Gum 15 in colour

[Placidus]

We recently did Gum 15 in H-alpha and OIII, and confirmed that one night with a 20 inch yielded no detectable OIII.

But excellent images by Lee Borsboom, Geoff Smith, Paul Haese, and ESO show that there is lots of beautiful blue reflection nebulosity.

The ESO shot (https://www.eso.org/public/images/eso1420a/) is curious in that it seems to show too much green in the nebulosity. Never thought we'd hear ourselves saying that. But otherwise, we aimed to produce a similar effect to the ESO shot.

Herewith 17 hours total exposure over three nights, peering between clouds.

Big one here
(https://photos.smugmug.com/Category/Dark-nebulae/i-DLMMcmb/0/352b1fcf/O/Gum%2015%20Lum%202hrs%20RGB%205hrs% 20each.jpg)

FLI PL16803 on 20 inch PlaneWave. Lum 2hrs, RGB 5 hrs each, in 30 min subs. All scope and observatory control software, firmware, electronics, and processing software designed built written in house by us. Nothing purchased pre-cooked at the restaurant.

For those who've not had a go at it, this nebula is ridiculously faint. It takes a lot of exposure to get the noise down.

It looks as if the blue reflection nebulosity is in a different plane to (and seemingly in front of) the red emission nebulosity.

Doing natural colour has also brought out quite a pretty star field, with some hot blue cluster stars, a few lovely red giants, and the distant field of cooler redder Milky Way background stars.

Cheers,
MnT

[Peter Ward]

To quote Luke Skywalker's dad: impressive. very impressive. :thumbsup:

[Andy01]

That's really nice team, reminds me of Sturt's Desert Pea. :D
Interesting writeup too, good on you for persevering and doing your research!
Top stuff. :thumbsup::thumbsup:

[multiweb]

:eyepop: That's quite a treat Mike. Love the colours and details. It matches the ESO shot one to one really well. The colors in the dark neb at 8 o'clock reminds me of the top of the horse head and its shape the central ridge in NGC6188. Starfield depth and color are quite impressive. One for the extension. :thumbsup::thumbsup::thumbsup:

[rustigsmed]

yep, excellent stuff - beautiful image.

[AdamJL]

what a beauty :)

[gregbradley]

That's a wonderful vista. Love the faint blue wispy O111 filaments.

Greg.

[PKay]

Great work M&T

You certainly have the framing right.

It's encouraging to see how it should be done.

Maybe add a little green at the top :)

[strongmanmike]

Arhem...:whistle: sooo, whooo didn't read the post again??...:lol: (luv ya Greg :love:)

Lovely lovely lovely M&T :clap:...in fact here, have one of these :prey2:

What a magnificent looking gem it is!

Who did the colour processing? Nice work ;)

Mike

[Placidus]

Peter, Andy, Marc, Russell, Adam, Greg, Peter, Mike,


Thanks so much for the encouraging words.



MBJ did the boring bits of the processing. TBJ did the colour balance and final brightness and contrast.

[marc4darkskies]

Wow M&T! That's an absolutely gorgeous image! :thumbsup: :thumbsup: The richness of the colour is just superb! I want one! :)

[strongmanmike]

...how romantic it must be for you two :love2:...can't be too many other couple's out there sharing the joy of astrophotography/imaging the way you two do :cheers:

Mike

[Placidus]

Thanks Marcus!



:love2:


While I think of it, Trish:


- starts the generator
- starts the computer while I zip up ladders to take off the dust covers
- opens the dome, cools the cameras, finds a synch star and does the synch.
- I then usually find our target for the night.
- Trish does a focus run.
- We then write the script together, checking each other's work for mistakes.
- Then we run the script, and tip-toe back to the homestead to watch a movie.


In the morning it's my job to go up to the observatory to:
- collect the booty
- put the covers back


Meanwhile Trish makes the urgent resuscitation coffee. My biggest job is getting out the multimeter, soldering iron, and pointy wizard cap when things stop working.


Best,
Mike

[strongmanmike]

Hey look!...I found an old photo (https://cdn.mos.cms.futurecdn.net/DXHXAKSzSXUP3Nm74pD3Am-970-80.jpg.webp) of you two...

:D

[PKay]

Very funny Mike

Whilst your their, I was wondering about the missing 03 in the image above.
Blue has turned up in the filaments using wide band pass.

Could this mean blue shift?
Is Gum15 moving toward us?

[Placidus]

Auntie Marie and uncle Pierre?



It is of course possible that the blue is 500 nM OIII which has been doppler shifted out of the 3nM bandpass, but is still visible in a broadband filter. But the shift would have to be of the rough order of 3/500 = 0.6% of the speed of light. That's about 40 times higher than the rate Andromeda is moving towards us.'


The likely explanation is that the blue is broadband starlight rendered blue by being scattered off dust, much like our sky is blue.

Edit: Just realized that the proposed doppler shift would have to be hugely more than that. The [OIII] is about 500 nM, or blue-green, but the image shows it to be a pure blue with very little green, so at the very most 480 nM, a shift of over 4%. That would put the H-alpha way out of its bandpass, which we did not see. So already not doppler shift. Perhaps more like 400 nM. Taking that into account, it would give a speed toward us of 25% of the speed of light. At a distance of 1500 light years, it will be upon us in only 6000 years. We'd better duck. :scared:

[PKay]

Well calculated M&P :)

What about the possibility of a cosmic explosion?

That might account for the high shift.

[Ryderscope]

That is an intriguing field MnT. The wisps of blue appearing to emanate from the nebula and floating upwards into the vastness of space with apparent shock fronts trying to work their way across the screen. Fantastic :thumbsup: :thumbsup: :D

[Placidus]

Thanks Rodney!

Starting to see that these "young" low-energy star-forming regions are better in RGB than in narrowband. The Trifid is a tricky one, because it is a mixture of reflection nebulosity and complex emission nebulosity with bits of this and bits of that which show up well in narrowband. Then there's just about anything in the LMC or SMC, illuminated by OB stars and supernovas a-plenty, which work best in SHO.

[Paul Haese]

Nice image M&T. Thanks for the mention and I can concur this object takes a fair bit of integration to get a smooth result. It is a fascinating looking object with the plumes of dark nebula with hints of luminosity showing quite well and giving a 3D perception. Looking at your result I wish I had done some OIII too as my image only shows the reflection from the blue and luminance filters. I like the blue intensity in your image, colour saturation and the contrast of the image. Well done.

[strongmanmike]

Hmmm?..so, just how many people don't read posts properly...? :scared:

Mike said: "and confirmed that one night with a 20 inch yielded no detectable OIII."....

Maama mia! :rolleyes: :lol:

[Placidus]

Thanks Paul. As Mike S mentioned, we did try a whole night of OIII on this beast, and found only blackness. So what we are seeing here must be reflection nebulosity. I'm guessing that means that the object is either in a relatively low-energy environment (not so many super-hot stars), or that where there are super-hot stars, the gas is too dense.

[Paul Haese]

Oops, I thought I read that Mike had captured OIII. I guess we all make that mistake sometimes.

[topheart]

A difficult object done really well!
Cheers,
Tim

[Placidus]

Thanks Tim.

[pkinchington]

Lovely image - your perseverance paid off :)
Cheers Kanga