Star formation by the Wizard? RGBHa image

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timh
Posts: 272
Joined: Mon Aug 26, 2019 5:50 pm

Star formation by the Wizard? RGBHa image

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) 81 x 110s exposures at gain 124 -10C with an ASI 1294 MC camera and Astronomik UHC filter under moonless Bortle 6 skies, 0.946 arcsec/pixel

2) 20 x 180s exposures at gain 151 -10C with an ASI 1294 MM camera and Optolong 7 nm HA filter under waning near full gibbous moon and Bortle 6 skies. 0.946 arcsec/ pixel

Capture using Sharpcap and FWHM / brightness filter. FWHM of individual frames 2.5 to 3.0. Guiding using PHD2 multistar, RGB frames preprocessed and stacked in PixInsight. In the case of the HA I just used the the 60min autostack .PNG file straight from Sharpcap 4.0.

The HA and RGB images were separately processed (noise reduction, background removal 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.

Although only 1 hour of capture, the HA luminance added a great deal of clarity to the image of the nebula. The HA addition seemed to work fine just using the ready-stacked SC autostack (although I will also try doing it 'properly' to see if all that work in preprocessing adds much). May try adding O3 but I suspect that the UHC / RGB has already caught most of what is to be seen there? I think that the orangy/ red is mainly a mixture of HA and more light scattering by dust and the whitish, yellow and pink where there is both OIII and HA (including H beta etc) and rather less light scattering - however not so much OIII signal as to see a bluish tinge as in Menno's image below?

Notably the addition of the HA to the luminance has made the eponymous Wizard of NGC7380 much more apparent. If you examine the wizard's mouth closely there appears to be a bubble with a newly formed star inside. A stream of bright stars also appear to arc away from his mouth. Clear evidence here therefore that stars are formed by cosmic wizards when they blow bubbles ?

TimH
Attachments
aaNGC7380_Newt_Baader_UHC_13_170821_81x110s_gain124_integration_DBE_PCCcol_SCNR_50_MLT_strmsk_TRAN_curves_MLT_starlet_plusLUMfron 20x3min of fullmoon HA_240821_PX.jpg
aaNGC7380_Newt_Baader_UHC_13_170821_81x110s_gain124_integration_DBE_PCCcol_SCNR_50_MLT_strmsk_TRAN_curves_MLT_starlet_plusLUMfron 20x3min of fullmoon HA_240821_PX.jpg (970.53 KiB) Viewed 120 times
timh
Posts: 272
Joined: Mon Aug 26, 2019 5:50 pm

Re: Star formation by the Wizard? RGBHa image

Post by timh »

Just for completeness I took the above a bit further by seeing how much improvement could be had by adding more HA and also about 2h of O3 taken under dark moonless Bortle 5 skies.

So conditions as above except now with..

2) 39 x 180s exposures at gain 151 -10C with an ASI 1294 MM camera and Optolong 7 nm HA filter under waning near full gibbous moon and Bortle 6 skies. 0.946 arcsec/ pixel

3) 39 x 180s exposures at gain 151 -10C with an ASI 1294 MM camera and Astronomik 6 nm O3 filter under moonless Bortle 5 skies. 0.946 arcsec/ pixel

The HA , O3 and RGB images were separately processed (noise reduction, background removal etc) and then, after stretching to non-linear- the Luminance was extracted from the RGB, and, along with the O3, calibrated to scale consistently with the HA luminance and then the three 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 as well as starmask/ morph in Pixinsight to reduce stars.

Image A was processed just as above. In the case of Image B some of the O3 image was combined back into the G and B channels along with some of the HA into the red channel and carefully balanced using the PI NBRGB script.

Image A seems to provide the sharpest and best detail of the nebula. Using the NBRGB function seems to very slightly degrade the image by adding back in more noise but provides clearer delineation of where the OIII is localized in this particular nebula -- in front of the wizard's face. So on balance I like image B better which better highlights the OIII. Significant OIII seems quite unusual in these types of emission nebula objects. Unlike planetary nebulae, presumably not many have stars sufficiently hot to efficiently collisionally excite the O2+ and/ or less oxygen is present or it is too diffuse?


Tim
Attachments
Wiz_pair.JPG
Wiz_pair.JPG (155.01 KiB) Viewed 38 times
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