other members discovered by SLE (anyone know who this is?). Pair 956 is an almost equal pair (11.9, 12.8) separated by 9.9", while pair 965 is an equal pair of mag 12.5 stars with a 7.5" separation. V1770 Cyg is variable but not listed as a double.

Taken a couple of days earlier with a setting moon, this is a shot of the Cocoon, the first time I've seen this object and not the last. It really is a spectacular sight with its inner sanctum revealing one bright and many faint stars. It appears to be surrounded by obscuring dust too. Also marked is an unexpected find: a faint background galaxy (PGC 167593 mag 18.2). It must surely be quite rare to see a galaxy in this part of the sky given the density of stars and dust?

Next, part of the Western segment of the great Veil supernova remnant. I've observed this visually with an O-III filter and it looks superb, so I was interested to know what an unfiltered view looks like with the Lodestar. Both arcsinh and  x^0.25 scaling produced good views of the Veil.  

Next, some nebulosity surrounding two pairs of bright stars (looks like a cat's face to me) and an open cluster, Dolidze 8, in Cygnus. These are known as Van den Bergh 132 and 131. 

Here's part of the "War and Peace" nebula (NGC 6357) in Scorpius. I was really struggling with this low target to bring out the fainter extensions while keeping the stars from too much bloat, and haven't really succeeded. I think it is worth a visit with a filter and a wider FOV at some point.

Finally, M17, the Omega Nebula in Sagittarius. This is a full 4 magnitudes brighter than War and Peace, and it shows! This reminds me of a cloud underlit by significant light pollution. 

Note that in many cases these are quite long stacks, but they accurately represent the end product of a real-time observing experience during which the image continually improves with 15s updates. For me nowadays "total exposure length" is almost unimportant: I observe for as long as I like (usually 15-20 mins per target including finding and framing). None of this would be possible without robust live stacking.

thanks for looking

Martin

[xtreemchaos]

great set of images Martin.thanks for sharing..charl..

[arkosg]

Martin,

Amazing as usual!  I'm very impressed with how tight and well focused your stars are, especially in the Cocoon Nebula shot.

Is this your seeing, your scope, the mono X2, your skill at focusing, or something else?  I usually start to see star bloat, and never get things quite as crisp as you do!

Cheers,

- Greg A

[Dom543]

Very nice shots Martin!

Are you using any of the non-linear DR options?

Thanks,

--Dom

[Martin Meredith]

Thanks guys.

Greg, I wish I could get tight stars all the time! I do find the Newt is capable of producing decent star images, but at f/4 collimation is important and since I was transporting the scope and setting it up each time it was necessary to tweak collimation each evening, so that's a variable too. Maybe that is what made a difference on the 26/6 images which are particularly tight. I've started to observe open clusters and they're great targets to help hone adjustments. I haven't yet experimented collimation will observing using the Lodestar (I use a Catseye to do that), but I'd like to try that too. Re focusing, I spend about 5 mins or so on this and very occasionally refocus during the session. I don't yet use a mask but that's something else I'd like to try. 

Dom, all of these shots use x^0.25 or arcsinh (the ones that say root are x^0.25 -- not sure about the others). I find x^0.25 slightly easier/smoother to manipulate but occasionally see a larger benefit with arcsinh on certain objects, though I haven't discerned a pattern yet. 

Martin

[aparker]

Lovely images Martin. I also really enjoy the veil as a visual subject with O III filter. I'm going to have to give it a shot with the Lodestar a bit later in the year when Cygnus is higher in the evening.

[orion25]

Wonderful, Martin. A beautiful eye into the cosmos 

Reggie

[Paul81]

A great session Martin! Some of those objects are tough to observe, I remember exploring the area round the Crescent and Cocoon nebulae last year. A OIII definitely helped.

I am like you, total observing length depends on how captivated I am by the view, its not unusual to have racked up dozens of exposures without realising!

Missing astro at the moment, it doesn't really get dark at a sensible hour, but sods law there have been many clear skies!! 

[laudropb]

Great images. Thanks for sharing