IC5070 Pelican nebula in RGB plus HA luminance

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timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

IC5070 Pelican nebula in RGB plus HA luminance

#1

Post by timh »

SW200PDS Newtonian F5.0, Baader MkIII coma corrector, CEM70 mount, Baader steeltrack focuser, Pegasus Cube2 focus controller, ASI 120 mm guide camera, Startravel80, f= 400mm guidescope

1) 67 x 110s exposures at gain 124 -10C with an ASI 1294 MC camera and Astronomik UHC filter before post last quarter moonrise under Bortle 6 skies, 0.946 arcsec/pixel

2) 30 x 180s exposures at gain 151 -10C with an ASI 1294 MM camera and Optolong 7 nm HA filter under last ~ quarter low moonlight under Bortle 6 skies. 0.946 arcsec/ pixel

Opportunistic capture using Sharpcap and FWHM / brightness filter during brief cloud gaps over several nights. Guiding using PHD2 multistar, Preprocessing in PixInsight rejecting rogue frames and selecting frames with good brightness (Star number) and FWHM averaging about 2.6. Drizzle x1 integrations.

The HA and RGB images were separately processed (noise reduction, background selection etc) and then, after stretching to non-linear- the Luminance was extracted from the RGB, calibrated to scale consistently with the HA luminance and then the two luminances combined using the Max function in PixMath. The resulting combined luminance was then replaced into the RGB image which was then adjusted with PI curves and tidied up using Affinity Photo.

This was all after spending the past week or so upgrading the Newt by replacing the focuser with the much better steeltrack and replacing an f = 150 mm guidescope with an f 400mm guidescope located right above the main scope on the tube rings.

The new guiding setup and focusing is much better. PHD2 multistar seems a big improvement - guiding generally better than 0.7 arcsec RMS. Anyway something worked better because the final image is sharper than any I have had previously of this object with PI subframe slector estimating the final integrated image at ~ 3.3 arcsec.

I like the object itself which is an HII area about 1800 ly away. As pointed out by Menno in one of his images from last year the Herbig Haro object HH 555 is very evident at the end of the longest dark pillar of the dark dust cloud. When I look at objects like this I have always rather assumed that at least some of the large bright blue and white stars in the frame are responsible for the UV ionisation of H and erosion of the dark material into pillars. Interestingly it seems not since most of those bright stars that you can see (e.g prominently Cyg 56 and 57) aren't at the right distance or are the wrong type and the real main culprit lies virtually invisible except in IR and lurks within the main dark cloud separating the NAM from the Pelican. It is probably a mid-O type star with the catchy name ", 2MASS J205551.25+435224.6" https://www.aanda.org/articles/aa/abs/2 ... a1788.html

Tim
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PelicanCapture.JPG (128.91 KiB) Viewed 725 times
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Menno555
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Joined: Mon Apr 20, 2020 2:19 pm
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Re: IC5070 Pelican nebula in RGB plus HA luminance

#2

Post by Menno555 »

Nice capture Tim!
About star placement. I was thrown off in the beginning by a statement I did read that stars you see in captures, are all in front of the object. I failed to realize though that that only applied to objects outside the Milkyway :)
With "close by" objects like this, it's indeed that stars can be in front or behind them. I tend to use Aladin with the NED catalogue now to check :)

Menno
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